Ecosystems and Human Appropriation of Net Primary Productivity

Ecosystems and the Hydrological Cycle

• Communities: Biological organisms interacting.

• Ecosystems: Interaction of organisms and the physical environment; fundamentally different from communities.

• The Great Oxygen Catastrophe exemplifies biological organisms interacting with the atmosphere.

• Cycles: Various cycles impacting the environment, each operating at different rates and interacting with each other.

Hydrological Cycle

• Transpiration: Water released from plants.

• Evaporation: Water evaporating from the ground.

• Water Cycle: Water goes from ground to air and cycles back through plants and into the ocean.

Freshwater Availability

• Limited Freshwater: Very little of the world's water is fresh water.

• Usable Portion: Only a small fraction of fresh water is accessible for drinking without significant energy input.

• Ice Lock: Most fresh water is stored as ice.

• Groundwater: Even groundwater requires pumping to access.

Resource Overuse

• Overuse: Limited fresh water resources are prone to overuse.

• Atmosphere: The usable atmosphere is a thin layer compared to the Earth's size.

• UV Protection: A larger atmosphere reflects UV rays and radiation.

Heating and Radiation

• Heating: The Earth is undergoing a heating phase.

• Radiation: Photosynthetically Active Radiation (PAR) and other radiations play a role in heating. A lot of radiation is reflected back by clouds.

• Heat Retention: Pollution traps some heat formerly reflected into space.

Light Utilization

• Light Utilization: Only 2% of light is captured by autotrophs.

• Autotrophs: Autotrophs fuel the entire planet by capturing sunlight and producing energy, which the heterotrophs utilize.

• Net Primary Productivity (NPP): Amount of energy captured by plants (autotrophs) minus their respiration needs which feeds heterotrophs.

• Global Pattern: Highest in the tropics (Amazon) and southeastern states in North America, as well as boreal forests.

• Photosynthetically Active Radiation (PAR): Flowering plants mainly harness Radiation in the terrestrial environments.

Ocean Productivity

• Ocean Productivity: Opposite to land; deserts in oceans have low productivity.

• Chlorophyll: High chlorophyll indicates high net primary productivity.

• Upwelling Zones: Nutrient-rich water upwelling leads to higher productivity.

• Light Limitation: Oceans are nutrient-limited.

• Phytoplankton: Small, floating organisms are primary producers.

Light Attenuation in Water

• Attenuation: Light decreases rapidly with depth in water.

• Primary Productivity Zone: Productivity is limited to the upper layer of water.

• Thermal Heating Current: Influences primary productivity, specially in colder water areas.

• Nutrient Limitation: Oceans are nutrient-limited due to the stratification of water, preventing the flow of nutrients to the surface where there is light.

Global Net Primary Productivity

• Global NPP: Land contributes about 55%, while oceans contribute about 45% to the global net primary productivity.

• Ecosystem Comparison: Open oceans have low productivity, while tropical rainforests have high productivity.

Ecosystem Coverage and Productivity

• Earth Coverage: Oceans cover about 65% of the Earth's surface.

• Tropical Rainforest: Tropical rainforests cover only about 3% of the globe.

• Productivity: Marshes are more productive than tropical rainforests; cultivation reduces land productivity by 75%.

Net Primary Productivity: Area vs. Ecosystem

• Ocean's Role: Oceans have low productivity per meter squared but contribute significantly due to their vast area.

• Tropical Forests: They have high productivity and a semi-large presence.

• Reefs: Reefs have low coverage but high biodiversity.

Human Use of Net Primary Productivity

• Human Appropriation: Humans use a significant portion of net primary productivity.

• Lowball Estimate: Initial estimates suggest humans use about 20% of total NPP.

• Revised Estimate: Including factors like land fallow and deforestation, humans may use about 40% of the net primary productivity and aquatic ecosystems about 25%.

• Remaining NPP: The remainder is left for other animals, plants, and fungi.

Human Appropriation of NPP

• Population Density: High population areas correlate with high NPP use.

• Urban Centers: Energy imports are necessary to sustain urban centers with high NPP consumption.

• Organism Abundance: Decreasing organism abundance is linked to reduced resources.

• Population Growth: Growing populations increase energy consumption.

Carbon Sources and Impact

• Fossil Fuels: Mobilizing petroleum introduces carbon into the atmosphere.

• Carbon Cycle: This carbon was previously deep in the Earth and not part of the active carbon cycle.

• CO2 Increase: Leads to increased $CO_2$ levels in the atmosphere.

Climate Change and CO2 Levels

• CO2 Variation: $CO_2$ levels have varied over time, but there's a clear upward trend.

• Keeling Curve: Continuous measurements of $CO_2$ levels started by David Keeling in Hawaii show a steady increase.

• Temperature Rise: Rising temperatures correlate with increasing $CO_2$ levels.

• Temperature Anomaly: Temperature anomaly since 1961 to 1990 shows variations and an upward trend.

• Multiple Data Types: Data from glaciers and other sources confirm the upward trend.

Biological Impacts of Climate Change

• Range Shifts: Species are moving to higher altitudes or latitudes (northward in the northern hemisphere).

• Phenology: The timing of biological events is changing (e.g., plants flowering earlier).

• Lilac Blooming: Lilacs in Rochester, New York, are blooming earlier due to rising temperatures.

Ocean Acidification

• CO2 Absorption: The amount of $CO_2$ in the atmosphere causes the slow shifting concentrations to the oceans.

• pH Decrease: Increasing $CO<em>2$ in the atmosphere drives increasing $CO</em>2$ in the ocean, decreasing the ocean pH, leading to ocean acidification.

• Carbonate Availability: Increasing Ocean Acidity decreases the amount of carbonate needed for shell building.

• Coral Dissolution: Acidification causes coral shells to dissolve.

• Coral Reef Decline: Coral reefs are predicted to decline and shift to non-carbonate communities.

Biodiversity and Ecosystem Function

• Importance of Biodiversity: The question is whether biodiversity matters for humans.

• Ecosystem Productivity: Does more biodiversity lead to more productive ecosystems?

• Ecosystem Services: The degree to which ecosystems function to support humans.

Ecosystem Functions and Services

• Ecosystem Functions: Processes like biomass production, decomposition, and seed dispersal.

• Ecosystem Services: Benefits ecosystems provide to humans (e.g., protein, clean water, medicines).

Relationship Between Biodiversity and Function

• Species Contribution: The relationship between the number of species and ecosystem functions

• Type 1: Each species equally contributes to ecosystem function as more and more species get added.

• Type 2: A few species provide most of the function; additional species add little to the overall system.

• Type 3: A few species do all the function.

• Real-world application: In most communities, relationships between ecosystem function is explained by type 2.

Biodiversity and Ecosystem Function Experiment

• Cedar Creek Experiment: Long-term ecological research site.

• Species Number: Plots with varying numbers of species (one to six) are used to measure productivity.

• Productivity: Adding species leads to increased productivity, following a type-two response curve.

Nitrogen and Ecosystem Function

• Nitrogen Impact: Excessive nitrogen leads to algal blooms and eutrophication.

• Plant Cover: Increasing plant species reduces nitrate levels in the rooting zone.

• Nitrate Runoff: More species means less nitrate runoff into streams.

Biodiversity Loss and Consequences

• Complexity: Communities and ecosystems are complicated and interconnected.

• Ecosystem Function: Biodiversity loss reduces ecosystem function.

Ecosystem Services: Categories and Examples

• Human-Centered View: Focus on ecosystem services and their value to human society.

• Provisioning Services: Food, fresh water, firewood.

• Regulating Services: Coastal buffering, pollination.

• Cultural Services: Tourism (e.g., whale watching, glaciers).

The Millennium Ecosystem Assessment

• Assessment: Analyzed ecosystem changes over the past 50 years and their consequences for humans.

• Habitat Loss: Significant habitat loss between 1950 and 1990.

• River Pollution: Big rivers are becoming polluted with nitrates.

• Dead Zone: The Mississippi River creates a dead zone in the Gulf of Mexico.

Changes in Ecosystem Services

• Trends: Reviewed ecosystem productivity

• Degradation: Many ecosystem services are degraded.

• Likelihood: There is an increased likelihood of abrupt ecosystem changes.

Economic Argument for Conservation

• Value: Assigning economic value to ecosystems is essential for conservation efforts.

• Cod Example: The collapse of the cod fishery cost the Canadian government $2 billion.

Mangrove Ecosystem Services

• Services: Mangroves provide essential services.

• Fish Nurseries: the mangroves act as fish nurseries where little fish evades predators and grows up

• Sediment Traps: They trap sediments.

• Pollution Detoxification: mangroves detoxify pollutants

• Erosion Control: mangroves reduce erosion in storms.

Mangrove Conversion to Shrimp Farm: A Case Study

• Comparison: Intact mangroves versus shrimp farms are compared in the study.

• Honduras: River deltas were converted to shrimp farms.

• Manoeuvre: pump fresh water out of the ocean with high volumes so they can grow shrimp at high densities.

• Value Assessment: The assessment consists of evaluating the values of both the shrimp farm and the mangrove ecosystem.

• Ecosystem Services: Essential and valuable. Even those that can not be estimated are important; however, it does not always look that way.

New York City's Water Supply

• Clean Water Source: Clean water from the Catskill Mountains is used as a source.

• Water Treatment Plant Avoidance: $6 - 8 billion expense

• Ecosystem Restoration: Instead, restoration of the Catskills led to cleaner water. NYC spent about $1.4B on watershed protection, it saved the city billions in the long-term.

Total Value of Ecosystem Services

• Global Value: Total ecosystem services are valued at $33 trillion, which is 1.8 times the global GDP.

Biosphere 2

• Experiment: An attempt to build a self-sustaining ecosystem but failed.

• Limited Success: 58% extirpation of introduced species happened after closing up the biosphere

• Comparisons: A comparison with the cost of the ecosystems and the biosphere led to the conclusion that the earth is a good deal on a per hectare basis with the resources it provides.

Public Goods and the Tragedy of the Commons

• Public Goods: Resources used by everyone.

• Overuse: Resources tend to be overused due to the lack of valuation and sense of sharing.

Tragedy of the Commons

• Concept: Shared resources tend to be overused.
  *Example: Four people share a pasture, adding cows leads to overgrazing.

• Explanation: as costs are shared amongst many, each individual feels less inhibited to exploit a shared resource for personal gain to an unsustainable extent. The asymmetry between the shared cost and the personal gain facilitates overuse.

• Solutions: Education and communication are essential (awareness of the consequences).

• Nobel Prize: A nobel price has been awarded in this type of work. The solutions come from groups discussing the problem and its awareness.