Climate Change, Biogeochemical Cycles, and Biodiversity: Study Guide

Climate Change, Biogeochemical Cycles, and Biodiversity

1. Biogeochemical Cycles and Human Impact

Biogeochemical cycles describe the movement of elements and compounds among living organisms and the environment. Human activities have significantly altered these cycles, impacting ecosystems globally.

Nitrogen Cycle

• Definition: The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms, involving the atmosphere, biosphere, and geosphere.

• Key Reservoirs: Atmosphere (N2 gas), soil, water, living organisms.

• Key Processes: Nitrogen fixation, nitrification, assimilation, ammonification, denitrification.

• Role of Organisms: Bacteria (e.g., Rhizobium), plants, and animals participate in nitrogen transformations.

• Human Impact: Use of synthetic fertilizers increases nitrogen runoff, leading to eutrophication and dead zones in aquatic systems.

Example: Excess fertilizer runoff into rivers causes algal blooms, which deplete oxygen and harm aquatic life.

Phosphorus Cycle

• Definition: The phosphorus cycle describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.

• Key Reservoirs: Rocks, soil, water, living organisms.

• Key Processes: Weathering of rocks releases phosphate ions, which are absorbed by plants and move through food webs.

• Human Impact: Fertilizer use and wastewater increase phosphorus in water bodies, causing eutrophication.

Example: Phosphorus runoff from agriculture leads to harmful algal blooms in lakes.

Carbon Cycle and Fossil Fuels

• Definition: The carbon cycle is the movement of carbon among the atmosphere, biosphere, hydrosphere, and geosphere.

• Combustion of Fossil Fuels: Releases CO2 into the atmosphere, contributing to climate change.

• 'Good News': Increased CO2 can enhance plant growth (photosynthesis) in some cases.

• 'Bad News': Excess CO2 leads to global warming, ocean acidification, and climate disruptions.

2. Human Activities and Global Climate Change

Human activities, especially the burning of fossil fuels and deforestation, are major drivers of climate change.

• Climate vs. Weather: Climate is the long-term average of weather patterns; weather is short-term atmospheric conditions.

• Why Climate is Changing Rapidly: Increased greenhouse gas emissions from human activities.

• Impacts: Rising temperatures, melting ice, sea level rise, extreme weather events.

• Feedback Effects: Positive feedback (e.g., melting ice reduces albedo, increasing warming); negative feedback (e.g., increased plant growth absorbs CO2).

Example: Thawing permafrost releases methane, a potent greenhouse gas, accelerating warming.

3. Effects of Climate Change on Organisms and Ecosystems

Climate change affects species distributions, phenology (timing of biological events), and ecosystem processes.

• Geographic Ranges: Species may shift their ranges toward the poles or higher elevations.

• Phenology: Earlier flowering, migration, or breeding in response to warming.

• Evolutionary Adaptations: Some species may evolve in response to new environmental pressures.

• Vector-borne Diseases: Changing climates can expand the range of disease-carrying organisms.

• Crop Productivity: Changes in temperature and precipitation affect agriculture.

• Ocean Acidification: Increased CO2 lowers ocean pH, harming marine life.

Example: Coral bleaching events are linked to higher ocean temperatures and acidification.

4. Responses to Climate Change

• Mitigation: Actions to reduce greenhouse gas emissions (e.g., renewable energy, reforestation).

• Adaptation: Adjusting to climate impacts (e.g., building sea walls, developing drought-resistant crops).

Example: Switching to solar and wind energy reduces CO2 emissions (mitigation); planting drought-tolerant crops helps farmers adapt to changing rainfall patterns (adaptation).

5. Threats to Biodiversity

Biodiversity is threatened by multiple human activities, leading to species extinctions and ecosystem degradation.

• Major Threats:

  • Habitat loss (e.g., deforestation, urbanization)

  • Over-harvesting (e.g., overfishing, poaching)

  • Invasive species (non-native species that disrupt ecosystems)

• Conservation Biology: The scientific study of protecting and restoring biodiversity.

• Conservation Actions: Protected areas, habitat restoration, captive breeding, legal protections.

Example: Establishing national parks to protect endangered species and their habitats.

6. Key Terms and Definitions

Term	Definition
Endangered species	Species at high risk of extinction in the near future.
Hot spot	Region with high biodiversity under significant threat from humans.
Climate change	Long-term alteration of temperature and typical weather patterns in a place.
Sustainability	Meeting current needs without compromising future generations' ability to meet theirs.
Species diversity	Variety and abundance of different species in a given area.
Resilience	Ability of an ecosystem to recover from disturbances.
Resistance	Ability of an ecosystem to remain unchanged when subjected to disturbance.
Genetic diversity	Variety of genes within a species.
Global water cycle	Movement of water among oceans, atmosphere, and land.
Global nitrogen cycle	Movement of nitrogen through the biosphere, atmosphere, and geosphere.
Global warming	Increase in Earth's average surface temperature due to rising greenhouse gases.
Nitrogen fixation	Conversion of atmospheric nitrogen (N2) into biologically usable forms by bacteria.
Phosphorus	Essential nutrient for living organisms, part of DNA, RNA, and ATP.
Habitat fragmentation	Breaking up of continuous habitat into smaller, isolated patches.
Invasive species	Non-native species that spread widely and cause harm to ecosystems.
Extinct species	Species that no longer exist anywhere on Earth.