Biodiversity refers to the number of species, the number of different ecological roles played by those species, or the amount of genetic diversity encompassed by those species, either in a particular area, or over the entire Earth. Changes in biodiversity affect species interactions and the structure of ecosystems through time.
Biodiversity is affected by many Earth system processes and phenomena, including:
- Evolutionary processes that generate new species traits.
- Extinction, which decreases biodiversity.
- Species interactions, especially when species depend on other organisms for food, shelter, or compete for food, space, or nesting sites.
- Climatic conditions, such as the amount of sunlight absorbed at different latitudes, temperature, and precipitation patterns, which determine species ranges.
- Nutrients, especially nitrogen and phosphorus, which when limited can decrease biodiversity.
- Numerous other abiotic environmental factors, including soil quality, wildfires, water acidity, and oxygen levels, all of which can limit the survival, growth, reproduction and death of species populations.
- Events, such as extreme weather or volcanic eruptions, can kill individuals or entire populations of organisms.
Humans have affected biodiversity through a variety of activities, including:
- Deforestation, habitat destruction, and urbanization, which reduce the space and resources available for organisms.
- Agricultural activities that remove native species from land to make room for livestock and crops for human consumption.
- Fishing and hunting which can reduce local biodiversity by causing local extinctions.
- Human freshwater use, which can limit the amount of water available for other species in an ecosystem, reducing local biodiversity.
- The release of pollutants and waste into ecosystems that harm the reproduction or survival of organisms, which can reduce local biodiversity.
- Activities that have caused global warming, such as the burning of fossil fuels, agricultural activities, and deforestation. Increased average global temperatures have altered seasonal temperature and precipitation patterns, as well as the distribution of snow and ice cover, which can affect species ranges and regional biodiversity.
- Introducing invasive species that outcompete native species for food, water, or other resources.
Can you think of additional cause and effect relationships between biodiversity and other parts of the Earth system?
Visit the evolution, species interactions, and life cycles and traits pages to explore more connections between the biosphere and global changes.
Links to Learn More
- American Museum of Natural History: What is biodiversity?
- PBS News Hour: Biodiversity loss accelerates with 1 million species at risk of extinction, UN report finds