Tessa Driessen*1, Dave Ryves 1, Keely Mills 2
1 University of Loughborough
2 British Geological Survey
Tropical freshwater lakes are critical natural systems of global importance. In western Uganda, crater lakes and their catchments provide vital ecosystem services (e.g. drink water, aquaculture and ecotourism) to some of Earth’s fastest growing and most vulnerable human populations. However, these key services are under increasing threat due to climate change and the impact of human activities. Anthropogenic impacts include rapid change in many crater lake catchments as a result of clearance and land use alteration, while climatic impacts consist of an increase of temperature and has also led to alterations in crater lake ecosystems. Both climatic and anthropogenic impacts on these fragile ecosystems, such as ecological and biogeochemical functioning, are largely unknown.
Previous palaeoecological research carried out in this region had a main focus on either the big lakes, such as Lake Victoria and Lake Tanganyika, or long term changes in the climate. Little attention has been given to the more recent changes in ecosystem functions driven by climate or humans, or on smaller regional ecosystems. To fill in these gaps this project targets a number of crater lakes in western Uganda with contrasting catchments. To test the hypothesis of my PhD that agricultural intensification in these lake catchments has led to a significant increase in aquatic primary production, with climate change a subordinate factor. Sediment cores (spanning the last c. 50-200 years) are being analysed for fossilized pollen and diatoms on a high resolution to study the impact of human activity and recent surface water warming on biogeochemical cycling and its associated impacts on the ecological functioning of these lake systems.
Preliminary diatom results demonstrate that these crater lakes are sensitive to changes in the recent past. Many lakes and their catchments have been heavily impacted by humans over the past 50 – 200 years, and their sediment records reveal major ecological changes compared to lakes in more “pristine” catchments . Understanding past anthropogenic and climatic influences on these ecosystems can act as a guide to their future resilience and sustainability as natural resources providing vital ecosystem services for local populations under increasing environmental change.