Tropical biodiversity study finds no substitute for primary forests

​Undisturbed primary forests are irreplaceable for sustaining tropical biodiversity, according to a study published in Nature (14 September).

Primary tropical forests with little or no human disturbance are diminishing due to conversion and degradation by human activities and in many locations they have been replaced by agriculture, plantations and secondary forests.

But an international team of researchers, including Dr Jos Barlow of Lancaster University, has concluded that most forms of forest degradation have an overwhelmingly detrimental effect on tropical biodiversity, and secondary forests are poor substitutes for primary forests.

The team of researchers from the National University of Singapore (NUS), University of California, San Diego (UCSD), ETH Zurich, University of Adelaide, University of Cambridge, Lancaster University, University of East Anglia, James Cook University and the Heinz Center for Science, Economics and the Environment conducted a global assessment to estimate the impact of disturbance and land conversion on biodiversity in tropical forests.

Drawing on information from 138 scientific studies spanning 28 tropical countries, they compared biodiversity values between primary forests and a range of degraded and converted forest types including secondary forests, selectively logged forests and forests converted to agriculture. Overall, biodiversity values were substantially lower in degraded forest types, highlighting the strong impact human land-use changes are exacting on tropical biodiversity.

“There’s no substitute for primary forests,” said Luke Gibson, the lead author who is a PhD student in the Department of Biological Sciences (DBS) at NUS. “Our comprehensive assessment shows that all major forms of disturbance – with one possible exception – invariably reduce biodiversity in tropical forests.”

That exception is selective logging, which had a relatively small – but still negative – impact on biodiversity. “Ecological restoration of selectively logged forests might represent an effective strategy to alleviate threats to tropical biodiversity, particularly when they are also rapidly growing in extent,” said Lian Pin Koh, an adjunct professor at NUS DBS and an assistant professor of Applied Ecology and Conservation at ETH Zurich.

Comparing human impacts across the key tropical forested regions, the authors found that Asia suffered the greatest loss in biodiversity but  said there was an the urgent need for more research in understudied regions, particularly in Africa, which sustains the second largest contiguous tropical forest in the world.

To protect the world’s remaining primary tropical forests, the study suggests a number of strategies, including the expansion and enhanced enforcement of protected areas. Curbing international demand for commodities obtained at the expense of primary forests is another strategy to protect tropical biodiversity.

Primary forests are irreplaceable for sustaining tropical biodiversity was published in Nature by Luke Gibson, Tien Ming Lee, Lian Pin Koh, Barry W. Brook, Toby A. Gardner, Jos Barlow, Carlos A. Peres, Corey J. A. Bradshaw, William F. Laurance, Thomas E. Lovejoy & Navjot S. Sodhi. Primary forests are irreplaceable for sustaining tropical biodiversity.  Available at www.nature.com/nature.

ENDS