Defaunation

Defaunation is the loss of animal species or populations from an ecosystem, especially through human activity. It includes local population declines and species extinction.

Overexploitation: The use of wild species at rates faster than their populations can recover. Hunting and harvesting directly deplete animal populations.
Seed dispersal: The movement of seeds away from their parent plants by wind, water, or animals. Loss of fruit-eating animals can reduce the movement and establishment of plant seeds.
Passenger pigeon: An abundant North American pigeon driven to extinction in the early twentieth century. Its collapse shows how commercial hunting can eliminate even extraordinarily numerous animals.
Deforestation: The removal or conversion of forest, usually through human activity. Deforestation removes habitat; defaunation can also occur in forests that remain standing.
Living Planet Index: A measure tracking average changes in monitored vertebrate population sizes over time. Its population trends offer one way to quantify declines, though they do not directly count extinctions.
Habitat fragmentation: The division of continuous habitat into smaller, isolated patches. Fragmentation restricts movement and makes animal populations more vulnerable to decline.
Pollination: The transfer of pollen between flowers that enables fertilization in seed plants. Declines in animal pollinators can impair reproduction in dependent plants.
Bison: Large bovine mammals native to North America and parts of Europe and Asia. The near-extermination of North American bison sharply reduced a dominant grazer population.
Devegetation: The loss or substantial reduction of plant cover in an area. Devegetation concerns plants, while defaunation concerns animals.
Biodiversity monitoring: The repeated observation of organisms and ecosystems to detect changes over time. Incomplete monitoring makes the scale and speed of defaunation difficult to estimate.

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