Dispersal and biodiversity impacts on community assembly and ecosystem services in shallow lake landscapes

Summary

The Rio Summit of 1992 propelled biodiversity into a global spotlight pointing to tremendous human-induced species losses in the Earth's ecosystems. Now there is an urgent need to advance our knowledge on how and why species disappear from ecosystems and the implications of these losses for important goods and services that we rely on (e.g. drinking water, food, spiritual values). One crucial landscape feature thought to have a major influence on biodiversity is connectivity - how connected habitats within the landscape are with one another. A key issue here is alteration of our natural landscapes via the creation of roads, towns and farmland. Under such circumstances natural habitats become isolated and degraded which impedes the dispersal of native species. We believe, based on preliminary evidence, that ease of dispersal across the landscape is a key feature that reduces rates of species loss in human-affected ecosystems thus preserving high biodiversity and valuable (monetary and cultural values) ecosystem services.

Lakes are uniquely useful for examining questions about biodiversity, connectivity and ecosystem services as they permit long-term (over centuries) changes in biodiversity to be studied through the analysis of fossil remains in sediment cores. The majority of aquatic organisms (e.g. algae, plants, invertebrates) leave identifiable parts in sediments, which can be dated to reveal a history of ecological change. In the proposed study we will focus on two UK lake districts: the Norfolk Broads, England and the Upper Lough Erne (ULE) lakes, Northern Ireland. Both contain numerous (60+) shallow lakes, have a long history of agricultural pollution (50-100 years) and have been subject to invasions of non-native species (notably zebra mussels). However, the Broads are mostly highly degraded, having generally turbid water with few plants, while the ULE lakes have generally clear waters and abundant and species-rich plant beds. We propose that this key difference relates to elevated connectivity amongst the ULE lakes due to a higher density of linking channels and the occurrence of winter floods which cover much of the system. This, we believe, enhances the exchange of plants and plant seeds, which in turn buffers against permanent plant extinctions in individual lakes, despite pressures from pollution.

Through the collation and collection of data on present-day water plant abundance and diversity in many individual lakes in these two systems, analysis of the amounts of carbon, nitrogen and phosphorus taken up by plants in these lakes, and by analysing sediment cores to detect changes in aquatic plant diversity and pollution over time, our research will address the following key questions:

1. Does higher connectivity buffer biodiversity loss in the face of pollution and species invasions?
2. How do changes in water plant diversity affect key functions of lake ecosystems that in turn influence the services they provide to humans?
3. Can knowledge gained from questions 1 and 2 be translated into changed conservation practices to reduce biodiversity and ecosystem service losses from aquatic landscapes?

Our project will give policy makers and conservation organisations vital information to inform landscape planning, such as the need to prioritise protection of existing high biodiversity areas (e.g. species-rich lakes) and to maintain connectivity of such sites with others. We anticipate generating an evidence-base that will argue for the maintenance or enhancement of connectivity to increase the resilience of our ecosystems to future biodiversity loss. In a world threatened by climate change, habitat fragmentation and pollution, knowledge of the relationships between dispersal, biodiversity and key ecosystem services is essential to our well being.

Who will benefit from this research?

Our project will show how considerations of dispersal and connectivity might help to better protect biodiversity and key ecosystem services in disturbed aquatic landscapes. It will be of interest to the following beneficiaries:

Policy-makers:
The proposed project should be of considerable interest to policy makers as it addresses a number of issues that are picked up by recent strategic reports (see below).

Environment agencies, conservation managers and NGOs:
The study areas are key wetland conservation sites recognised by local (county BAP targets, Local Nature Reserves), UK (e.g. SSSI, NNR), European (EU Water Framework Directive (WFD) and Habitats Directive) and International (Ramsar) conservation legislation. Consequently they are the concern of several conservation organisations, NGOs and wildlife charities, notably, IUCN, Environment Agency, NI Environment Agency (NIEA), Natural England, Broads Authority, Wildlife Trusts, National Trust, RSPB, Plantlife, Buglife, Broads Society etc. The key relevant statutory bodies have all given written support for this study.

Stakeholders and local people:
The Upper Lough Erne (ULE) and the Norfolk & Suffolk Broads lake areas are cherished by many people who use them for angling (e.g. represented by the Ulster Angling Federation [UAF - see letter of support] and the Broads Angling Strategy Group), boating, sailing and natural history (e.g. Broads Society). In addition many people live and work in these iconic wetlands and love them for purely spiritual, life-affirming and cultural reasons.

How will they benefit from this research?

Policy making and environmental planning:
Our hypothesis is that high connectivity and the existence of species-rich "core" lakes highly connected to others buffers against ecosystem degradation (e.g. eutrophication forcing, species invasions, climate change) at the regional scale, at least in the intermediate term. By extension such features may also accelerate the rehabilitation of degraded lakes. If our hypothesis holds true, policy makers and legislators will have an evidence-base from which to make key landscape-scale policy and planning decisions. Further, organisations charged with delivering EU Water Framework Directive (WFD) and Habitats Directive objectives (e.g. EA, Natural England, NIEA) will have vital information to inform decisions on conservation planning and spending. For example, it might be advisable to prioritise protection of existing high quality lakes with the knowledge that this is essential to the achievement of improvements across the rest of the system. Finally, in affording information on plant productivity and nutrient and carbon storage in plant stands within our lakes and lake districts, and how these factors vary over time, we can provide the basis for a financial analysis of some of the benefits/costs of biodiversity loss in terms of implications for receiving water courses and the value of carbon sequestered, as well as providing a larger scale perspective on the place of shallow lakes in carbon accounting.

Enrichment of people's lives:
The ULE and Broads wetlands are beautiful, semi-natural areas of the UK. By giving a clear direction to local conservation management our project will help to maintain and restore complex, vibrant and species-rich lake networks e.g. multiple clear water lakes with abundant and diverse population of plants. In this respect both residents and visitors to the two lake districts will benefit from the services (e.g. clean water, fisheries, natural history) that the wetlands provide. Local populations are passionate about the Broads and ULE lakes due to long-standing connections with the landscape and if our project helps to protect their ecological integrity into the future, then generations of local people will benefit.