Defaunation

Defaunation is the global, local or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed 'empty forest'. Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. 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. Since then, the term has gained broader usage in conservation biology as a global phenomenon. Defaunation is the global, local or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed 'empty forest'. Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. 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. Since then, the term has gained broader usage in conservation biology as a global phenomenon. It is estimated that more than 50 percent of all wildlife has been lost in the last 40 years. in 2020 it is estimated that 68% of the world's wildlife will be lost. In South America, there is believed to be a 70 percent loss. 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.' The intensive hunting and harvesting of animals threatens endangered vertebrate species across the world. Game vertebrates are considered valuable products of tropical forests and savannas. In Brazilian Amazonia, 23 million vertebrates are killed every year; large-bodied primates, tapirs, white-lipped peccaries, giant armadillos, and tortoises are some of the animals most sensitive to harvest. Overhunting can reduce the local population of such species by more than half, as well as reducing population density. Populations located nearer to villages are significantly more at risk of depletion. Abundance of local game species declines as density of local settlements, such as villages, increases. Hunting and poaching may lead to local population declines or extinction in some species. Most affected species undergo pressure from multiple sources but the scientific community is still unsure of the complexity of these interactions and their feedback loops. One case study in Panama found an inverse relationship between poaching intensity and abundance for 9 of 11 mammal species studied. In addition, preferred game species experienced greater declines and had higher spatial variation in abundance. Human population growth results in changes in land-use, which can cause natural habitats to become fragmented, altered, or destroyed. Large mammals are often more vulnerable to extinction than smaller animals because they require larger home ranges and thus are more prone to suffer the effects of deforestation. Large species such as elephants, rhinoceroses, large primates, tapirs and peccaries are the first animals to disappear in fragmented rainforests. A case study from Amazonian Ecuador analyzed two oil-road management approaches and their effects on the surrounding wildlife communities. The free-access road had forests that were cleared and fragmented and the other had enforced access control. Fewer species were found along the first road with density estimates being almost 80% lower than at the second site that which had minimal disturbance. This finding suggests that disturbances affected the local animals' willingness and ability to travel between patches. Fragmentation lowers populations while increasing extinction risk when the remaining habitat size is small. When there is more unfragmented land, there is more habitat for more diverse species. A larger land patch also means it can accommodate more species with larger home ranges. However, when patch size decreases, there is an increase in the number of isolated fragments which can remain unoccupied by local fauna. If this persists, species may become extinct in the area.