Ecosystem Services
The benefits that humans derive from properly functioning ecosystems, including provisioning services (food, water), regulating services (climate regulation, flood control), cultural services (recreation, spiritual value), and supporting services (nutrient cycling, soil formation). These services are often taken for granted until they are degraded or lost.
Example: Wetlands provide water filtration services worth billions of dollars annually. When wetlands are drained for development, communities must invest in expensive water treatment infrastructure to replace the natural purification process.
Biogeochemical Cycles
The pathways through which chemical elements and compounds move between living organisms and the nonliving environment. The major cycles include the carbon, nitrogen, phosphorus, and water cycles, each involving biological, geological, and chemical processes that regulate the availability of essential nutrients.
Example: The carbon cycle moves carbon through the atmosphere as CO2, into plants via photosynthesis, through food webs, into soil and ocean sediments, and back into the atmosphere through respiration, decomposition, and combustion of fossil fuels.
Biodiversity
The variety of life at all levels of biological organization, including genetic diversity within species, species diversity within communities, and ecosystem diversity across landscapes. Biodiversity underpins ecosystem stability and resilience, and its loss can trigger cascading ecological consequences.
Example: The Amazon rainforest contains approximately 10% of all species on Earth. Deforestation there reduces not only local species richness but also disrupts rainfall patterns across South America through reduced evapotranspiration.
Climate Change
Long-term shifts in global temperatures and weather patterns driven primarily by the increased concentration of greenhouse gases in the atmosphere from burning fossil fuels, deforestation, and industrial processes. The enhanced greenhouse effect traps additional heat, raising average global temperatures and altering precipitation patterns.
Example: Since the pre-industrial era, atmospheric CO2 has risen from about 280 ppm to over 420 ppm, contributing to approximately 1.1 degrees Celsius of global warming and causing measurable sea-level rise, glacier retreat, and increased frequency of extreme weather events.
Carrying Capacity
The maximum population size of a species that an environment can sustain indefinitely given the available food, habitat, water, and other resources. When a population exceeds its carrying capacity, resource depletion and environmental degradation accelerate, often resulting in population decline.
Example: Reindeer introduced to St. Matthew Island in the Bering Sea grew from 29 individuals in 1944 to over 6,000 by 1963, far exceeding the island's carrying capacity. The population crashed to 42 animals by 1966 after overgrazing destroyed the lichen food supply.
Sustainability
The practice of meeting present needs without compromising the ability of future generations to meet their own needs. Sustainability requires balancing economic growth, social equity, and environmental protection, often described as the three pillars or triple bottom line.
Example: Sustainable forestry practices such as selective logging and replanting programs allow timber companies to harvest wood products while maintaining forest health, biodiversity, and carbon storage capacity for future generations.
Trophic Levels
The hierarchical positions organisms occupy in a food chain, determined by their energy source. Primary producers form the base, followed by primary consumers (herbivores), secondary consumers (carnivores), and tertiary consumers (top predators). Energy is lost at each transfer, typically about 90%, limiting the number of trophic levels.
Example: In a marine ecosystem, phytoplankton (producers) are eaten by zooplankton (primary consumers), which are eaten by small fish (secondary consumers), which are eaten by tuna (tertiary consumers). This explains why tuna are far less abundant than the plankton that ultimately support them.
Environmental Impact Assessment
A systematic process used to evaluate the potential environmental consequences of a proposed project, plan, or policy before a decision is made. EIAs identify direct, indirect, and cumulative impacts and propose mitigation measures to minimize environmental harm.
Example: Before constructing a new highway through a forested area, an EIA might reveal that the route would fragment habitat for endangered species, leading planners to redesign the route with wildlife corridors and overpasses to reduce ecological disruption.
