Variable responses of individual species to tropical forest degradation

The functional stability of ecosystems depends greatly on interspecific differences in responses to environmental perturbation. However, responses to perturbation are not necessarily invariant among populations of the same species, so intraspecific variation in responses might also contribute. Such inter-population response diversity has recently been shown to occur spatially across species ranges, but we lack estimates of the extent to which individual populations across an entire community might have perturbation responses that vary through time. We assess this using 524 taxa that have been repeatedly surveyed for the effects of tropical forest logging at a focal landscape in Sabah, Malaysia. Just 39 % of taxa – all with non-significant responses to forest degradation – had invariant responses. All other taxa (61 %) showed significantly different responses to the same forest degradation gradient across surveys, with 6 % of taxa responding to forest degradation in opposite directions across multiple surveys. Individual surveys had low power (< 80 %) to determine the correct direction of response to forest degradation for one-fifth of all taxa. Recurrent rounds of logging disturbance increased the prevalence of intra-population response diversity, while uncontrollable environmental variation and/or turnover of intraspecific phenotypes generated variable responses in at least 44 % of taxa. Our results show that the responses of individual species to local environmental perturbations are remarkably flexible, likely providing an unrealised boost to the stability of disturbed habitats such as logged tropical forests

Thresholds for adding degraded tropical forest to the conservation estate.

Acknowledgements: This study was supported by funding to the Stability of Altered Forest Ecosystems Project by the Sime Darby Foundation. Research permission and site access were provided by the Maliau Basin Management Committee, the Sabah Foundation, Benta Wawasan, Sabah Softwoods, the Innoprise Foundation, the Sabah Forestry Department and the Sabah Biodiversity Centre. R.M.E. is supported by the NOMIS Foundation. Data collection was financed by Australian Research Council grant DP140101541; Bat Conservation International; the British Council Newton-Ungku Omar Fund 216433953; British Ecological Society grant 3256/4035; the Cambridge Trust; the Cambridge University Commonwealth Fund; the Czech Science Foundation (14-32302S); the European Research Council (281986); the European Social Fund and the Czech Republic (CZ.1.07/2.3.00/20.0064); the Fundamental Research Grant Scheme (FRG0302-STWN-1/ 2011), Ministry of Higher Education, Malaysia; FFWS CZU (IGA number A_26_22); the Jardine Foundation; Malaysia Industry Group for High Technology (216433953); the Ministry of Education, Youth and Sports of the Czech Republic (INTER-TRANSFER LTT19018); the Panton Trust; the Primate Society of Great Britain; ProForest; Royal Society of London grant RG130793; the Sime Darby Foundation; the S. T. Lee Fund; the Sir Philip Reckitt Educational Trust; the Tim Whitmore Fund; the Universiti Malaysia Sabah; the University of East Anglia; the University of Kent; the University of Florida Institute of Food and Agricultural Sciences; UK Research and Innovation Natural Environment Research Council grants NE/H011307/1, NE/K016253/1, NE/K016407/1, NE/K016148/1, NE/K0106261/1, NE/K015377/1, NE/L002515/1, NE/L002582/1 and NE/P00363X/1 and studentship 1122589; the Varley Gradwell Travelling Fellowship; and the World Wildlife Fund for Nature. Data collection was supported by R. Adzhar, A. Afendy, N. Arumugam, S. Benedick, V. Bignet, S. Butler, K. Graves, H. E. Hah, H. Heroin, A. Kendall, H. H. Mahsol, D. Mann, J. Miller, S. Milne, J. Mumford, D. Norman, H. Rossleykho, D. Shapiro, K. Sieving, J. Sugau, B. Udell, B. E. Yahya and M. A. Zakaria.Logged and disturbed forests are often viewed as degraded and depauperate environments compared with primary forest. However, they are dynamic ecosystems1 that provide refugia for large amounts of biodiversity2,3, so we cannot afford to underestimate their conservation value4. 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 (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 irreplaceable5, but they also reinforce the message that logged forests retain considerable conservation value that should not be overlooked