Turning back the tide? Local-scale impacts of climate change may have positive effects by restoring natural riverine habitat and reducing invasive fish density

Global biodiversity is increasingly threatened by habitat loss, climate change, and biological invasion. However, predictions of impacts on native fauna are hampered by an inadequate knowledge of how these factors interact and how climate change will affect the distribution, abundance, and behaviour of both native and invasive species, not least as most predictions are based on the long-term effects of temperature alone. Here, we present a case study illustrating how local-scale climate change impacts (increased temperature, reduced rainfall, shifts in peak rainfall) affected the hydrology of a channelised lowland European river (reduced flow, reduction in flood events, increased siltation, macrophyte growth), allowing native fish species to recolonise the bankside zone and reducing the density of invasive round gobyNeogobius melanostomusby removing its preferred habitat. While most studies predict long-term negative impacts on global fish populations, some suggest potential direct and indirect benefits at a local scale. We are of the opinion that, at a local scale, climate change impacts on fish will be more nuanced and complex than long-term predictions suggest, resulting in both positive and negative effects, withconsolation prizesin the face of larger losses. While impacts on fish will differ between regions and/or continents, depending on the specific impacts of climate change, identification of positive effects will be essential in clarifying long-range forecasts and identifying management procedures for mitigating overall negative impacts.