Fragility of stream ecosystem functioning in response to drought: an experimental test

Climate change and human activities are expected to change the quantity of water entering rivers and streams, with potentially dramatic impacts on animals and plants resident in these ecosystems. In many regions, climate change is expected to reduce rainfall and bring about drought conditions, and water abstraction and river diversions may also reduce flows in rivers and streams. To date, relatively little work has been done to determine the effect of hydrologic droughts on aquatic biodiversity, and less is known about impacts on important processes, such as decomposition and nutrient cycling, that affect water quality and productivity of aquatic life.

Our study will use novel experiments to understand the ecological effects of hydrologic droughts in streams, with a view to predicting future change. We will use a series of artificial stream channels to directly manipulate flows, thereby simulating drought episodes, and measure the responses of flora and fauna, and a series of processes that reflect the ecological health of the ecosystem. We will establish a series of experimental drought treatments which differ in the extent of flow reduction, from unaltered reference conditions to extreme low flows that cause habitat loss. We will also examine how the physical nature of the stream bed affects the extent to which animals and plants can withstand periods of drought, and how quickly these communities recover from these events. With a project student, we will investigate how water abstraction, a leading anthropogenic cause of stream drought, affects biodiversity and functioning across a suite of lowland streams in south west England. Together, the results will give valuable insights into the ways in which the environment responds to change brought about through human activities and the likely effects of climate change.

Who will benefit from this research?

The main non-academic beneficiaries of knowledge arising from this research will be regulatory authorities (e.g. Environmental Agency of England and Wales, Natural England) and water companies (e.g. Wessex Water plc) who will be able to use outputs to inform policies of water resource management at the catchment scale. Governmental authorities determine water abstraction from rivers and groundwaters and river diversions that affect flows via regulatory policies (licensing) and catchment management planning. A clearer understanding of the link between river flows and ecological impacts is required to drive cost effective policies that have a demonstrable positive influence on measured ecological quality under the EU Water Framework Directive (WFD). Other potential beneficiaries include JNCC and associated organisations (e.g. Natural England) that are responsible for management of sites for conservation, and government-funded research centres (e.g. colleagues at Centre for Ecology and Hydrology, National Centre of Environment and Energy and Aarhus University - Denmark, CSIRO - Australia) advising on the implementation of environmental legislation. The management of river flows in catchments containing designated sites (e.g. SSSIs, SACs) may be necessary for sites to be maintained in favourable condition. This project will identify the extent to which drought conditions affect running waters and will identify key community and functional indicators of low flow stress.

Our research is based on lowland streams, which have long been the subject of intense public interest as protected areas with high biodiversity and amenity value. As part of our current work with the EA in Hampshire (Dr Shirley Medgett, Technical Specialist) on effects of low flow and high nutrient loads on lowland rivers, we have engaged with the following stakeholders: Wessex Water plc (Fiona Bowles), The Test and Itchen Association (Technical Director Tom Davis), Game Conservancy (Bill Beaumont) and Wessex Chalk Stream and Rivers Trust (Mr Tom Davis), Vitacress Conservation Trust (Dr Steve Rothwell) and Upper Itchen Initiative (Graham Roberts). As part of the proposed research, we will seek to develop and extend knowledge exchange with such groups.

How will they benefit?

We will engage with these diverse groups via the following activities (see Pathways to Impact):

-Establishment of an Advisory Group from the outset to involve beneficiaries directly in the research and maximise the impact of the science. Representatives of national and international organisations have agreed to contribute (see letters of support and Pathways to Impact) including: project partners Freshwater Biological Association, Aarhus University Denmark, Natural England and Wessex Water plc.

-A network of academics and non-academic beneficiaries will be established and two workshops held to review the current evidence base for low flow stressors and to develop collaborative projects that bridge the gap between freshwater science and water resource management.

-Placements have been arranged for each PDRA with our project partner Natural England (Dr Chris Mainstone) and for the tied PhD student to work with our project partner Wessex Water pls (Ms Fiona Bowles). The three placements will enable the researchers to engage with local stakeholders and will facilitate two-way knowledge exchange between academics and practitioners.

-The science will be disseminated through high impact publications in scientific journals, including those with open access, and articles in popular publications like NERC Planet Earth, IEEM newsletters, through our project website hosted by UoB and through presentation of the findings at national and international conferences and smaller meetings attended by the above beneficiaries.