Defaunation
Defaunation is the global, local, or functional extinction of animal populations or species from ecological communities.[4] The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment.[5] This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest".[6][5][7] Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance.[8] Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of Neotropical forests.[9] Since then, the term has gained broader usage in conservation biology as a global phenomenon.[4][9]
It is estimated that more than 50 percent of all wildlife has been lost in the last 40 years.[10] In 2016, it was estimated that by 2020, 68% of the world's wildlife would be lost.[11] In South America, there is believed to be a 70 percent loss.[12] A 2021 study found that only around 3% of the planet's terrestrial surface is ecologically and faunally intact, with healthy populations of native animal species and little to no human footprint.[13][14]
In November 2017, over 15,000 scientists around the world issued a second warning to humanity, which, among other things, urged for the development and implementation of policies to halt "defaunation, the poaching crisis, and the exploitation and trade of threatened species."[15]
Global patterns[edit]
Tropical regions are the most heavily impacted by defaunation.[4][5][9] These regions, which include the Brazilian Amazon, the Congo Basin of Central Africa, and Indonesia, experience the greatest rates of overexploitation and habitat degradation.[8] However, specific causes are varied, and areas with one endangered group (such as birds) do not necessarily also have other endangered groups (such as mammals, insects, or amphibians).[32]
Deforestation of the Brazilian Amazon leads to habitat fragmentation and overexploitation. Hunting pressure in the Amazon rainforest has increased as traditional hunting techniques have been replaced by modern weapons such as shotguns.[5][33] Access roads built for mining and logging operations fragment the forest landscape and allow hunters to move into forested areas which previously were untouched.[33] The bushmeat trade in Central Africa incentivizes the overexploitation of local fauna.[5] Indonesia has the most endangered animal species of any area in the world.[34] International trade in wild animals, as well as extensive logging, mining and agriculture operations, drive the decline and extinction of numerous species.[34]
Ecological impacts[edit]
Genetic loss[edit]
Inbreeding and genetic diversity loss often occur with endangered species populations because they have small and/or declining populations. Loss of genetic diversity lowers the ability of a population to deal with change in their environment and can make individuals within the community homogeneous. If this occurs, these animals are more susceptible to disease and other occurrences that may target a specific genome. Without genetic diversity, one disease could eradicate an entire species. Inbreeding lowers reproduction and survival rates. It is suggested that these genetic factors contribute to the extinction risk in threatened/endangered species.[35]