Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon Land-use change is associated with a significant loss of freshwater fish species and functional richness in Sabah, Malaysia Clare L. Wilkinson a,b,c, ⁎ , Darren C.J. Yeo b , Tan Heok Hui c , Arman Hadi Fikri d , Robert M. Ewers a a Department of Life Sciences, Imperial College London, Silwood Park, Silwood Park, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK b Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Republic of Singapore c Lee Kong Chian Natural History Museum, National University of Singapore, 2 Conservatory Drive, Singapore 117377, Republic of Singapore d Institute of Tropical Biology & Conservation, Universiti Malaysia Sabah, Malaysia ARTICLE INFO Keywords: Deforestation Freshwater fish Land-use change Oil-palm Southeast Asia ABSTRACT Global biodiversity is being lost due to extensive anthropogenic land cover change. In Southeast Asia, biodi- versity-rich forests are being extensively logged and converted to oil-palm monocultures. The impacts of this land-use change on freshwater ecosystems, and particularly on freshwater biodiversity, remain largely under- studied and poorly understood. We assessed the differences between fish communities in headwater stream catchments across an established land-use gradient in Sabah, Malaysia (protected forest areas, twice-logged forest, salvage-logged forest, oil-palm plantations with riparian reserves, and oil-palm plantations without ri- parian reserves). Stream fishes were sampled using an electrofisher, a cast net and a tray net in 100 m long transects in 23 streams in 2017. Local species richness and functional richness were both significantly reduced with any land-use change from protected forest areas, but further increases in land-use intensity had no sub- sequent impacts on fish biomass, functional evenness, and functional divergence. Any form of logging or land- use change had a clear and negative impact on fish communities, but the magnitude of that effect was not influenced by logging severity or time since logging on any fish community metric, suggesting that just two rounds of selective impact (i.e., logging) appeared sufficient to cause negative effects on freshwater ecosystems. It is therefore essential to continue protecting primary forested areas to maintain freshwater diversity, as well as to explore strategies to protect freshwater ecosystems during logging, deforestation, and conversion to plantation monocultures that are expected to continue across Southeast Asia. 1. Introduction Anthropogenic land cover change through agricultural expansion and intensification is currently a major driver of global biodiversity loss (MEA, 2005; Phalan et al., 2013). The destruction of tropical forests is of particular significance owing to the disproportionately high levels of biodiversity present in the tropics (Bradshaw et al., 2009; Laurance et al., 2012), marked declines in biodiversity when tropical forest is converted to other land-use types (Phalan et al., 2013), and the una- bated levels of deforestation due to increasing human demands for food, timber and other products (Sodhi et al., 2004; Wilcove et al., 2013). Large areas of logged forest and agriculture will be key features of future tropical landscapes. Primary forests are critically important for conserving tropical biodiversity (Gibson et al., 2011) and once-logged forests in Southeast Asia have high conservation value for terrestrial taxa (Edwards et al., 2014), but focussing on these habitats alone is not sufficient. The impacts of this large scale land-use change and other anthropogenic activities on freshwater ecosystems and biodiversity in tropical streams remains largely understudied and poorly understood (Ramirez et al., 2008). It is important to understand how these chan- ging landscapes impact upon aquatic as well as terrestrial biodiversity, and to devise strategies that provide protection mechanisms. The most widespread and destructive threat to aquatic ecosystems is habitat modification that results from converting natural areas to agricultural land (Allan and Flecker, 1993; Laurance et al., 2014). Ex- tensive logging and deforestation across the tropics (Achard et al., 2002; Hansen et al., 2010) has caused large scale modifications to catchments, resulting in changes in water quantity, quality, de-regula- tion in stream hydraulics and increased sedimentation levels (Inoue and Nunokawa, 2005; Iwata et al., 2003). The effects of deforestation on the species richness of fish are variable. Species richness can be increased (Lorion and Kennedy, 2009), decreased (Brook et al., 2003; Toham and Teugels, 1999), or unaffected (Bojsen and Barriga, 2002) by tropical deforestation, with equally variable impacts on fish community https://doi.org/10.1016/j.biocon.2018.04.004 Received 27 November 2017; Received in revised form 22 March 2018; Accepted 2 April 2018 ⁎ Corresponding author at: Imperial College London, Silwood Park, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK. E-mail address: clare.wilkinson12@imperial.ac.uk (C.L. Wilkinson). Biological Conservation 222 (2018) 164–171 0006-3207/ © 2018 Elsevier Ltd. All rights reserved. T