Biodiversity, a contraction of "biological diversity," generally refers to the variety and variability of life on Earth. One of the most widely used definitions defines it in terms of the variability within species, between species, and between ecosystems. It is a measure of the variety of organisms present in different ecosystems. This can refer to genetic variation, ecosystem variation, or species variation (number of species) within an area, biome, or planet.
This section looks at the multiple threats human activity poses to the Earth’s biodiversity, such as habitat destruction, genetic pollution, overexploitation, hybridization, climate change, human overpopulation.