Envionmental Systems and Societies
TOPIC 1: FOUNDATIONS OF ENVIRONMENTAL SYSTEMS AND SOCIETIES
Topic 1.1: Environmental Value Systems
Knowledge and Understanding:
Environmental value system (EVS): a worldview that shapes how a person or group of people perceive and evaluate environmental issues
EVS may be influenced by culture, religion, economic factors, experience, education, media, and socio-political contexts (inputs), and involves a set of interrelated premises, values and arguments that can generate consistent decisions and evaluations (outputs)
There is a spectrum of EVSs from ecocentric to anthropocentric to technocentric.
An ecocentric viewpoint integrates social, spiritual and environmental dimensions into a holistic ideal. It puts ecology and nature as central to humanity and emphasizes a less materialistic approach to life with greater self-sufficiency of societies.
Ecocentric prioritizes biorights.
It emphasizes the importance of intrinsic value.
It promotes self-restraint in human behavior.
An anthropocentric viewpoint argues that humans must sustainably manage the global system.
This might be through the use of taxes, environmental regulation and legislation.
Debate would be encouraged to reach a consensus pragmatic approach to solving environmental problems.
Anthropocentrism prioritizes human rights and needs.
It sees nature as having instrumental value.
A technocentric viewpoint argues that technological developments can provide solutions to environmental problems.
This is a consequence of a largely optimistic view of the role that human ingenuity and science can play in addressing issues.
Scientific research is encouraged in order to form policies and to understand how systems can be controlled, manipulated or changed to solve resource depletion.
A pro-growth agenda is deemed necessary for society's improvement.
Technocentrism prioritizes technological solutions.
It has a strong faith in science and technology to solve environmental problems.
It also sees nature as having instrumental value.
There are extremes at either end of this spectrum (deep ecologist to cornucopian), but in practice EVSs vary greatly in time and culture and rarely fit simply or perfectly into any classification.
Different EVSs lead to different interpretations and actions in response to environmental components of the biosphere.
Historical Influences on EVSs:
Significant historical influences on the development of the environmental movement have come from literature, the media, major environmental disasters, international agreements, and the influence of environmental pressure groups.
Education and encourages self-restraint in human behaviour.
Humans' environmental concerns may rise significantly during times of social or economic upheaval.
Range of EVSs (More Detail):
Cornucopians believe
The world has infinite resources to serve humanity's needs
Any environmental problem can be solved through technology and inventiveness, leading to continually improving living standards.
Optimistic about the future
Favor a free market and capitalist system with minimal government control.
Environmental managers believe
See the Earth as a garden needing tending – the stewardship worldview.
They have an ethical duty to protect and nurture the planet.
There are problems that require government legislation and local solutions.
Optimistic that economic growth and resource exploitation can continue if carefully managed.
Self-reliance soft ecologists (ecocentrist) believe
Small-scale, local community action and the power of individual actions.
View the Earth as a living planet and advocate for self-reliance and decentralization of political power with community involvement.
Prioritize ecological wisdom and sustainability
Distrust large-scale technology and centralized government.
Solving environmental problems requires a fundamental shift in attitudes and values and a reduced impact on nature.
Deep ecologists (ecocentrist) believe
Nature has intrinsic value – value for its own sake, not just for humans.
Advocate for biorights – the universal rights of all species and ecosystems to exist and flourish.
Humans have no right to interfere with nature except to satisfy vital needs.
Advocate for a substantial reduction in human population and a radical restructuring of society towards small-scale, self-sufficient communities with restricted impact on the natural world.
Topic 1.2: Systems and Models
Knowledge and Understanding:
A system is a set of interrelated parts working together to form a complex whole. Systems can be living or non-living. Examples include a bicycle, a pond, an ocean, a school, or planet Earth.
Systems can be open, closed, or isolated.
Open systems exchange both matter and energy with their surroundings. Most ecosystems are open systems. For example, energy enters as sunlight and leaves as heat. Matter is exchanged through inputs like precipitation and outputs like water flow.
Closed systems exchange energy but not matter with their surroundings. The Biosphere 2 experiment was an attempt to model a closed system. On Earth, the global water and carbon cycles can be considered essentially closed systems.
Isolated systems exchange neither matter nor energy with their surroundings. A perfect isolated system is a theoretical concept and does not really exist in nature, although the entire universe might be considered one.
An ecosystem exchanges both energy and matter across its boundary with the surrounding environment, thus functioning as an open system.
Transfers occur when energy or matter flows and changes location but does not change its state. For example, water moving from a river to the sea.
Transformations occur when energy or matter flows and changes its state or form. For example, light to chemical energy in photosynthesis, or liquid water to water vapor in evaporation.
System diagrams can represent these flows and storages using boxes (for storages) and arrows (for flows/transfers and transformations). The size of the boxes and thickness of arrows can indicate the magnitude of storages and flows.
A model is a simplified version of reality that can be used to understand how a system works and to predict how it will respond to change. Models are often used to explain complex systems.
Types of models: physical models (like a model volcano), conceptual models (like a food web), and mathematical models (using equations).
Strengths of models: can make predictions and simplify complex systems visualize small or very large entities, help in understanding interactions, and be applied to other similar situations.
Limitations of models: may not be totally accurate (oversimplification), predictions may not be reliable, they rely on the expertise of the model developers, different models of the same system may produce different results, all models make assumptions which, if wrong, will affect the accuracy of the model, quantitative models might be precise but lack realism, while qualitative models might be the opposite.
Gaia Hypothesis:
The Gaia hypothesis views the Earth as a single, self-regulating living system. This perspective suggests that the biosphere and the physical components of the Earth (atmosphere, oceans, land) are tightly coupled and evolve together to maintain conditions suitable for life.
Strengths: provides a different perspective on the Earth as a whole and emphasizes the interconnectedness of living and non-living components.
Weaknesses: sometimes seen as untestable and not providing clear mechanisms for regulation.
Topic 1.3: Energy and Equilibria
Knowledge and Understanding:
Energy flows through ecosystems. Most ecosystems are open systems, exchanging both energy and matter with their surroundings. Energy enters primarily as sunlight and leaves as heat.
Matter cycles within ecosystems. Unlike energy, matter is conserved and recycled within a system.
Transfers involve the movement of energy or matter from one place to another without a change in form. Examples include water flowing in a river or the movement of a herbivore from one feeding patch to another.
Transformations involve a change in the form or state of energy or matter. Examples include photosynthesis (light energy to chemical energy), respiration (chemical energy to heat energy), and the change of water from liquid to vapor (evaporation).
The laws of thermodynamics are important in understanding energy flow:
The first law of thermodynamics (law of conservation of energy): energy cannot be created or destroyed, only transferred or transformed. In ecosystems, this means the total amount of energy entering a system equals the total amount of energy leaving, plus any energy stored within the system.
The second law of thermodynamics: in any energy transfer or transformation, some energy is lost as unusable heat, increasing the entropy (disorder) of the system. This explains why energy transfer between trophic levels is inefficient.
Equilibrium is the tendency of a system to return to an original state following disturbance. There are different types of equilibrium:
Static equilibrium is a state where there is no change in the system over time. This is often a non-living example.
Dynamic equilibrium is a state of balance achieved through continuous, small-scale changes and adjustments. Most natural systems exist in a state of dynamic equilibrium.
Can involve negative feedback loops: tend to dampen down or counteract any deviation from an equilibrium, promoting stability. For example, if a population increases, resource availability decreases, leading to increased mortality and a return to a lower population size.
Can involve positive feedback loops: tend to amplify changes and drive the system away from its original equilibrium, leading to instability and potentially a new equilibrium. For example, rising temperatures can lead to the melting of ice, which reduces the Earth's reflectivity (albedo), leading to further warming.
Stable equilibrium: the system returns to its original equilibrium after a disturbance.
Unstable equilibrium: the system does not return to its original equilibrium; instead, it reaches a new equilibrium.
Resilience refers to the ability of a system to recover after a disturbance. A resilient system can withstand shocks and return to its original state. Factors that can affect the resilience of a system include its diversity and the complexity of its feedback mechanisms.
Tipping points (also known as thresholds) are points in a system beyond which a sudden and irreversible change to a new state occurs. Positive feedback loops can drive systems towards tipping points.
Topic 1.4: Sustainability
Knowledge and Understanding:
Sustainability: the use and management of resources that allows full natural replacement of the resources exploited and full recovery of the ecosystems affected by their extraction and use. It can also be defined as "meeting the needs of the present without compromising the ability of future generations to meet their own needs".
Natural capital: natural resources that can produce a sustainable natural income of goods or services. Examples include living resources, non-living resources, ecosystem support, timber, fisheries, and agricultural crops.
Natural income: the yield obtained from natural resources. For instance, the sustainable yield from a forest, fisheries, or water supply.
There is a relationship between natural capital, natural income, and sustainability: Sustainability requires that human use of natural capital does not exceed natural income, ensuring that resources remain available for future generations.
Ecosystems provide life-supporting services and goods that are essential for human well-being. These include timber, fisheries, and agricultural crops, as well as services like water purification, flood protection, and pollination.
Environmental Impact Assessments (EIAs): baseline studies undertaken before a development project is undertaken. They assess the environmental, social, and economic impacts of the project, predicting and evaluating possible impacts and suggesting mitigating strategies. EIAs help decision-makers consider the potential environmental consequences of projects and can guide more sustainable development.
Environmental indicators such as water pollution, air pollution, loss of biodiversity, soil degradation, and resource depletion can provide valuable information about the state of the environment and whether resource use is sustainable. Trends in these indicators can highlight areas where unsustainable practices are occurring.
Ecological footprint (EF): the area of land and water required to sustainably provide all the resources at the rate at which they are being consumed by a given population. Comparing a population's EF with the available biocapacity (the capacity of an area to provide resources and absorb wastes) can indicate whether consumption patterns are sustainable. If the EF exceeds biocapacity, it suggests unsustainable resource use.
The Millennium Development Goals (MDGs), established by the UN in 2000, aimed to address key global challenges by 2015. Evaluating the progress towards or achievement of these goals (or the subsequent Sustainable Development Goals (SDGs)) can provide insights into global efforts towards sustainability and highlight areas where more action is needed. The MDGs addressed issues like poverty, hunger, education, gender equality, child mortality, maternal health, HIV/AIDS, and environmental sustainability. The SDGs are a broader set of goals that succeeded the MDGs.
Topic 1.5: Humans and pollution
Knowledge and Understanding:
Pollutants are substances or agents released into the environment by human activities. These can include:
Matter (gases, liquids, or solids containing carbon atoms).
Energy (sound, light, heat).
Living organisms (invasive species or biological agents).
Primary pollutants are active on emission. Examples include pollutants active on emission such as carbon monoxide from the incomplete combustion of fossil fuels and sulfur dioxide from the burning of fossil fuels.
Secondary pollutants are formed by primary pollutants undergoing physical or chemical changes. An example includes sulfuric acid which is formed when sulfur trioxide reacts with water or nitrogen oxides react with water.
Point source pollution comes from a single, identifiable source (e.g., a factory pipe).
Non-point source pollution comes from diffuse sources (e.g., agricultural runoff).
Pollution can be classified by its persistence:
Biodegradable pollutants are broken down by natural processes.
Persistent pollutants are not easily broken down and can remain in the environment for a long time.
Pollution can also be classified by its effect:
Acute pollution involves a large release of pollutants causing immediate harm.
Chronic pollution involves the long-term release of smaller amounts of pollutants.
Major sources of pollution include the combustion of fossil fuels, domestic waste, industrial waste, and agricultural waste.
The combustion of fossil fuels releases various pollutants such as carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen oxides, photochemical smog (including tropospheric ozone, PANs, VOCs), and particulates. The effects of these pollutants include climate change, acid deposition, respiratory irritation, eye irritation, damage to plants, and problems associated with reduced visibility.
Domestic waste includes organic (food and sewage), paper waste, plastics (containers, packaging), tins, heavy metals, detergents, and radioactive materials. These can cause eutrophication, waterborne diseases, the spread of pathogens, bioaccumulation, and various health issues.
Industrial waste can contain heavy metals, acids, and heat, leading to poisoning, reduced solubility of gases in water, and thermal pollution.
Agricultural waste includes fertilizers (nitrates and phosphates), pesticides (herbicides and insecticides), animal waste, and organic waste, which can cause eutrophication, disease spread, and bioaccumulation.
Photochemical smog is formed by the reaction of nitrogen oxides and volatile organic compounds in the presence of sunlight.
Acid rain is primarily caused by sulfur dioxide and nitrogen oxides reacting with water in the atmosphere to form sulfuric and nitric acids.
Pollution Management Strategies (3 levels):
Altering human activity: This involves changing behaviors to reduce the production of pollutants. Examples include:
Education to encourage reduced consumption.
Developing and using alternative technologies.
Implementing stricter regulations and standards.
Introducing economic incentives or disincentives.
Controlling release of pollutant: This focuses on preventing pollutants from entering the environment. Examples include:
Treating wastewater before discharge.
Controlling emissions from industrial processes.
Developing cleaner technologies for extracting resources.
Managing agricultural runoff.
Cleaning up the pollutant and restoring ecosystems: This involves removing pollutants already in the environment. Examples include:
Removing plastic from the oceans.
Reforestation to help absorb air pollutants.
Remediating contaminated soil.
Restocking depleted fish populations.
Case Study: DDT and Malarial Mosquitoes:
DDT (dichlorodiphenyltrichloroethane) is an insecticide that was widely used to control malarial mosquitoes.
It was effective in reducing malaria transmission and saved millions of lives.
However, DDT is a persistent organic pollutant that is not easily biodegradable and can bioaccumulate in food chains, causing harm to non-target organisms, including humans.
The use of DDT exemplifies the conflict between the benefits of a pollutant (disease control) and its negative environmental and health impacts.
Due to its persistence and harmful effects, DDT has been banned or restricted in many countries.
TOPIC 2: ECOSYSTEMS AND ECOLOGY
Topic 2.1: Species and Populations
Knowledge and Understanding:
A species is a group of organisms sharing common characteristics that interbreed and produce fertile offspring.
A habitat is the environment in which a species normally lives.
A niche describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds.
The fundamental niche describes the full range of conditions and resources in which a species could survive and reproduce.
The realized niche describes the actual conditions and resources in which a species exists due to biotic interactions.
The non-living, physical factors that influence organisms are termed abiotic factors. Examples include temperature, sunlight, pH, salinity, and precipitation.
The interactions between the organisms (living components) are termed biotic factors. These include predation, herbivory, parasitism, mutualism, disease, and competition.
Interactions should be understood in terms of the influences each species has on the population dynamics of others and on the carrying capacity of the environment.
A population is a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.
Population density is the number of individuals in a stated area (e.g., per square kilometer).
Population size is the total number of individuals of a species present at a given time.
Three factors affect population size:
Mortality (death rate)
Natality (birth rate)
Migration (immigration and emigration)
Immigration is the moving into of an area.
Emigration is the moving out of an area.
An ecosystem has a carrying capacity that limits population growth.
Carrying capacity (K) is the maximum number of individuals of a species that the environment can sustainably support in a given area.
Limiting factors will slow population growth as it approaches the carrying capacity of the system.
Abiotic factors can act as limiting factors. Examples include how much space there is, availability of light, water, nutrients, and temperature.
Biotic factors can also act as limiting factors. Examples include competition for resources, predation, and the spread of disease.
No two species can have the same ecological niche in the same habitat at the same time; this is the competitive exclusion principle, and it often leads to one species either adapting its realized niche or being excluded by the other.
Population interactions such as competition, predation, parasitism, and mutualism influence the population size of each species involved.
Competition can be intraspecific (within a species) or interspecific (between different species).
Predation is where one organism (the predator) hunts and kills another (the prey).
Parasitism is where one organism (the parasite) lives on or in another (the host), obtaining food from it and potentially causing harm.
Mutualism is an interaction where both species benefit.
Population growth can be exponential or logistic.
Exponential growth (J-curve) occurs when there are unlimited resources, and the population increases at a constant rate.
Logistic growth (S-curve) occurs when population growth slows down as it approaches the carrying capacity, often due to limiting factors.
The maximum population size is limited by the carrying capacity (K) of the ecosystem.
Factors limiting population growth result in increased mortality or decreased natality, or both.
Topic 2.2 Communities and Ecosystems
Knowledge and Understanding:
A community is a group of populations living and interacting in a common habitat.
An ecosystem is a community of interdependent organisms and the physical environment they inhabit. An ecosystem is a community interacting with the physical environment.
In an ecosystem, there is a flow of energy and a cycling of nutrients.
Respiration and photosynthesis are processes with inputs, outputs, and transformations of energy and matter.
Photosynthesis is the conversion of light energy into chemical energy in autotrophs. The photosynthetic reaction is: carbon dioxide + water --(light energy)--> glucose + oxygen. Photosynthetic organisms produce the raw material for producing biomass.
Respiration is the conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy. The respiration reaction is: glucose + oxygen --> carbon dioxide + water + energy. During respiration, large amounts of energy are dissipated as heat.
Trophic levels are the positions that organisms occupy in a food chain.
Producers (autotrophs) are typically plants or algae that produce their own food using sunlight. Producers are the first trophic level in a food chain.
Consumers (heterotrophs) obtain energy by feeding on other organisms.
Primary consumers feed on producers (herbivores).
Secondary consumers feed on primary consumers (carnivores or omnivores).
Tertiary consumers feed on secondary consumers (carnivores or omnivores).
Decomposers (detritivores and saprotrophs) obtain energy from dead organic matter. Detritivores (e.g., maggots, woodlice) derive their energy from detritus. Saprotrophs (e.g., bacteria and fungi) obtain their energy and nutrients from dead organic matter by extracellular digestion and are vital for nutrient recycling.
Feeding relationships involve flows of energy and matter. A food chain shows the flow of energy from one trophic level to the next. A food web is a complex network of interconnected food chains, showing the feeding relationships within a community. Ecological pyramids show the relative amounts of energy or matter contained within each trophic level.
Pyramids of numbers represent the number of organisms at each trophic level.
Pyramids of biomass represent the total mass of living organisms at each trophic level. In some aquatic ecosystems, the biomass of producers (phytoplankton) may be lower than that of the consumers (zooplankton) due to the high turnover rate of phytoplankton.
Pyramids of productivity represent the rate of energy flow and production of biomass at each trophic level.
Energy transfer and transformations in ecosystems: The Sun's energy drives most ecosystems. Energy flows through ecosystems and is not recycled. There is a decrease in the amount of energy available at each successive trophic level. Only a fraction of the energy (around 10%) is transferred from one trophic level to the next; the rest is lost as heat or used for respiration. This limits the length of food chains.
Biomass is the total dry mass of living organisms in a given area or volume.
Nutrient cycles describe the movement of elements (e.g., carbon, nitrogen, phosphorus) through the biotic and abiotic components of an ecosystem. Nutrients are recycled within an ecosystem.
Pollutants can disrupt ecosystem processes. Persistent pollutants (e.g., DDT) accumulate in organisms at higher trophic levels, a process known as bioaccumulation. As consumers at each trophic level feed on many organisms from lower trophic levels, the concentration of these pollutants becomes magnified at higher levels in the food chain. This increase in concentration at successive trophic levels is called biomagnification. Non-biodegradable pollutants remain in the environment for long periods and can have long-term impacts on ecosystems.
Topic 2.3: Flows of Energy and Matter
Knowledge and Understanding:
Solar radiation is the initial source of energy for almost all ecosystems. Only a small fraction of the incoming solar energy is captured by producers (plants and algae) through photosynthesis.
Energy flows through ecosystems in a unidirectional manner.
The conversion of energy into biomass for a given period is productivity.
Gross Primary Productivity (GPP) is the total energy captured by producers.
Net Primary Productivity (NPP) is the energy remaining after producers have accounted for their respiration (NPP = GPP - R). This is the energy available to consumers.
NPP can be calculated by subtracting respiratory losses (R) from GPP (NPP = GPP - R).
Feeding relationships involve the transfer of energy and matter from one trophic level to the next.
Gross Secondary Productivity (GSP) is the total energy assimilated by consumers.
Net Secondary Productivity (NSP) is the energy remaining in consumers after respiratory losses (NSP = GSP - R).
Biomass is the total mass of living organisms.
Ecological efficiency (trophic efficiency) is the percentage of energy assimilated by an organism in a trophic level that is transferred to the next trophic level. This is typically low, around 10%, because most energy is lost as heat through respiration, excretion, or is not consumed.
Matter flows and is transformed within ecosystems.
Nutrient cycles describe the movement of elements through the biotic and abiotic components of an ecosystem. Key nutrient cycles include:
The Carbon Cycle: Carbon is exchanged between the atmosphere, oceans, and living organisms through processes like photosynthesis, respiration, combustion, and decomposition. Human activities like burning fossil fuels and deforestation have significantly increased atmospheric carbon dioxide.
The Nitrogen Cycle: Nitrogen is essential for building proteins and nucleic acids. Atmospheric nitrogen (N₂) is converted into usable forms by nitrogen-fixing bacteria, lightning, and industrial processes (Haber-Bosch process). These forms are then assimilated by plants, passed on to consumers, and returned to the soil and atmosphere through decomposition and denitrification. Human impacts include the use of nitrogen fertilizers, which can lead to eutrophication, and the release of nitrogen oxides through combustion.
Other key cycles include the water cycle and the phosphorus cycle.
Storages in nutrient cycles include organisms, soil, fossil fuels, and the atmosphere.
Flows in nutrient cycles include consumption, assimilation, decomposition, and processes like photosynthesis, respiration, nitrogen fixation, nitrification, denitrification, combustion, and precipitation.
Human activities significantly impact energy flows and nutrient cycles. Deforestation reduces primary productivity and alters water cycles. Burning fossil fuels releases large amounts of carbon dioxide, contributing to climate change. The use of fertilizers can disrupt nutrient balances and lead to pollution. Agricultural practices can impact soil health and nutrient cycling. Pollution can contaminate water and disrupt aquatic ecosystems.
Maximum sustainable yields are relevant to human harvesting of natural resources and are influenced by energy flow and productivity. The highest rates of productivity are often found in the earlier stages of succession.
Topic 2.4: Biomes, Zonation and Succession
Knowledge and Understanding:
Biomes are collections of ecosystems sharing similar climatic conditions which can be grouped into five major classes: aquatic, forest, grassland, desert and tundra. Each of these classes has characteristic limiting factors, productivity and biodiversity.
The tri-cellular model of atmospheric circulation explains the distribution of precipitation and temperature influencing the location of biomes.
Zonation is evident in many habitats. As one moves along an environmental gradient, different communities are found. Examples include changes in vegetation with altitude, the distribution of species along a rocky shore based on tidal inundation, and changes in species composition as you move away from a shoreline into deeper water.
Succession is the orderly process of change over time in a community.
During succession, there is a predictable change in species composition.
Early stages (pioneer communities) are characterized by species that can tolerate harsh conditions (r-selected species).
Later stages (climax communities) are characterized by more complex and stable communities with K-selected species.
Primary succession occurs on newly exposed or formed land where no soil exists (e.g., volcanic rock).
Secondary succession occurs in areas where a community has been removed or disturbed, but soil remains (e.g., after a fire or deforestation).
During succession, the following general patterns of change occur:
Gross primary productivity (GPP) and net primary productivity (NPP) tend to increase in the early stages as vegetation establishes.
Respiration increases as biomass accumulates.
The ratio of productivity to respiration (P:R) changes over time, typically moving towards a ratio of 1 in a climax community.
Biodiversity generally increases during succession, reaching a peak in intermediate stages before potentially decreasing slightly in a climax community.
Biomass increases over succession.
Soil depth and organic matter content increase.
Nutrient cycling becomes more complex and efficient.
Climax communities are not always stable and can be influenced by factors such as climate, disturbance, and species interactions, potentially leading to alternative stable states. For example, grazing pressure can maintain a grassland ecosystem and prevent it from succeeding to a forest.
Human activities can significantly impact succession, often deflecting it or preventing the establishment of climax communities. Activities like deforestation, agriculture, and pollution can simplify ecosystems and reduce biodiversity.
r-selected species are adapted for rapid growth and reproduction in unstable environments (e.g., pioneer species). They typically have short lifespans, high reproductive rates, and provide little parental care.
K-selected species are adapted for stable environments and are competitive in resource-limited conditions (e.g., climax community species). They typically have longer lifespans, lower reproductive rates, and invest more in parental care.
Topic 2.5: Investigating Ecosystems — Practical Work
Knowledge and Understanding:
The study of an ecosystem requires methods to measure and analyse its biotic and abiotic components. This can include the identification of species using keys.
Sampling strategies are used to estimate population size and distribution of organisms.
Methods for measuring abiotic factors include temperature, light intensity, wind speed, soil texture, slope, soil moisture, drainage, and mineral content. For aquatic ecosystems, additional factors like salinity, turbidity, flow velocity, pH, temperature, and dissolved oxygen are important.
Methods for measuring biotic factors include:
Quadrats are used for sampling non-motile or slow-moving organisms to determine population density, percentage cover, and frequency. The size and number of quadrats should be appropriate for the organisms and habitat being studied.
Transects are used to examine changes in species distribution along an environmental gradient. Line transects (recording species at intervals along a line) and belt transects (sampling within a defined width along a line) are common methods.
Methods for estimating the abundance of motile organisms include capture-mark-recapture techniques.
Biomass can be estimated by collecting samples, drying them to a constant mass, and weighing them. This process is destructive.
Productivity is the rate of biomass production. Measuring productivity can be complex and varies depending on the ecosystem and trophic level. For aquatic ecosystems, measuring changes in dissolved oxygen in light and dark bottles can provide estimates of primary productivity. For terrestrial ecosystems, changes in plant biomass over time can be measured.
Species diversity can be assessed using indices such as the Simpson diversity index. This index takes into account both the number of species present (richness) and their relative abundance (evenness).
Ecological investigations should consider ethical implications and aim to minimize disturbance to the environment. The validity of data is influenced by factors such as sample size, random sampling, and the accuracy of measurement techniques. Improvements to investigations can include increasing sample size, refining sampling methods, and using more precise measuring instruments.
TOPIC 3: BIODIVERSITY AND CONSERVATION
Topic 3.1: An Introduction to Biodiversity
Knowledge and Understanding:
Biodiversity is a broad concept including species diversity (the number of species and their relative proportions), genetic diversity (the range of genetic material present in a population or species), and habitat diversity (the range of different habitats in an ecosystem or biome).
Species diversity in communities is a product of two variables: the number of species (richness) and their relative proportions (evenness).
Communities can be described and compared by the use of diversity indices.
Habitat diversity refers to the range of different habitats in an ecosystem or biome.
Genetic diversity refers to the range of genetic material present in a population or species.
The quantification of biodiversity is important to conservation by allowing the identification of areas of high biodiversity, the monitoring of changes over time, and the assessment of the effectiveness of conservation efforts. Providing numerical values allows for comparisons between different areas and the setting of conservation priorities.
The relative values of biodiversity can be considered from different perspectives, including intrinsic value, ecological value (e.g., ecosystem stability, provision of resources), economic value (e.g., tourism, medicines), and aesthetic value.
A biodiversity hotspot is a region with a high level of endemic species that has experienced significant habitat loss. These are areas with exceptionally high species richness that are under threat.
A megadiversity country is one that harbors a very high percentage of the Earth's species.
There are threats to biodiversity at various levels, including:
Natural hazards: These can cause habitat destruction and species loss.
Human activity: These are often more significant and include habitat destruction, fragmentation, overexploitation, pollution, introduction of invasive species, and climate change.
Increased human population and consumption patterns exacerbate these threats.
The rate of current species loss is significantly higher than background extinction rates.
Topic 3.2: Origins of Biodiversity
Knowledge and Understanding:
The total number of species on Earth is estimated to be vast, but only a fraction has been described and recorded. Mathematical models are used to estimate species numbers, but these are often crude and subject to revision.
The current rate of species loss is greater than the background extinction rate and is largely due to human activities.
Speciation, the formation of new species, can occur when populations are isolated geographically or reproductively, preventing gene flow. Isolation can lead to different selection pressures and the gradual accumulation of genetic differences, eventually resulting in the inability to interbreed.
Plate tectonics and continental drift have significantly influenced biodiversity over millions of years. The movement of continents has led to:
Isolation of land masses, promoting endemic speciation.
Changes in climate and sea levels, which can drive extinction events and create new opportunities for speciation.
Formation of new habitats through geological processes like mountain building.
Natural selection is a key mechanism of evolution. Individuals with traits that are advantageous in a particular environment are more likely to survive and reproduce, passing on those favorable traits to their offspring. Over time, this process can lead to the evolution of new species adapted to their specific environments.
The Earth's history has been marked by several periods of mass extinction, where a large percentage of species died out in a relatively short period. Possible causes of mass extinctions include:
Tectonic plate movements.
Volcanic eruptions.
Climate change (e.g., rapid cooling or warming).
Asteroid impacts.
Following a mass extinction, there is often a period of adaptive radiation, where surviving species diversify and fill the ecological niches left vacant by the extinct species.
The rates of speciation and extinction vary and are influenced by a variety of factors, including environmental stability, competition, and the availability of resources.
Humans are causing a significant increase in the rate of extinction through habitat destruction, overexploitation, pollution, climate change, and the introduction of invasive species. This anthropogenic extinction event is unprecedented in its speed and scale and poses a major threat to global biodiversity.
Topic 3.3: Threats to Biodiversity
Knowledge and Understanding:
Estimates of the total number of species vary considerably due to mathematical models being limited by available data and lack of finance for scientific research, resulting in many groups being under-recorded.
The current rate of species loss appears to be far greater than in the recent past, due to increased human influence; human activities are causing species extinctions.
The International Union for Conservation of Nature (IUCN) publishes the Red List of Threatened Species, which assesses the conservation status of species in terms of extinction risk. Factors considered include population size, degree of specialization, distribution, reproductive potential and behaviour, geographic range and degree of fragmentation, habitat quality, trophic level, and others.
Tropical biomes contain some of the most globally biodiverse areas and their unsustainable exploitation results in massive losses of habitats and consequently, biodiversity. Most tropical countries are less economically developed (LEDCs) and therefore there is conflict between exploitation, sustainable development and conservation.
Most losses in biodiversity are due to human activities, including:
Habitat destruction: This includes deforestation, urbanization, and agricultural expansion, directly destroying the places where species live.
Habitat fragmentation: Breaking large habitats into smaller, isolated patches can reduce population sizes and genetic diversity.
Overexploitation: Harvesting species at a rate that exceeds their ability to reproduce can lead to population collapse and extinction (e.g., overfishing, hunting).
Pollution: Contamination of air, water, and soil can harm or kill organisms and degrade habitats. Different types of pollution include chemical pollution, eutrophication, and thermal pollution.
Introduction of invasive species: Non-native species can outcompete native species for resources, prey on them, introduce diseases, or alter habitats, leading to declines and extinctions of native populations.
Spread of disease: Human activities can facilitate the spread of diseases to wild populations.
Climate change: Changes in temperature, precipitation patterns, and sea levels can alter habitats and species distributions, potentially leading to extinctions if species cannot adapt or migrate quickly enough.
Certain species are more vulnerable to extinction than others due to factors such as:
Narrow geographical range: Species confined to a small area are more susceptible to localized threats.
Small population size or declining numbers: Smaller populations have less genetic diversity and are more vulnerable to random events.
Low reproductive potential: Species that reproduce slowly take longer to recover from population declines.
Specialized niche: Species highly dependent on specific resources or conditions are vulnerable if those are threatened.
Low genetic diversity: Lack of genetic variation reduces a species' ability to adapt to environmental changes or resist diseases.
Large body size: Larger animals often have lower reproductive rates and require more resources, making them more vulnerable to overexploitation and habitat loss.
High trophic level: Top predators often have smaller population sizes and rely on lower trophic levels, making them susceptible to disruptions in the food web.
Fixed migration routes: Species with specific migration routes are vulnerable if any part of that route is disrupted.
Late successional species: These species are adapted to stable, mature habitats and may not be able to colonize new areas quickly.
The conflict surrounding tropical rainforests often involves the economic needs of local populations and national development (e.g., logging for timber, agriculture, mining) versus the ecological importance of these biomes in terms of biodiversity, carbon sequestration, and climate regulation. Sustainable development aims to balance these competing interests, but effective implementation can be challenging. Conservation efforts seek to protect rainforests and their biodiversity through measures like establishing protected areas, promoting sustainable resource use, and supporting conservation initiatives.
Human activities have a significant negative impact on the biodiversity of tropical biomes. Deforestation for agriculture (including cattle ranching and palm oil plantations) and logging are major drivers of habitat loss. Mining, road construction, and urbanization also contribute to habitat destruction and fragmentation. Overhunting and the illegal wildlife trade further threaten many species in these regions. Climate change is also projected to have severe impacts on tropical rainforests, potentially leading to changes in species distributions and increased extinction rates.
Topic 3.4: Conservation of Biodiversity
Applications and Skills:
Discuss the arguments for preserving species and habitats. These can include:
Economic reasons: Biodiversity provides resources like food, medicine, and tourism opportunities.
Ecological reasons: Healthy ecosystems provide essential services such as pollination, water purification, and climate regulation.
Ethical/Intrinsic value: Many believe species have a right to exist regardless of their usefulness to humans.
Aesthetic reasons: Nature and biodiversity are sources of beauty and inspiration.
Recreational reasons: Many people enjoy spending time in nature and observing wildlife.
Scientific and educational value: Biodiversity provides opportunities for research and learning.
Human health: Biodiversity can play a role in disease regulation and provides medicinal resources.
Evaluate the relative strengths and weaknesses of in situ (terrestrial and aquatic) and ex situ conservation strategies.
In situ conservation involves protecting species within their natural habitat.
Strengths: Maintains ecological interactions, conserves the entire ecosystem, and is often more cost-effective in the long term.
Weaknesses: Can be difficult to manage and protect large areas effectively, populations may continue to decline due to external factors, and may face conflicts with human land use.
Ex situ conservation involves removing species from their natural habitat for protection. Examples include zoos, botanical gardens, seed banks, and captive breeding programs.
Strengths: Provides a safe environment, allows for intensive management and breeding programs, can be used for education and research.
Weaknesses: Can be expensive, may not be possible for all species, can lead to loss of genetic diversity and adaptation to the wild, and reintroduction can be difficult.
Discuss the role of international conventions in promoting conservation. Examples include:
CITES (Convention on International Trade in Endangered Species): Regulates international trade in endangered species.
CBD (Convention on Biological Diversity): Aims to conserve biological diversity, promote its sustainable use, and ensure the fair and equitable sharing of benefits arising from the utilization of genetic resources.
Ramsar Convention on Wetlands: Provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources.
World Heritage Convention: Aims to protect natural and cultural sites of outstanding universal value.
Knowledge and Understanding:
Arguments for preserving species and habitats can be based on ethical, aesthetic, genetic resource and commercial considerations, and their role in life support systems.
International, governmental and non-governmental organizations (NGOs) are involved in conservation and restoration of ecosystems and biodiversity, with varying levels of effectiveness due to their different scales of operation, funding and political influence.
International organizations like the IUCN, UNEP, and WWF operate globally, set agendas, and influence policy.
Governmental organizations at national and local levels establish and enforce environmental regulations, manage protected areas, and implement conservation programs.
Non-governmental organizations (NGOs) such as Greenpeace and local conservation groups often focus on specific issues or regions, raise public awareness, and advocate for policy changes. Their effectiveness can vary based on funding, membership, and political influence.
A range of conservation approaches exist, including:
Habitat conservation: Protecting and managing natural habitats is crucial for maintaining biodiversity. This can involve establishing protected areas like national parks and reserves. Factors influencing the success of protected areas include size, shape, edge effects, corridors, and management effectiveness.
Species-based conservation: Focusing on specific endangered species through measures like captive breeding, habitat restoration, and anti-poaching efforts. The IUCN Red List provides a classification system for the conservation status of species.
Legislation and enforcement: Implementing and enforcing laws to protect species and habitats, regulate trade, and control pollution.
Education and awareness: Raising public awareness about the importance of biodiversity and conservation through education programs and campaigns.
Sustainable development: Integrating conservation with economic development to ensure that human activities do not compromise biodiversity in the long term.
Restoration ecology: Attempting to restore degraded ecosystems to their former state.
Ex situ conservation measures: As mentioned above, these include zoos, botanical gardens, and seed banks.
The effectiveness of conservation efforts can be limited by factors such as funding, political will, human population pressure, and the complexity of ecological systems. Conflicts can arise between conservation goals and the needs and desires of local populations and economic development.
TOPIC 4: WATER, FOOD PRODUCTION SYSTEMS AND SOCIETY
Topic 4.1: Introduction to Water Systems
Knowledge and Understanding:
Solar radiation drives the hydrological cycle by causing evaporation.
Global water distribution includes major stores such as oceans (about 97% of the Earth's water), ice caps and glaciers (about 68.7% of freshwater), and groundwater (about 30.1% of freshwater). Surface water (lakes, rivers, swamps) and atmospheric water make up a very small percentage.
Flows in the hydrological cycle include precipitation, interception, surface run-off, infiltration, percolation, and stream-flow or currents. Also, evaporation and transpiration transfer water to the atmosphere, and condensation leads to precipitation.
Storages in the hydrological cycle include oceans, groundwater, atmosphere, ice caps and glaciers, lakes, rivers, soil, and organisms.
Human activities can interfere with the hydrological cycle in various ways.
Withdrawals for domestic use, irrigation, and industry reduce water in sources.
Discharges of pollutants alter water quality.
Changing the speed of water flow through urbanization and channeling rivers impacts drainage.
Diverting rivers and creating dams alter water distribution and storage.
Deforestation decreases interception and transpiration, increasing surface run-off and erosion.
Urbanization and road construction increase impermeable surfaces, leading to increased run-off and decreased infiltration.
Ocean circulation systems are driven by temperature and salinity gradients and influence the distribution of energy and water globally. Surface currents (upper 400 m) are moved by wind, while deep currents are affected by density differences (thermohaline circulation). These currents redistribute heat, impacting global climate.
Topic 4.2: Access to Freshwater
Knowledge and Understanding:
Access to adequate freshwater is a critical issue. Key facts from the World Water Council include:
Around 2.6 billion people lack clean drinking water.
Approximately 1.8 billion people die annually from diarrheal diseases.
3,900 children die each day from waterborne diseases.
3,000 gallons of water are embedded in the daily food of one person in a developed country.
250 rivers cross international boundaries.
Over 260 major basins are shared by two or more countries.
Quantity of water needed to produce 1 kg of: wheat - 1,000 l; rice - 3,500 l; beef - 15,000 l.
Water supplies can be enhanced through various methods:
Reservoirs.
Redistribution (e.g., through canals and pipelines).
Desalination.
Artificial recharge of aquifers.
Water conservation (including reducing domestic, agricultural, and industrial use).
Recycling (including grey water systems).
Sustainable use of freshwater resources is essential for full ecological recovery and the ability of natural systems to provide services.
Water resources can be enhanced through management, including:
Reducing demands through conservation strategies.
Improving water use efficiency in agriculture, industry, and domestic settings.
Protecting water resources from pollution and overuse.
The scarcity of water resources can lead to conflict at local, national, and international levels. The Aral Sea shrinking is presented as a case study of unsustainable water use, leading to ecological and human consequences.
Factors affecting access to freshwater include:
Climate change, which can disrupt rainfall patterns and further affect water availability.
Population increases, leading to increased demand for water.
Irrigation and industrialization, which significantly increase water demand.
Pollution and contamination, which can reduce the availability of usable freshwater.
Contamination through sewage, fertilizers and pesticides, industrial discharge, and the accumulation of persistent pollutants.
The Millennium Development Goals (MDGs) aimed to reduce by half the proportion of people without sustainable access to safe drinking water and basic sanitation.
Natural capital related to water is defined as the stock of freshwater and supporting ecosystems that provide a flow of beneficial goods and services. This includes rivers, wetlands, and underground aquifers.
Sustainable water management involves using water in a way that meets current needs without compromising the ability of future generations to meet their own needs.
An aquifer is an underground layer of permeable rock or sediment that holds groundwater. They are replenished by infiltration of precipitation.
Water pollution is a major issue that reduces the availability of clean freshwater. Types of pollutants include organic wastes, inorganic nutrients, toxic metals, synthetic organic chemicals, suspended solids, hot water, oil, radioactive pollution, pathogens, light, noise and biological (invasive) species.
Biodegradation of organic material utilizes oxygen in the water, reducing the dissolved oxygen available for other aquatic life, potentially leading to biochemical oxygen demand (BOD).
Eutrophication can occur when lakes and coastal waters receive inputs of nutrients (nitrates and phosphates), leading to an excess growth of algae and phytoplankton. This can eventually lead to oxygen depletion and dead zones.
Acid deposition indirectly results in pollution by affecting soils and waters, which in turn affects species.
Application of water pollution management strategies includes reducing human activities that produce pollutants, reducing the release of pollution into the environment, and removing pollutants from the environment.
Strategies for reducing pollution include altering human activity, regulating and reducing pollutants at the point of emission, and clean-up and restoration of polluted waters.
Water scarcity can be physical (not enough water to meet demands) or economic (lack of infrastructure to supply water).
Topic 4.3: Aquatic Food Production Systems
Knowledge and Understanding:
Wild fisheries are naturally occurring populations of fish and other aquatic life that are harvested for food.
Aquaculture is the farming of aquatic organisms such as fish, crustaceans, molluscs, and aquatic plants.
Aquatic food production systems can be divided into wild fisheries and aquaculture.
Wild fisheries face several challenges, including overfishing, habitat destruction, pollution, and climate change.
Aquaculture has grown significantly in recent decades and now accounts for a substantial portion of global seafood production.
Different types of aquaculture systems exist, including ponds, cages, and tanks, and they can vary in their environmental impacts.
Environmental impacts of aquaculture can include:
Habitat destruction (e.g., mangrove removal for shrimp farms).
Pollution from fish waste, uneaten feed, and chemicals.
Disease transfer to wild populations.
Escape of farmed fish, which can compete with or breed with wild populations.
Use of wild-caught fish as feed for farmed fish.
Strategies to increase the sustainability of aquatic food production include:
Implementing and enforcing stricter fishing regulations.
Protecting and restoring critical habitats.
Reducing pollution from land-based sources.
Developing more sustainable aquaculture practices (e.g., closed-loop systems, use of alternative feeds).
Promoting responsible consumer choices.
Conflicts can arise between different users of the marine environment, such as fishing industries, aquaculture operations, tourism, and conservation efforts.
Sustainable aquaculture aims to minimize environmental and social impacts while meeting the growing demand for seafood. This involves careful site selection, waste management, disease control, and responsible sourcing of feed.
Topic 4.4: Water Pollution
Knowledge and Understanding:
Water pollution is defined as the contamination of water sources by substances that make the water unusable for drinking, cooking, cleaning, swimming, and other activities. Pollution of water, both groundwater and surface water, is a major global environmental problem.
There is a wide range of freshwater and marine pollution sources.
Types of aquatic pollutants include:
Organic pollutants: These include organic wastes (sewage, food processing), which can lead to biochemical oxygen demand (BOD) as they decompose, reducing dissolved oxygen for aquatic life. They also include synthetic organic chemicals like pesticides and industrial chemicals.
Inorganic pollutants: These consist of inorganic nutrients (nitrates and phosphates from fertilizers and sewage) which can cause eutrophication. Other inorganic pollutants include toxic metals (mercury, lead) and acids from industrial processes and acid deposition.
Physical pollutants: These include suspended solids (silt, sediment), hot water from industrial cooling processes which reduces dissolved oxygen, oil spills, radioactive substances, noise pollution, light pollution, and biological pollutants such as invasive species and pathogens.
A biotic index indirectly measures pollution by assessing the impact on species in the community according to their tolerance and relative abundance. The presence or absence of certain invertebrate species can indicate the level of pollution.
Eutrophication is the enrichment of lakes and coastal waters with nutrients (nitrates and phosphates), leading to excessive algal growth (algal blooms). This can result in:
Oxygen-deficient (anaerobic) water when the algae die and decompose, leading to increased BOD.
Loss of biodiversity as fish and other aerobic organisms die due to lack of oxygen.
Death of higher plants due to reduced light penetration.
Increases in turbidity (cloudiness of water).
The formation of dead zones in oceans and lakes where oxygen levels are too low to support most marine life.
Some algal blooms can release toxins harmful to humans and animals.
Sources of eutrophication include fertilizers, detergents (phosphates), sewage, and intensive livestock rearing units.
Strategies for reducing pollution can be implemented at different stages:
Altering human activity: This involves reducing the production of pollutants, such as using less fertilizer or switching to phosphate-free detergents.
Regulating and reducing pollutants at the point of emission: This includes treating wastewater to remove pollutants before discharge, setting emission standards for industries, and controlling agricultural run-off.
Clean-up and restoration of polluted waters: This involves removing pollutants from the environment, such as dredging contaminated sediments, aeration of oxygen-depleted water, and restoring ecosystems.
Strategies for reducing eutrophication include limiting the use of fertilizers and detergents containing phosphates, treating wastewater to remove nitrates and phosphates, diverting or reducing run-off from agricultural land, and using buffer zones.
The impact of pollution can vary depending on the type of pollutant, its concentration, and the sensitivity of the ecosystem.
Dead zones in oceans and lakes are a significant consequence of water pollution and eutrophication. The Gulf of Mexico is mentioned as an example of a dead zone resulting from toxins and oxygen depletion caused by excess nitrates and phosphates from the Mississippi River.
Red tides in coastal waters, often caused by eutrophication leading to blooms of dinoflagellates, can produce toxins that harm marine life and humans.
Effective management requires a combination of strategies targeting the sources, pathways, and impacts of pollutants.
TOPIC 5: SOIL SYSTEMS AND SOCIETY
Topic 5.1: Introduction to soil systems
The soil system is a dynamic ecosystem with inputs, outputs, storages, and flows.
Inputs include organic material (leaf litter, parent material), precipitation, and energy.
Storages include organic matter, organisms, nutrients, minerals, air, and water.
Transfers within the soil involve biological mixing and leaching.
Transformations include decomposition, weathering, and nutrient cycling.
Outputs include uptake by plants and soil erosion.
The quality of soil influences the primary productivity of an area.
Soil is formed from the breakdown of rocks (minerals) and the decomposition of organic matter.
The structure and properties of sand, clay, and loam soils differ due to their particle size and arrangement.
Sand has large particles, leading to good drainage and aeration but poor water and nutrient retention.
Clay has small particles, resulting in poor drainage and aeration but good water and nutrient retention.
Loam, a mixture of sand, silt, and clay, provides a balance of drainage, aeration, water retention, and nutrient holding capacity, making it generally fertile.
Soil texture can be classified using a soil texture triangle, which shows the percentage composition of sand, silt, and clay.
Soil profiles are vertical cross-sections showing horizons (layers) with different characteristics due to weathering, decomposition, and leaching. Examples include the litter layer, topsoil (humus-rich A horizon), subsoil, parent material, and bedrock.
The humus layer (topsoil) is rich in organic matter and is crucial for plant growth.
Different soil horizons vary in their content of organic matter, minerals, air, and water, affecting their fertility.
Topic 5.2: Terrestrial Food Production Systems and Food Choices
Knowledge and Understanding:
Terrestrial food production systems are diverse and include farming of plants and animals for human consumption. These systems are influenced by a range of biotic and abiotic factors.
Energy flow in food production systems typically follows the principles of ecosystems, with energy entering through photosynthesis and being transferred through trophic levels. However, human intervention in agriculture often simplifies food webs and can alter energy pathways.
Nutrient cycling in food production systems can be significantly modified by human activities. For example, fertilizers add nutrients to the soil, while harvesting removes them. Sustainable systems aim to minimize nutrient loss and recycle nutrients effectively.
Different terrestrial farming systems have distinct characteristics and environmental impacts:
Commercial farming: Often characterized by large-scale production, monoculture, and the use of machinery, fertilizers, and pesticides. It aims for profit maximization.
Subsistence farming: Focuses on producing enough food to meet the needs of the farmer and their family, often using traditional methods and diverse crops.
Intensive farming: Aims to maximize yield per unit area through high inputs of labor, capital, and resources.
Extensive farming: Uses larger areas of land with lower inputs per unit area.
Arable farming: Focuses on growing crops.
Pastoral farming: Focuses on raising animals.
Mixed farming: Involves both crop and animal production.
The environmental impacts of terrestrial farming systems can include:
Habitat loss and fragmentation due to land conversion.
Soil degradation through erosion, nutrient depletion, and compaction.
Water pollution from fertilizers, pesticides, and animal waste.
Air pollution from machinery and livestock emissions.
Loss of biodiversity due to monoculture and habitat destruction.
Greenhouse gas emissions contributing to climate change.
The sustainability of food production systems can be evaluated by considering factors such as:
Resource use efficiency (water, energy, nutrients).
Impacts on soil health and biodiversity.
Levels of pollution and waste.
Social and economic equity.
Resilience to environmental change.
Food choices at the consumer level have significant consequences for the environment and human health. Factors influencing food choices include:
Cultural and religious beliefs.
Economic factors (cost, availability).
Ethical considerations (animal welfare, environmental concerns).
Health concerns and nutritional value.
Personal preferences and taste.
The environmental impacts of different food choices vary considerably. For example:
Meat production generally has a higher environmental footprint than plant-based foods in terms of land use, water use, and greenhouse gas emissions.
Locally sourced and seasonal foods can reduce transportation emissions and support local economies.
Organic farming practices can minimize the use of synthetic pesticides and fertilizers.
Food waste contributes significantly to environmental problems and inefficient resource use.
There are links between food production and food choices. Consumer demand can influence what and how food is produced. Promoting more sustainable food choices can drive changes in food production systems.
Strategies for more sustainable terrestrial food production include:
Improving agricultural practices (e.g., crop rotation, conservation tillage, integrated pest management).
Reducing food waste at all stages of the food system.
Shifting towards more plant-based diets.
Supporting sustainable and local food systems.
Implementing policies and regulations to promote sustainable agriculture.
Topic 5.3: Soil Degradation and Conservation
Knowledge and Understanding:
Soil degradation is a major environmental problem that can result from various human activities.
Soil erosion, the removal of topsoil by wind or water, is a significant form of soil degradation. It can be accelerated by activities like deforestation, overgrazing, and unsustainable farming practices.
Contamination of soil can occur through the introduction of pollutants such as heavy metals, pesticides, and industrial waste, reducing its fertility and potentially harming ecosystems and human health.
Salinization, the accumulation of salts in the soil, can happen in arid and semi-arid regions due to irrigation practices that lead to evaporation and salt buildup, hindering plant growth.
Desertification is the process by which fertile land becomes desert, typically due to a combination of climate change and unsustainable land management practices, including overgrazing and deforestation.
The relationship between soil ecosystem succession and soil degradation is that healthy, mature soils developed through succession are more resistant to degradation. Disturbances that interrupt succession or remove vegetation cover can leave the soil vulnerable to erosion and other forms of degradation.
Soil conservation measures aim to protect and improve soil quality. These include:
Windbreaks: Planting trees or shrubs to reduce wind speed and prevent wind erosion.
Terracing: Creating step-like platforms on sloping land to reduce water runoff and erosion.
Contour plowing: Plowing and planting crops along the natural contours of the land to slow water flow and reduce erosion.
Cover crops: Planting temporary vegetation between main crops to protect the soil from erosion and improve soil health.
Crop rotation: Planting different crops in a sequence to improve soil fertility, reduce pest and disease buildup, and minimize nutrient depletion.
Other measures mentioned include afforestation (planting trees) and avoiding overgrazing.
Sustainable soil management is crucial for maintaining food security, biodiversity, and ecosystem services.
TOPIC 6: ATMOSPHERIC SYSTEMS AND SOCIETY
Topic 6.1: Introduction to the Atmosphere
Knowledge and Understanding:
The atmosphere is a dynamic system with inputs, outputs, flows, and storages, and has undergone significant changes throughout geological time.
The atmosphere is predominantly a mixture of nitrogen and oxygen, with smaller amounts of carbon dioxide, argon, water vapour, and other trace gases. Figure 6.1 shows the approximate atmospheric composition near the surface as approximately 78% Nitrogen and 21% Oxygen.
Human activities impact the atmospheric composition through the release of pollutants such as carbon gases, ozone-depleting substances, oxides of nitrogen and sulfur, and particulates.
The atmosphere has a layered structure:
The troposphere (0-10 km above Earth) is where most clouds form.
The stratosphere (10-50 km) contains the ozone layer.
The mesosphere (50-80 km).
The thermosphere (80 km and higher). Figure 6.1 illustrates this vertical structure.
Most clouds form in the troposphere and play an important role in the albedo effect.
The greenhouse effect is a natural and necessary phenomenon maintaining suitable temperatures for living systems.
Short-wavelength radiation from the Sun passes through the atmosphere and heats the Earth's surface.
The Earth's surface then radiates longer-wavelength (infrared) radiation.
Greenhouse gases (such as carbon dioxide, water vapour, and methane) in the atmosphere absorb much of this infrared radiation and re-emit it in all directions, including back towards the Earth, thus warming the planet.
The albedo effect refers to the ability of a surface to reflect solar radiation. Light-colored surfaces (like ice and clouds) have a high albedo and reflect more radiation, while dark-colored surfaces (like forests and oceans) have a low albedo and absorb more radiation.
Changes in cloud cover and ice cover can significantly affect the Earth's overall albedo and thus its temperature.
Topic 6.2: Stratospheric Ozone
Knowledge and Understanding:
Stratospheric ozone (O₃) absorbs significant amounts of ultraviolet (UV) radiation from the Sun, especially harmful UV-B and UV-C. Increased UV radiation reaching the Earth's surface due to ozone depletion can lead to genetic mutations, health problems like skin cancer and cataracts, damage to immune systems, and harm to ecosystems.
The dynamic equilibrium of ozone formation in the stratosphere involves the breakdown of oxygen molecules (O₂) by UV radiation and the formation of ozone, as well as the breakdown of ozone by UV radiation.
Ozone-depleting substances (ODSs) released by human activities act as catalysts in the destruction of stratospheric ozone, disrupting this equilibrium. Key ODSs mentioned include:
Chlorofluorocarbons (CFCs) used in aerosols, refrigerants, and foam production.
Halons used in fire extinguishers.
Methyl bromide used as a pesticide.
Nitrogen oxides (NOx) emitted by high-flying aircraft.
The United Nations Environment Programme (UNEP) plays a significant role in international efforts to protect the ozone layer. UNEP facilitates international agreements and assesses the science of ozone depletion.
The Montreal Protocol on Substances that Deplete the Ozone Layer (1987) is a landmark international agreement aimed at phasing out the production and consumption of ODSs. It has been highly successful due to its legally binding nature, specific targets and timetables, and amendments to include more substances and accelerate phase-out schedules.
Despite the success of the Montreal Protocol, an illegal market for ODSs has emerged. This illegal trade undermines the goals of the Protocol and can delay ozone layer recovery. Factors contributing to the illegal market include the continued demand for CFCs in some applications and the potential for high profits.
Pollution management strategies to reduce ozone depletion, driven by the Montreal Protocol and implemented through national regulations, include:
Banning or phasing out the production and consumption of ODSs.
Developing and using alternatives to ODSs, such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). Note that while HCFCs are transitional substances with lower ozone-depleting potential, some HFCs are potent greenhouse gases, presenting a new environmental concern.
Recycling and safely disposing of ODSs in existing equipment.
International cooperation and enforcement to combat the illegal trade of ODSs.
The ozone layer is showing signs of recovery due to the reductions in ODS emissions achieved through the Montreal Protocol. However, due to the long atmospheric lifetime of some ODSs, full recovery is expected to take several decades.
Topic 6.3: Photochemical Smog
Knowledge and Understanding:
Primary pollutants from the combustion of fossil fuels include carbon monoxide, carbon dioxide, black carbon (soot), unburned hydrocarbons, oxides of nitrogen, and oxides of sulfur.
In the presence of sunlight, secondary pollutants are formed when primary pollutants undergo a variety of reactions with each other and with other gases already present in the atmosphere.
Tropospheric ozone (O₃) is a key secondary pollutant formed when oxygen atoms released from nitrogen dioxide (NO₂) by sunlight react with oxygen molecules (O₂). Although stratospheric ozone is beneficial, tropospheric ozone is a major component of photochemical smog and is harmful.
Other secondary pollutants include peroxyacetyl nitrate (PAN) and various aldehydes.
The formation of photochemical smog is influenced by factors such as topography, population density, and climate. Areas trapped by a layer of warm air above a layer of cooler air (temperature inversion) can experience increased smog levels as pollutants are trapped near the ground instead of being dispersed by normal air movements.
Photochemical smog has significant effects:
It can damage human health, causing respiratory problems, eye irritation, and other health issues.
It can damage vegetation, reducing crop yields and harming ecosystems.
Pollution management strategies to reduce photochemical smog include:
Reducing the burning of fossil fuels. This can be achieved by:
Using less private transport and increasing the use of public transport.
Switching to cleaner fuels or renewable energy sources.
Regulating and reducing pollutants at the point of emission. This involves:
Using catalytic converters in vehicles to reduce emissions of nitrogen oxides, carbon monoxide, and hydrocarbons.
Implementing stricter controls on industrial emissions.
Regulating the quality of fuels.
Adopting altering human activity such as encouraging walking and cycling in urban areas.
Economic incentives can also play a role by making polluting activities more expensive.
Clean-up and restoration efforts, such as tree planting which can absorb some pollutants, can have a limited effect on smog.
Legislation and government regulation are crucial in setting and enforcing emission standards.
Topic 6.4: Acid Deposition
Knowledge and Understanding:
The combustion of fossil fuels produces sulfur dioxide and oxides of nitrogen as primary pollutants.
These primary pollutants may undergo chemical processes in the atmosphere involving oxidation and mixing with water, leading to the formation of sulfuric acid and nitric acid. These acids are the main components of acid deposition.
Acid deposition can occur in the form of acid rain, snow, fog, and dry deposition (acidic particles).
Acid deposition has several direct and indirect effects, including:
Direct effects:
Acidification of lakes and rivers, leading to the death of aquatic organisms. Different species have different tolerances to acidity. Aluminum ions, leached from the soil by acidic water, can also be toxic to fish.
Direct damage to forests, especially at higher elevations where trees are exposed to acidic fog and clouds. Acid deposition can leach nutrients from the soil and damage leaves, making trees more vulnerable to disease, pests, and harsh weather.
Damage to buildings and infrastructure, particularly those made of limestone or marble, which are eroded by acid rain. Metals can also be corroded.
Direct effects on vegetation and crops by damaging leaves and reducing photosynthesis.
Indirect effects:
Leaching of essential nutrients (like calcium and magnesium) from the soil, making them unavailable to plants.
Release of toxic metals (like aluminum and mercury) from the soil into water bodies, which can be harmful to aquatic life and can bioaccumulate in food chains.
Nutrient pollution in some cases, as nitrogen oxides can contribute to excessive nitrogen in ecosystems, leading to eutrophication in coastal waters.
The effects of acid deposition may be limited to areas downwind of major industrial regions because pollutants can be transported long distances by prevailing winds. This highlights the cross-border nature of the problem. For example, Scandinavian forests and lakes have been significantly affected by emissions from industrial areas in Europe.
Pollution management strategies for acid deposition include:
Altering human activity by reducing the consumption of fossil fuels through energy conservation, using public transportation, and switching to renewable energy sources.
Regulating and reducing pollutants at the point of emission. This involves:
Using catalytic converters in vehicles to reduce nitrogen oxide emissions.
Implementing flue gas desulfurization (scrubbers) in power plants to remove sulfur dioxide before it is released into the atmosphere.
Regulating fuel quality to reduce sulfur content.
Clean-up and restoration measures, such as:
Liming acidified lakes and soils to neutralize the acidity. However, this is a temporary solution and can have other ecological consequences.
Reforestation efforts in damaged areas.
International agreements and national legislation to set emission reduction targets for sulfur dioxide and nitrogen oxides are crucial for addressing acid deposition on a larger scale.
TOPIC 7: CLIMATE CHANGE AND ENERGY PRODUCTION
Topic 7.1: Energy Choices and Security
Knowledge and Understanding:
Fossil fuels (coal, oil, and natural gas) are a significant part of the global energy supply, but their combustion contributes to air pollution and greenhouse gas emissions, leading to climate change. Their availability is also finite.
Sources of energy with lower carbon dioxide emissions than fossil fuels include nuclear power, renewables (solar, wind, hydro, biomass, geothermal, wave, and tidal power). The use of nuclear power has a low carbon emission, but issues of nuclear waste disposal and the potential for accidents are concerns. Renewable energy sources are generally more sustainable but can have their own environmental impacts and may be intermittent.
A country's degree of energy security depends on its independence and the reliability of supply of energy resources. An unreliable or inadequate energy supply can lead to economic and social instability.
The energy choices adopted by a society may be influenced by factors such as:
Availability of resources: Some regions have abundant fossil fuel reserves, while others have greater potential for renewable energy.
Sustainability: Growing awareness of environmental impacts is driving a shift towards more sustainable energy sources.
Technological development: Advances in renewable energy technologies are making them more efficient and cost-competitive.
Cultural attitudes and political factors: Public opinion and government policies play a significant role in energy choices.
Economic factors: The cost of energy production, infrastructure requirements, and market prices influence decisions.
Environmental factors: Concerns about pollution and climate change are major drivers for change.
Improvements in energy efficiencies and energy conservation can significantly limit growth in energy demand and contribute to energy security and sustainability.
Energy security can be affected by various factors, including:
Political stability of energy-supplying countries: Dependence on politically unstable regions can create vulnerabilities.
Security of transportation infrastructure: Disruptions to oil and gas pipelines or shipping routes can impact supply.
Diversity of energy sources and suppliers: Relying on a single source or supplier increases risk.
Infrastructure resilience: The ability of energy infrastructure to withstand disruptions (e.g., cyberattacks, natural disasters) is crucial.
Energy storage capabilities: Developing effective energy storage solutions can help address the intermittency of some renewable sources.
Topic 7.2: Climate Change — Causes and Impacts
Knowledge and Understanding:
Climate is the average weather over many years, and the difference between weather and climate is the timescale on which they are considered. Weather refers to short-term atmospheric changes, while climate looks at long-term trends.
The Earth's climate has naturally varied. These variations can be caused by natural factors.
However, there is compelling evidence that human activities are significantly contributing to recent climate change, primarily through the enhanced greenhouse effect.
Human activities increase the levels of greenhouse gases in the atmosphere. Key greenhouse gases include carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O).
Sources of increased greenhouse gases due to human activities include:
Burning of fossil fuels.
Agriculture (e.g., cattle release methane).
Deforestation.
Ocean and atmospheric circulatory systems play a significant role in climate. These systems distribute heat and influence weather patterns globally. Changes in temperature can affect these systems. For example, the El Niño Southern Oscillation (ENSO) is a natural variation in the Pacific Ocean that affects global weather.
Feedback mechanisms can amplify or dampen the initial warming due to greenhouse gas emissions.
Positive feedback: Melting ice reduces reflectivity (albedo), leading to more absorption of solar radiation and further warming. Warmer temperatures can also lead to increased evaporation, potentially leading to more clouds that trap heat. Increased methane release from thawing permafrost is another positive feedback.
Negative feedback: Increased evaporation can also lead to more clouds that reflect sunlight, causing cooling. Increased CO₂ in the atmosphere can lead to increased photosynthesis in plants, removing some CO₂.
There has been debate about the causes of climate change, with some emphasizing natural variations. However, the prevailing scientific view, supported by organizations like the IPCC, is that human activities are the primary driver of the accelerated warming trend. Evaluating different viewpoints requires considering the evidence and the credibility of sources.
Global climate models are used to predict future climate scenarios. These models incorporate complex interactions within the climate system and are based on scientific understanding and data. They help project the potential impacts of greenhouse gas emissions.
Observed impacts of climate change include:
Rising global temperatures.
Changes in precipitation patterns.
More frequent and intense extreme weather events.
Melting glaciers and ice sheets.
Sea level rise.
Ocean acidification (not explicitly mentioned in section 7.2 but is a known impact).
Changes in species distribution and behavior (mentioned in other sections like 2.4 and 3.3).
The long-term record shows fluctuations in temperature and atmospheric CO₂ concentrations, with recent increases being particularly rapid and coinciding with increased human emissions.
Different greenhouse gases have varying global warming potentials and atmospheric lifetimes.
Topic 7.3: Climate Change — Mitigation and Adaptation
Knowledge and Understanding:
Mitigation involves efforts to reduce or prevent the emission of greenhouse gases (GHGs). This generally focuses on addressing the causes of the enhanced greenhouse effect discussed in Topic 7.2.
Mitigation strategies to reduce CO₂ emissions include:
Reducing energy consumption.
Reducing emissions of oxides of nitrogen and methane from agriculture.
Using alternatives to fossil fuels. This includes renewable energy sources like solar, wind, and geothermal.
Geo-engineering or climate engineering involves large-scale, intentional interventions in the Earth's climate system to limit climate change.
Increasing carbon dioxide removal (CDR) or carbon capture and storage (CCS) from the atmosphere.
Strategies to stabilize or reduce GHGs should include:
Reduction of energy use.
Reduction of emissions of GHGs (carbon dioxide, methane and oxides of nitrogen).
Increasing the uptake of atmospheric carbon (carbon sinks). This includes protecting and enhancing forests and other vegetation.
Further mitigation strategies for carbon dioxide removal (CDR) include:
Increase of photosynthesis so that more atmospheric carbon is stored in biomass (carbon sinks).
Using carbon capture and storage (CCS) technology at fossil fuel power stations.
Increasing the use of biomass as a fuel.
Enhancing natural carbon sinks, such as oceans and forests.
Other mitigation strategies include:
Reducing methane production and release. This can be achieved by managing livestock and landfill sites.
Reducing the use of nitrogen fertilizers to limit nitrous oxide emissions.
Reducing the release of fluorinated gases (F-gases), which are powerful greenhouse gases used in various industrial applications.
Adaptation involves adjusting to the current and future effects of climate change. The goal is to reduce our vulnerability to its harmful effects and take advantage of any potential beneficial opportunities.
Examples of adaptation strategies can be diverse and context-specific, depending on the region and the anticipated impacts. These may include:
Developing more drought-resistant crops.
Managing water resources more efficiently in areas facing water scarcity.
Building sea walls and other defenses in coastal areas threatened by sea-level rise.
Improving public health systems to deal with heatwaves and the spread of vector-borne diseases.
Adjusting infrastructure to cope with more extreme weather events.
There has been significant debate about the best strategies for mitigating and adapting to climate change. This debate often involves economic, social, and political considerations.
Global climate models (EVMs) play a role in informing both mitigation and adaptation strategies by projecting potential future climate scenarios and the effectiveness of different actions.
International efforts to reduce climate change are crucial due to the global nature of the problem. These efforts involve agreements, policies, and collaborations between countries to set emission reduction targets and promote sustainable development.
The Kyoto Protocol (effective from 2005) is mentioned as an international agreement setting targets for industrialized countries to cut their GHG emissions. However, it had limitations, including the lack of binding targets for all major emitters.
The text also mentions subsequent efforts and ongoing discussions at international forums. The effectiveness of these efforts is a subject of ongoing evaluation.
TOPIC 8: HUMAN SYSTEMS AND RESOURCE USE
Topic 8.1: Human Population Dynamics
Knowledge and Understanding:
Demographic data is crucial for quantifying human population dynamics. Key indicators include:
Crude Birth Rate (CBR): The number of births per 1,000 population per year.
Crude Death Rate (CDR): The number of deaths per 1,000 population per year.
Fertility Rate (FR): The number of live births per woman of childbearing age (usually 15-49 years).
Doubling Time (DT): The number of years it would take for a population to double at its current rate of natural increase.
Natural Increase Rate (NIR): The percentage growth of a population in a year, calculated as (CBR - CDR) / 10.
Global human population growth has followed an exponential pattern, particularly in recent centuries. This means the rate of increase is proportional to the size of the population, leading to increasingly rapid growth.
Age-gender pyramids are graphical representations of the age and sex structure of a population at a given point in time. Their shape can indicate whether a population is growing, stable, or declining, and provide insights into future population trends.
The Demographic Transition Model (DTM) is a framework that describes the historical shift of birth and death rates in industrialized societies from high to low levels. It typically has four stages (and sometimes a fifth is considered) reflecting changes in population growth patterns as societies develop.
Various factors influence human population dynamics:
Cultural factors: Societal norms and traditions related to family size, marriage, and the role of women can affect fertility rates.
Historical factors: Past events like wars, famines, and epidemics can have long-lasting impacts on population structure and growth.
Religious factors: Religious beliefs and practices can influence attitudes towards family planning and contraception, impacting birth rates.
Social factors: Education levels (especially for women), access to healthcare, urbanization, and social security systems can all affect population dynamics.
Political factors: Government policies related to family planning, immigration, and social welfare can significantly influence population growth and structure.
Economic factors: Economic development, employment opportunities, the cost of raising children, and the availability of resources can impact fertility and migration patterns.
National and international development policies can have significant impacts on population growth. For example, policies promoting education for girls and access to family planning often lead to lower fertility rates. Conversely, policies encouraging larger families can increase birth rates. Immigration policies directly affect population size and structure.
Population projections are estimates of future population size and composition based on current trends in fertility, mortality, and migration. These projections are subject to uncertainty due to the complexity of factors influencing population change.
Policies that may reduce population growth include those that:
Improve access to education for women.
Increase the availability of contraception and family planning services.
Lower infant and child mortality rates.
Provide economic incentives for smaller families.
Policies that may increase population growth include those that:
Offer financial incentives for having more children.
Restrict access to contraception and abortion.
Encourage immigration.
Topic 8.2: Resource Use in Society
Knowledge and Understanding:
Natural capital refers to natural resources that have value to humans. These resources can produce sustainable income in the form of natural income.
Renewable natural capital can be replenished over time through natural processes at a rate comparable to or faster than its rate of consumption by humans. Examples include living organisms (forests, fish stocks), solar radiation, wind, and water flow. These are self-sustaining and can provide a continuous yield.
Non-renewable natural capital exists in finite quantities on Earth and cannot be renewed or replenished at a rate comparable to its consumption. Examples include fossil fuels (coal, oil, gas) and minerals. Their use depletes the stock.
The economic value of natural capital can be derived from its ecological functions (e.g., water purification, flood protection), recreational uses, and direct consumption of resources.
The concept of natural capital is dynamic because the status and value of resources can change over time due to factors such as:
Technological advancements. For example, new extraction technologies can make previously inaccessible resources available.
Changing human needs and values. Resources that were once considered worthless may become valuable, and vice versa.
Environmental degradation and resource depletion. Overexploitation can reduce the availability and value of natural capital.
Patterns of resource consumption differ significantly between societies. Factors influencing these patterns include:
Economic development. More developed societies generally have higher rates of resource consumption.
Cultural norms and lifestyles. Different cultural practices can lead to variations in resource use.
Population density and growth. Larger and faster-growing populations tend to consume more resources.
Availability of resources. Societies with abundant local resources may have different consumption patterns than those that rely on imports.
Environmental policies and regulations. Government measures can influence resource use through restrictions, incentives, and pricing mechanisms.
Topic 8.3: Solid Domestic Waste
Knowledge and Understanding:
Solid domestic waste (SDW), also known as municipal solid waste (MSW), consists of waste materials discarded from households and commercial and governmental sources. This includes items such as food waste, paper, packaging, plastics, textiles, and electronic waste (e-waste).
The volume of SDW produced per capita varies significantly between more economically developed countries (MEDCs) and less economically developed countries (LEDCs). Generally, MEDCs produce more SDW per person.
There are various SDW disposal options, including:
Landfill: The most common method in many areas, involving burying waste.
Incineration: Burning waste at high temperatures, which can reduce its volume but may release air pollutants.
Recycling: Processing used materials into new products, reducing the need for raw materials and lowering landfill volume. This includes materials like plastics, paper, glass, and metals.
Composting: Decomposing organic waste (e.g., food scraps, yard waste) to create a nutrient-rich soil amendment.
Pollution management strategies for SDW aim to minimize the negative environmental and health impacts of waste. These strategies can be categorized as:
Altering human activity (Reduce): This involves reducing the amount of waste produced in the first place through measures such as consuming less, buying products with less packaging, and reusing items.
Controlling release of pollutant (Regulate and Recover): This includes measures implemented at the point of waste management, such as collecting and properly treating leachate from landfills, capturing methane gas produced in landfills for energy generation, and sorting waste for recycling. Incineration with proper emission controls also falls under this category.
Clean-up and restoration (Remediate): This involves actions taken after waste has been disposed of, such as reclaiming and restoring closed landfill sites for other uses.
The effectiveness of different SDW pollution management strategies depends on various factors, including economic feasibility, social acceptance, environmental impact, and the specific characteristics of the waste stream. A combination of strategies is often the most effective approach. The concept of a circular economy, where resources are kept in use for as long as possible, extracting the maximum value from them whilst in use, then recovering and regenerating products and materials at the end of each service life, is a sustainable approach to managing SDW.
Topic 8.4: Human Systems and Resource Use
Knowledge & Understanding (Summary)
Carrying capacity: Max population a given area can sustainably support.
Estimating human carrying capacity is hard due to varying lifestyles, tech use, trade, and resource substitution.
Ecological Footprint (EF): Land/water needed to support a population’s resource use and waste. EF is a model to estimate human environmental demands.
EFs vary by country/person due to lifestyle, food production, land use, and industry.
If EF > available land, population is unsustainable and over carrying capacity.
Environmental degradation and finite resources limit population growth.
Exceeding carrying capacity risks collapse.
Why Human Carrying Capacity is Hard to Measure:
Humans use diverse and changing resources.
Substitution (e.g. oil → solar) complicates calculations.
Resource needs vary with culture, lifestyle, economy.
Global trade/imports extend local capacity but don’t affect global limits.
Technology changes resource availability but may cause long-term environmental damage.
Too many variables make reliable estimates nearly impossible.
Ways to Change Human Carrying Capacity:
Economists: Promote resource substitution and self-sufficiency (e.g., solar, water recycling).
Technocentrists: Believe innovation can continuously expand carrying capacity.
Efficiency: Using resources more efficiently can extend availability but only if population stays constant.
Ecological economists: Warn tech may boost short-term yields but harm long-term natural capital (e.g., soil erosion).
Sustainability must consider both innovation and resource limits.
Ecological Footprints (EF):
EF = area needed to support a population’s resource use and waste.
Varies widely by country and individual.
In 2012, global EF = 1.5 Earths; we’ve exceeded limits since the 1970s.
WWF and Global Footprint Network track EF by country.
High EF linked to high consumption, fossil fuel use, imports, and waste.
EF includes land for crops, grazing, timber, carbon sequestration, etc.
Countries can exceed local carrying capacity through imports/trade.
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