Why does it matter that Missouri’s forest land is becoming increasingly fragmented and degraded? Because forest land provides essential ecological services. This “Noah’s Ark” function is lost when forest becomes fragmented and degraded.

Google Earth Screenshot of some of the Chiew Lan Islands in the study. The largest is 1 mile in length, considerably larger than many Missouri forest tracts.

A recent study illustrated this effect. A new dam was constructed in Thailand in 1987. The reservoir behind it filled a valley, turning a number of high points into islands surrounded by water. Scientists were able to study what happened to the animals left on them.

(Click on map for larger view.)

In less than 14 years half of the small mammal species had vanished, and within 25 years, the only small mammals that the scientists found on the islands were rats that had not been there when the islands were formed.

Many factors cause losses like these. Isolated groups of animals accumulate harmful mutations. The habitat itself changes, making it unable to support the life it once did. And the small, cut off islands are vulnerable to invasion by a non-native but very aggressive species, like rats.

Now, this study occurred in Thailand. Some of Missouri’s fragmented and degraded forest tracts are even smaller than the islands in this study, but some are not. Some are as thoroughly isolated as the islands in this study, but some are not. The effect may not be as drastic here, or it may not occur as quickly. But it certainly exists.

The study in Thailand is a stark illustration of why forest fragmentation and degradation is a problem.

Source:

Gibson, Luke, Antony Lynam, Corey Bradshow, He Fangliang, David Bickford, David Woodruff, Sara Bumrungsri, and William Laurance. (2013). Near-Complete Extinction of Native Small Mammal Fauna 25 Years After Forest Fragmentation. Science, 341, (6153), 1508-1510.