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 tangible - water moves downhill or over floodplains, or more subtle - terrestrial organic matter is incorporated into aquatic food webs. Animals and people naturally gravitate to freshwaters, thus providing additional dispersal vectors that can carry propagules to isolated sites. Connectivity may be passive or active and occurs across scales from the local to the 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. However, in reality, a long tradition of focusing on individual stressors, sites, taxonomic groups or habitats, has led to a highly disjointed view of the most intrinsically interconnected resource on the planet. While the need for an integrated approach to water management is universally acknowledged, an understanding of this most fundamental part of the infrastructure of freshwaters is lacking. This is a serious obstacle to meeting critical societal challenges, namely the maintenance of environmental sustainability in the face of multiplying human-induced stresses. Without a more integrated view of the freshwater landscape we struggle to answer basic questions. These include (i) how do organisms, nutrients and energy move naturally within and between landscapes? (ii) how is this basic template altered by different stressors, singly or in combination? (iii) how has widespread alteration of land cover and of the basic infrastructure of freshwaters that largely drives connectivity, redistributed pressures and modified their effects? (iv) how should reductions in stressors and changes to connectivity, that are now widely implemented, be prioritised when seeking to restore biodiversity and ecosystem function?Our primary aims are to (1) determine how hydrological, spatial and biological connectivity impact 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 vs national) and temporal (sub-annual to decadal vs centennial) scales and using a combination of complementary well established 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 targeted sampling to maximise cost effectiveness 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 needed to ensure resilience to climate change and to underpin large scale conservation and restoration of aquatic landscapes is currently lacking. In this regard an understanding of 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 required urgently.