Friday, 29 July 2016

Loss of habitats and local species extinctions

Study of extinction rates following habitat loss offers hope that some species can be saved

Date: July 25, 2016
Source: University of Utah

Unfortunately, loss of plant and animal habitat leads to local species extinctions and a loss of diversity from ecosystems. Fortunately, not all of the extinctions occur at once. Conservation actions may still be able to save threatened species, according to William Newmark, a vertebrate zoologist at the Natural History Museum of Utah at the University of Utah.

In the study, published today in Nature Communications, Newmark and colleagues complied data from biodiversity and extinction reports, finding that patterns of species loss following habitat disruption are similar among birds, mammals, plants, reptiles and invertebrates. Newmark and colleagues also found that while species loss commences quickly, timely action could slow extinction rates and save species.

In deep debt
When natural habitats are lost, species lose the physical space and resources they need to continue growing and expanding. Habitats are usually lost due to human activity, such as building roads or clear-cutting a forest. After such a disturbance, the habitat can no longer support the number of species that live there and species begin to disappear until the habitat reaches a new normal. The difference between the old and new amounts of biodiversity the habitat can support is called the "extinction debt."

The research team, which included John M. Halley and Nikolaos Monokrousos from the University of Ioannina, and Antonios D. Mazaris and Despoina Vokou from the University of Thessaloniki, reviewed 43 previous studies spanning 1971 to present that included descriptions of biodiversity loss following habitat fragmentation in five taxonomic groups: mammals, plants, birds, reptiles and invertebrates.

Newmark and his colleagues found a shallow J-shaped curve, nearly identical in each taxonomic group, that described how the rates of extinction loss change over time. At first, extinction rates are high, and then decelerate until the point at which half of the extinction debt is paid off. After that point, species loss continues but at a slower rate until a new equilibrium is reached.

Several factors influence the timeline in which the biodiversity loss process plays out, but Newmark says that all groups they studied, even those thought to be resistant to extinction such as plants, showed the same pattern. These similar patterns emerge if species loss is calculated in terms of average population size and time for a new generation to arise for these taxonomic groups.

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