Can selective logging maintain forest biodiversity?

Friday, 1 August 2014

Taking just a few large trees per hectare of tropical forest will see a substantial reduction in biodiversity with the biggest impact on mammals and amphibians, a new study has found.

Published today in the journal Current Biology, the team of Australian, Swiss and United States scientists have quantified the impacts of logging at various intensities on different groups of animals found in tropical forests. They have established thresholds of logging intensity beyond which species are lost to the forest.

They found that mammals and amphibians were most sensitive to logging. The number of species in these groups would be halved at logging intensities of just 38 m3 per hectare (removing about 3-4 large trees from every hectare) and 63 m3 per hectare (about 6-7 large trees) respectively.

"Selective logging is becoming increasingly common throughout the world's tropical forests," says co-author Associate Professor Lian Pin Koh, from the University of Adelaide's Environment Institute.

"While the effects of deforestation are pretty clear, the impact of selective logging on forest biodiversity is still poorly understood and, most likely, commonly underestimated."

Associate Professor Koh, who is a new Australian Research Council Future Fellow with the University of Adelaide, and colleagues PhD student Zuzana Burivalova from ETH Zurich and Dr Çağan Şekercioğlu from the University of Utah, analysed data from 48 published studies to quantify the impact of various logging intensities on mammals, amphibians, invertebrates and birds.

They found that most groups of animals were resilient under logging intensities of 10 m3 per hectare (about one large tree a hectare) or less. Above this intensity biodiversity was reduced, with the level of impact dependent on the type of animal and location of the forest.

Birds show an opposite trend with the number of species increasing with logging intensity. However this is largely due to an influx of other species while the numbers of original forest species decline.

"Tropical forests around the world are being lost at an alarming rate and the remaining forest is being degraded by selective logging," says Associate Professor Koh.

"At the extreme end of the range, forest concessions in Borneo are logged at very high intensities of up to 15-20 trees per hectare.

"We hope our findings will help policymakers in the timber producing countries develop more sustainable logging practices to reduce the impacts on biodiversity."

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