Study: Loss of threatened vertebrates may lead to drop in functional diversity


Loss of species that play a unique role in the environment could have dramatic effects on the global ecosystem, a new study has found. Photo by Ken Bohn/San Diego Zoo
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Aug. 27 (UPI) -- Loss of species currently identified as threatened with extinction by the International Union for the Conservation of Nature could cause up to a 30% decline in their functional diversity in some parts of the world, according to a study published Friday.

The study, published in the journal Nature Communications, found the loss of functional diversity -- which refers to population levels needed for living organisms to perform their essential roles in the environment -- could be particularly severe for five groups of vertebrates, including birds, mammals, reptiles, amphibians and freshwater fish.

For example, parts of South and Southeast Asia would be the most impacted by the loss of threatened species for mammals and birds, with an up to 20% decrease of functional diversity, the researchers said.

Meanwhile regions of northern Europe, Asia and north Africa would be the most affected by loss of reptiles, amphibians and freshwater fish, with as much as a 30% drop in functional diversity, according to the researchers.

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"Loss [of these species] would strongly imperil those fragile ecosystems," study co-author Aurele Toussaint said in a press release.

"This highlights the need for action required for the biodiversity conservation in Asia," said Toussaint, a research fellow at the University of Tartu in Estonia.

The number of vertebrate species inhabiting the different regions of the world, and those that are threatened, varies, according to Toussaint and his colleagues.

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However, the loss of species refers not only to their respective populations but also on their ecological role, the researchers said.

These roles depend on the characteristics of the species, such as size, weight, shape and reproductive capacity, as well as the food resource they use.

If threatened species have similar characteristics to non-threatened species, their loss due to extinction may be counterbalanced by other species, according to the researchers.

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Conversely, if threatened species have unique characteristics, their loss can have a dramatic effect on the functioning of ecosystems and the services they provide to human well-being.

To understand how the different regions across the world could be functionally impacted by the loss of threatened vertebrates, researchers compiled data on the characteristics of roughly 50,000 vertebrate species -- about 70% of all vertebrates globally -- and their populations.

Then, the researchers assessed whether the loss of threatened species will have similar consequences on the functional diversity in six regions worldwide.

The loss of threatened species will have similar consequences across the world, but with different intensities, according to the researchers.

For mammals, loss in functional diversity is mainly linked with the extinction of primate species such as chimpanzees, bonobos and gorillas in Africa or orangutans in Asia, as well as spider monkeys and capuchin monkeys in the tropics.

With birds, any loss of functional diversity in southern Asia would be fueled by population drops of the White-shouldered ibis or the Indian vulture, both of which are close to extinction, mainly due to habitat loss and degradation.

Many large-bodied freshwater fish, such as sturgeons, are threatened in the upper northern hemisphere, while many small-bodied species, such as catfish, are threatened in the global south.

As these species have different levels of functional uniqueness in terms of their roles in the ecosystem, global measures to protect them need to be adapted to each region, the researchers said.

Currently, most conservation plans target species diversity, under the assumption that this approach protects biodiversity.

For example, there are around 300 amphibian species in northern Europe and Asia and more than 1,000 species in tropics, Toussaint said.

Because the amphibian species in the north have more unique functional traits than those in the south, their loss would have a more significant effect on functional diversity, he said.

"Conservation strategies should ... go beyond the sole number of species and target the species with a unique ecological role," Toussaint said.