Forest Fragmentation Causing Mammal Species To Die Off Faster Than Expected

By Philip Ross on September 26, 2013 5:20 PM EDT

forest fragmentation
Forest fragmentation is killing off mammal populations much faster than scientists expected. (Photo: Creative Commons)

As rainforests become increasingly splintered, mammals are going extinct much faster than previously expected. Scientists tracking native small mammals in the Chiew Larn Reservoir in Thailand, which was filled in 1986 and 1987 and created more than 100 islands, found that the isolation of the small, fragmented landmasses is causing mammal populations in that area to decline at an alarming rate.

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A new study published in the journal Science argues that an ecological "Armageddon" is taking place in areas where forest fragmentation has occurred. According to the findings, it took just two decades for native small mammals in Thailand's hydroelectric reservoir to become nearly extinct.

"Tropical forests remain one of the last great bastions of biodiversity, but they continue to be felled and fragmented into small 'islands' around the world," said professor Corey Bradshaw, Director Ecological Modelling at the University of Adelaide's Environment Institute and co-author of the study, according to Phys.org. "This study shows we need to be even more concerned than we thought - the speed at which there was near-total loss of native small mammals was alarming and shows that leaving fragments of forest behind is not nearly enough to protect these species."

Monga Bay reports that Bradshaw and the rest of the team repeated a number of surveys from the early 1990s of small mammals on 12 of the islands. The islands ranged in size from .3 to 56.3 hectares, or about .7 to 140 acres.

The surveys from 20 years ago found that after 5 to 7 years of isolation, the three biggest islands still had sizeable populations of seven to 12 species of mice, squirrels, shrews and rats - similar to the density of small mammal species in the forests of the nearby mainland. But the story wasn't the same for the smaller islands. There, researchers discovered just one to three of those species on each plot of land.

After doing the same surveys again in 2012 and 2013, researchers found that a number of the animals had disappeared. According to Science Mag, of the 47 common tree shrews found in 1993, just one popped up in 2013.

"This study makes a valuable contribution in quantifying how fast the extinctions take place-very fast in this case," Ilkka Hanski, an ecologist at the University of Helsinki, told Science Mag.

According to National Geographic, at the current rate of deforestation, Earth's rainforests could completely vanish in a hundred years. The number one cause of deforestation is agriculture. Large swaths of trees are cut down to make room for crops and livestock.

The greatest threat deforestation poses is to the millions of species that live in them. More than 70 percent of Earth's land animals and plants live in forests. Cutting down trees, whether for industry, fuel or agriculture, leads to their extinction.

Read more from iScience Times:

Alaska Glacier Thaws: Astonishing Ancient Forest Revealed As Global Warming Debate Continues [REPORT]

Global Warming May Lead To Mass Extinction Of Viviparous Lizards

Brazil's Rainforest Suffering Widespread Extinction

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