Dispersal is key to biodiveristy
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. 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.
Study sites and methods
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. 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. This history of change is going to be compared to spatial patterns in biodiversity as observed today during field surveys of biodiverity.
One hypothesis to be tested
Both the Broads and ULE 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 large-scale winter floods. This, we believe, enhances the exchange of plants and plant seeds, which in turn buffers against permanent plant extinctions in individual ULE lakes, despite pressures from pollution and invasive species.
In our study we will seek to test these ideas through studies of present-day macrophyte abundance and diversity in lakes from the Broads and ULE, 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 nutrient-enrichment over time. Importantly we will consider the implications of our findings for ecosystem service provision and conservation practices in these are other similar lake networks in the UK and Europe. 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 human well being.