Tropical forests may be hiding mass extinctions


Species loss from disturbed tropical habitats will be much higher than previously thought, a new study says. Andrew Masterson reports


Fires burn off logged virgin rainforest, home to threatened orangutans and other rare species of wildlife in Tripa, Aceh province, Indonesia. Scientists warn deforestation could lead to 'hundreds of thousands' more extinctions in the near future.
Robert Nickelsberg / getty images

A mass extinction of tropical species ranging from bats to butterflies may have already happened without anyone noticing, suggests research from Australia’s Macquarie University.

In a paper published in the journal Proceedings of the National Academy of Sciences, biologist John Alroy has used local-scale ecological data obtained across the world’s tropical zones to predict global-scale extinction rates across 11 key ecological groups.

The results predict the extinction of more than 28% species in seven of those groups given complete disturbance of tropical forests. Only two animal groups – large mammals and mosquitoes – would lose less than 18% of species.


The data analysis – by far the largest and most comprehensive ever undertaken – suggests a scale of loss much higher than previously thought. Alroy warns continuing deforestation could therefore lead to the extinction of “hundreds of thousands” of species.

“The overall implication of this research is that any substantial loss of primary forests will result in numerous extinctions across many groups,” he says.

“There are a lot of reasons to think these results are conservative, so the real effects are likely to be even greater. Even if we preserve forests of some kind in many places, unless we protect them from ever being logged, those forests may end up being empty.”

Alroy suggests a high number of vulnerable and endangered species might have already vanished, their disappearance masked by the spread of more common species better able to tolerate habitat disturbance.

“A mass extinction could have happened right under our noses because we just don't know much about the many rare species that are most vulnerable to extinction,” he says.

“To figure out whether this is true, a lot more field work needs to be done in the tropics. The time to do it is now.”

Roughly two-thirds of the world’s animal species are found in tropical forest areas. The forests themselves occupy only about 10% of the planet’s land surface, making them – and their inhabitants – particularly vulnerable to disturbance.

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Andrew Masterson is news editor of Cosmos.
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