Greenhouse Effect, Nutrient Cycles, and Ecosystem Dynamics

Greenhouse Effect

A natural process where certain gases in the Earth's atmosphere trap heat, preventing it from escaping back into space.

Greenhouse Gases

Gases that allow sunlight to enter the atmosphere but inhibit the escape of heat, leading to global warming.

Carbon Dioxide (CO₂)

Released from burning fossil fuels, deforestation, and various industrial processes; the most significant long-lived greenhouse gas.

Methane (CH₄)

Emitted during the production and transport of coal, oil, and natural gas, as well as from livestock; over 25 times more effective than CO₂ at trapping heat over a 100-year period.

Nitrous Oxides (NOx)

Produced from agricultural and industrial activities and combustion of fossil fuels; contribute to global warming and air pollution.

Chlorofluorocarbons (CFCs)

Synthetic compounds used in refrigeration and aerosol propellants; potent greenhouse gases that deplete the ozone layer.

Enhanced Greenhouse Effect

The increase in greenhouse gases due to human activities, linked to climate change and resulting in extreme weather patterns and ecological disruptions.

Phosphorus Cycle

Describes the movement of phosphorus through the environment, primarily through rocks, soil, water, and living organisms.

Phosphate (PO₄³⁻)

The inorganic form of phosphorus found in rocks and minerals, released through weathering processes.

Nitrogen Cycle

Involves the transformation of nitrogen through various forms and locations, making it available for biological use.

Nitrogen Fixation

The process of converting nitrogen gas (N₂) into biologically available forms, such as ammonium (NH₄⁺) and nitrate (NO₃⁻).

Biologically Available Nitrogen

Forms like nitrate and ammonium that can be absorbed by plants for growth and development.

Biologically Unavailable Nitrogen

Nitrogen gas (N₂) that is stable and cannot be used directly by most organisms.

Haber-Bosch Process

An industrial process that synthesizes ammonia from nitrogen gas, significantly impacting agriculture by providing fertilizers.

Algal Blooms

Rapid increases in the abundance of algae in aquatic environments, often triggered by nutrient overload and favorable conditions.

Harmful Algal Blooms (HABs)

Blooms that can produce toxins harmful to aquatic life, humans, and ecosystems, leading to decreased water quality.

Cyanobacteria

Photosynthetic bacteria that can form blooms, often referred to as blue-green algae, playing a role in nutrient cycling.

CyanoHABs

Algal blooms dominated by cyanobacteria, common in freshwater ecosystems, can lead to significant ecological and health issues.

Native Species

Organisms that have evolved in a specific environment and are adapted to local conditions.

Exotic Species

Species introduced to a new environment by human activities, which can disrupt local ecosystems.

Invasive Species

A subset of exotic species that thrive in their new environment, often outcompeting native species and causing ecological harm.

Importance of Legumes in Nitrogen Fixation

Legumes, such as beans, peas, and lentils, have a symbiotic relationship with nitrogen-fixing bacteria (Rhizobia) in their root nodules.

Role of Legumes

These bacteria convert atmospheric nitrogen (N₂) into ammonium (NH₄⁺), a form that plants can utilize for growth.

Natural process of nitrogen fixation

Enhances soil fertility, reducing the need for synthetic fertilizers.

Global Bottom-Up Pressures

Bottom-up pressures originate from the producer level, influencing the entire food web, highlighting the interconnectedness of ecosystems.

Two primary drivers of bottom-up pressures

Climate change and nutrient enrichment, both of which significantly affect food production systems.

Mechanisms of Global Warming

Greenhouse gases such as CO2, CH4, and NOx trap heat in the atmosphere, leading to an increase in global temperatures.

Relationship between greenhouse gas concentration and heat retention

Direct; as greenhouse gases increase, so does the heat retained by the Earth.

Impacts on Producers

Increased CO2 levels provide more raw materials for photosynthesis, potentially enhancing growth rates in plants and algae.

Negative impacts of climate change

Heat stress and water scarcity.

Effects of Climate Change on Agriculture and Fisheries

Crop yields may initially increase due to higher CO2, but nutritional quality may decline due to lower nitrogen and phosphorus levels.

Livestock challenges due to climate change

Face increased heat stress and disease prevalence, leading to lower quality forage and higher mortality rates.

Fisheries impacts

Affected by shifting species ranges, increased diseases, and ocean acidification, which impacts shell-forming organisms.

Overview of Nutrient Enrichment

Occurs when ecosystems are overloaded with nitrogen (N) and phosphorus (P), leading to excessive growth of producers, particularly algae.

Importance of Nitrogen and Phosphorus

Essential for the synthesis of DNA, proteins, chlorophyll, and ATP, which are critical for organismal function and growth.

Human Impact on Nutrient Cycles

The Haber-Bosch process allows for the industrial fixation of nitrogen, supporting global food production but also leading to over-fertilization and environmental degradation.

Consequences of over-fertilization

Can result in reduced biodiversity, groundwater contamination, and the creation of dead zones in aquatic environments.

Economic Costs of Climate Change

Climate-related impacts on agriculture and food systems in the U.S. are estimated to cost around $750 billion annually.

Eutrophication

Driven by nutrient-rich runoff, leads to explosive algal growth, creating dead zones in aquatic environments.

Harmful algal blooms (HABs)

Can produce toxins that are detrimental to human health, wildlife, and the overall ecosystem.

Bison as Keystone Species

Bison played a crucial role in maintaining plant diversity and nutrient cycling within their ecosystems.

Top-Down Pressures

Arise from human activities that remove or add consumers to ecosystems, significantly impacting food webs.

Current extinction rate

Estimated to be 1,000-10,000 times the natural rate, indicating a severe biodiversity crisis.

Causes of Species Loss

Major causes include invasive species, land and sea use changes, climate change, pollution, and over-exploitation.

Invasive Species

Exotic species that reproduce and spread in a new environment, often disrupting food webs.

Habitat Fragmentation

Due to agriculture and urban development affects 85% of threatened species, leading to decreased biodiversity.

Over-exploitation

Humans overharvest species for food, trophies, medicine, or political aims, impacting ecosystem dynamics.

6th Mass Extinction

Many scientists believe we are currently in a 6th mass extinction event caused by invasive species, land and sea use changes, climate change, pollution, and over-exploitation.

CyanoHAB

Harmful algal bloom made of cyanobacteria, which can produce cyanotoxins harmful to humans and animals.

Phosphorus Cycle

No gaseous phase; cycles locally, sourced through mining and weathering.

Keystone species

Species that have a disproportionately large effect on ecosystem structure.

Cyanotoxins

Toxic compounds made by cyanobacteria; harmful to humans and animals.

Legumes

Plants like soybeans and beans that host Rhizobia bacteria for nitrogen fixation.

10% Rule

Only ~10% of energy transfers to the next trophic level in a food web.

Dead Zones

Occur when excess nutrients cause algal blooms, leading to oxygen depletion and making water uninhabitable for most organisms.