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Bio­di­ver­sity loss raises risk of ‘extinc­tion cascades’

pub­lished 24 Feb­ru­ary 2018 | mod­i­fied 24 Feb­ru­ary 2018

waspResearchers used plants and insects, such as this par­a­sitoid wasp (aphid­ius megourae).New research shows that the loss of bio­di­ver­sity can increase the risk of “extinc­tion cas­cades”, where an ini­tial species loss leads to a domino effect of fur­ther extinctions.

The researchers, from the Uni­ver­sity of Exeter, showed there is a higher risk of extinc­tion cas­cades when other species are not present to fill the “gap” cre­ated by the loss of a species.

Even if the loss of one species does not directly cause knock-​on extinc­tions, the study shows that this leads to sim­pler eco­log­i­cal com­mu­ni­ties that are at greater risk of “run-​away extinc­tion cas­cades” with the poten­tial loss of many species. The study is pub­lished ahead of print on 21 Feb­ru­ary in the jour­nal Pro­ceed­ings of the National Acad­emy of Sci­ences.

With extinc­tion rates at their high­est lev­els ever and numer­ous species under threat due to human activ­ity, the find­ings are a fur­ther warn­ing about the con­se­quences of erod­ing biodiversity.

Inter­ac­tions between species are impor­tant for ecosys­tem sta­bil­ity,” said Dr Dirk Sanders, of the Cen­tre for Ecol­ogy and Con­ser­va­tion at the Uni­ver­sity of Exeter. “And because species are inter­con­nected through mul­ti­ple inter­ac­tions, an impact on one species can affect oth­ers as well.

Our results demon­strate that bio­di­ver­sity loss can increase the vul­ner­a­bil­ity of ecosys­tems to sec­ondary extinc­tions which, when they occur, can then lead to fur­ther sim­pli­fi­ca­tion caus­ing run-​away extinc­tion cascades.

Dr Dirk Sanders, lead author, Cen­tre for Ecol­ogy & Con­ser­va­tion and Envi­ron­ment and Sus­tain­abil­ity Insti­tute, Col­lege of Life and Envi­ron­men­tal Sci­ences, Uni­ver­sity of Exeter, Corn­wall, United Kingdom

It has been pre­dicted that more com­plex food webs will be less vul­ner­a­ble to extinc­tion cas­cades because there is a greater chance that other species can step in and buffer against the effects of species loss,” Sanders added.

In our exper­i­ment, we used com­mu­ni­ties of plants and insects to test this prediction.”

The researchers removed one species of wasp and found that it led to sec­ondary extinc­tions of other, indi­rectly linked, species at the same level of the food web. This effect was much stronger in sim­ple com­mu­ni­ties than for the same species within a more com­plex food web.

How extinc­tion cas­cades work
The loss of a preda­tor can ini­ti­ate a cas­cade, such as in the case of wolves, where their extinc­tion on one moun­tain can cause a large rise in the num­ber of deer. This larger num­ber of deer then eats more plant mate­r­ial than they would have before. This reduc­tion in veg­e­ta­tion can cause extinc­tions in any species that also relies on the plants, but are poten­tially less com­pet­i­tive, such as rab­bits or insects.

(Source: Uni­ver­sity of Exeter new release, 19.02.2018)

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