Thresholds for adding degraded tropical forest to the conservation estate
Robert M. Ewers, C. David L. Orme, William D. Pearse, Nursyamin Zulkifli, Genevieve Yvon‐Durocher, Kalsum M. Yusah, Natalie Yoh, Darren C. J. Yeo, Anna Wong, Joseph R. Williamson, Clare L. Wilkinson, Fabienne Wiederkehr, Bruce L. Webber, Oliver R. Wearn, Leona Wai, Maisie Vollans, Joshua P. Twining, Edgar C. Turner, Joseph A. Tobias, Jack Thorley, Elizabeth Telford, Yit Arn Teh, Heok Hui Tan, Tom Swinfield, Martin Svátek, Matthew J. Struebig, Nigel E. Stork, Jani Sleutel, Eleanor M. Slade, Adam Sharp, Adi Shabrani, Sarab S. Sethi, Dave J. I. Seaman, Anati Sawang, Gabrielle Roxby, J. Marcus Rowcliffe, Stephen J. Rossiter, Terhi Riutta, Homathevi Rahman, Lan Qie, Elizabeth Psomas, Aaron Prairie, Frederica Poznansky, Rajeev Pillay, Lorenzo Picinali, Annabel Pianzin, Marion Pfeifer, Jonathan M. Parrett, Ciar Noble, Reuben Nilus, Nazirah Mustaffa, Katherine E. Mullin, Simon L. Mitchell, Amelia McKinlay, Sarah C. Maunsell, Radim Matula, Mike R. Massam, Stephanie Martin, Yadvinder Malhi, Noreen Majalap, Catherine S. Maclean, Emma Mackintosh, Sarah H. Luke, Owen T. Lewis, Harry J. Layfield, Isolde Lane-Shaw, Boon Hee Kueh, Pavel Kratina, Oliver Konopik, R. L. Kitching, Lois Kinneen, Victoria Kemp, Palasiah Jotan, Nick S. Jones, Evyen Wevan Jebrail, Michal Hroneš, Sui Peng Heon, David Hemprich‐Bennett, Jessica K. Haysom, Martina F. Harianja, Jane Hardwick, Nichar Gregory, Ryan Gray, Ross Gray, Natasha R. Granville, Richard J. Gill, Adam Fraser, William A. Foster, Hollie Folkard‐Tapp, Robert J. Fletcher, Arman Hadi Fikri, Tom M. Fayle, Aisyah Faruk, Paul Eggleton, David P. Edwards, Rosie Drinkwater, Rory A. Dow, Timm F. Döbert, Raphaël K. Didham, Katharine J. M. Dickinson
Abstract
Abstract Logged and disturbed forests are often viewed as degraded and depauperate environments compared with primary forest. However, they are dynamic ecosystems 1 that provide refugia for large amounts of biodiversity 2,3 , so we cannot afford to underestimate their conservation value 4 . Here we present empirically defined thresholds for categorizing the conservation value of logged forests, using one of the most comprehensive assessments of taxon responses to habitat degradation in any tropical forest environment. We analysed the impact of logging intensity on the individual occurrence patterns of 1,681 taxa belonging to 86 taxonomic orders and 126 functional groups in Sabah, Malaysia. Our results demonstrate the existence of two conservation-relevant thresholds. First, lightly logged forests (<29% biomass removal) retain high conservation value and a largely intact functional composition, and are therefore likely to recover their pre-logging values if allowed to undergo natural regeneration. Second, the most extreme impacts occur in heavily degraded forests with more than two-thirds (>68%) of their biomass removed, and these are likely to require more expensive measures to recover their biodiversity value. Overall, our data confirm that primary forests are irreplaceable 5 , but they also reinforce the message that logged forests retain considerable conservation value that should not be overlooked.