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Forest loss in tropical catchments has mixed impacts on stream food webs
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  • Jia Huan Liew,
  • Kenny WJ Chua,
  • Clare Wilkinson,
  • Heok Hui Tan,
  • Keith Martin-Smith,
  • Ahmad Amirrudin,
  • David Dudgeon,
  • Darren Yeo
Jia Huan Liew
University of Hong Kong
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Kenny WJ Chua
National University of Singapore
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Clare Wilkinson
Imperial College London
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Heok Hui Tan
National University of Singapore
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Keith Martin-Smith
Hutchins School
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Ahmad Amirrudin
Universiti Malaysia Terengganu
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David Dudgeon
University of Hong Kong
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Darren Yeo
National University of Singapore
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Abstract

Forest loss is a major environmental threat in the Anthropocene. Repercussions are rarely localised and often impacts adjacent ecosystems. For example, forest loss is generally detrimental to freshwater biodiversity. There are however, some uncertainties about its effects on food webs and ecosystem functioning. We tracked changes in the food webs of four tropical stream catchments (two time points separated by a ~20-year interval) affected by varying degrees of forest loss. Our data show that the proportion of assimilated terrestrial organic matter (allochthony) remained largely invariant, but changes in food chain lengths inferred from the trophic positions of apex predators (TP) differed between catchments. Here, we found that higher rates of forest loss resulted in more significant reductions in TP. We speculate that the mechanisms involved are unrelated to diminished terrestrial subsidies as allochthony values were low (~7%) and did not shift in response to forest loss.