Hydroscape:connectivity x stressor interactions in freshwater habitats

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All types of ecosystems exhibit connectivity at some level. However, connectivity is the quintessential property of aquatic systems. Connectivity matters in freshwaters because it is the means by which energy, materials, organisms and genetic resources move within and between hydrological units of the landscape (the 'hydroscape'). Hydrological connectivity is a particularly effective vector for multiple climatic, biological, chemical and physical stressors, although other forms of connectivity also link freshwater ecosystems. Our proposal addresses the fundamental question of how connectivity and stressors interact to determine biodiversity and ecosystem function in freshwaters.Connectivity is multifaceted. It may be directly evident - water moves downhill or across floodplains, or more subtle - the incorporation of terrestrial organic matter into aquatic food webs. Animals and people naturally gravitate to freshwaters, thus providing additional dispersal vectors that can transport propagules to isolated sites. Connectivity may be passive or active and occurs across scales - from local to global. Freshwater scientists recognise the fundamental role of connectivity in key paradigms such as the river continuum and flood pulse concepts. Land-water connectivity is also the founding principle behind catchment management. In truth, however, a long tradition of focus on individual stressors, sites, taxonomic groups or specific habitats, means we have a highly disjointed view of the most intrinsically interconnected resource on the planet. While the need for an integrated approach to the management of water is universally acknowledged, an understanding of the most fundamental infrastructure of freshwaters is lacking. This is a serious obstacle in meeting critical societal challenges, namely the maintenance of environmental sustainability in the face of multiplying human-induced stresses. Without a better-integrated view of the freshwater landscape we struggle to answer basic questions. These include (i) how do organisms, nutrients and energy naturally move within and between landscapes? (ii) how is this basic template altered by different stressors, singly or in combination? (iii) how has widespread alteration of catchment land cover and of the basic infrastructure of freshwaters that largely drives connectivity, redistributed pressures and moderated their effects? (iv) how should reductions in stressors and changes to connectivity that arenow widely implemented, be prioritised when seeking to restore biodiversity and ecosystem function.Our primary aims are to (1) determine how connectivity (hydrological, spatial and biological) impacts on freshwater ecosystem structure and function in contrasting landscape types, and (2) use this understanding to forecast how freshwaters nationally will respond to (i) multiple, interacting pressures and (ii) management actions designed to reduce pressures and/or alter connectivity. We will achieve these aims by working at different spatial (landscape v national) and temporal (decadal v centennial) scales and using a combination of complementary traditional and more novel molecular and stable isotope techniques. We will combine existing data sources (e.g. archived sediment cores, biological surveys and the millions of records held in national databases) with dedicated sampling to maximise the cost effectiveness of our work and achieve a cross habitat and ecosystem-wide reach. Landscape scale thinking has become the new mantra of nature conservation and environmental bodies but the knowledge required to underpin large scale conservation and restoration of the hydroscape is currently lacking. In this regard understanding how biodiversity and ecosystem function respond to the changing connectivity x stressors arena in freshwaters is critical. The outputs of the proposed research will deliver the integrated understanding of the hydroscape that is now urgently required.