A guest post from Dr Valerie McCarthy, Assistant Lecturer at Dundalk Institute of Technology, Ireland.
Groundwater Dependent Ecosystems (GDEs) are geologically and physio-graphically complex and are recognised as an important but, nevertheless, poorly understood set of habitats. At a recent event organised by the Hydrogeological Group of The Geological Society, held at the at the Birmingham and Midland Institute, the audience were presented with an excellent overview of current research activities into GDEs covering a variety of topics relating to effective monitoring, conceptual understanding and management of this valuable range of habitats, while providing an opportunity to address issues surrounding current and future research and policy challenges.
What is a GDE?
A GDE is one in which the plant and animal community is dependent on the availability of groundwater to maintain its structure and function. Groundwater is, therefore, integral to sustaining the ecological health of these systems and any activity which alters the quantity or quality of groundwater can have negative impacts on the flora and fauna. This immediately brings its own set of challenges, for in order to fully understand these systems it is necessary to bring together a range of expertise and knowledge from a diverse variety of scientific disciplines including hydrology, geology and ecology. A task no less challenging that it will be effective, which was recognised at several stages throughout the day. Case studies were presented which showed where this approach was effective. Only by synthesising data and methods from different fields of science will new insights into the functioning of these ecosystems be obtained.
Why are they important and how can they be protected?
Groundwater dependent ecosystems are fragile and prone to damage through drainage for agriculture, over exploitation of groundwater resources for drinking water, pollution from industrial, domestic and agricultural activity and peat extraction. Yet these ecosystems are important, not only for the services they provide in terms of conservation and biodiversity, but also their economic importance with recreational, aesthetic and cultural value. Furthermore, they can have a role to play in the retention of nutrients from the surrounding catchment, they may act in flood defence and can be important stores of carbon.
Many groundwater dependent ecosystems have been damaged and no longer provide full ecological and hydrological functions or ecosystem services. Loss of these habitats has prompted the European Union to introduce legislation requiring member states to protect GDEs. The Habitats Directive requires long term conservation of protected sites, but additionally the implementation of restoration measures to return restorable areas to favourable conservation status. In addition, the Water Framework Directive (WFD) supports the integrated management of water resources and requires that GDEs be protected from significant damage. The day started with presentations covering the challenges policy makers and water managers face in successfully implementing requirements of the Habitats Directive and WFD, both of which necessitates a conceptual understanding of the ecohydrogeology of GDEs.
What are the different types of GDE?
Groundwater dependent ecosystems cover a range of habitat types (e.g. dune slacks, raised bogs, transition mires, calcareous fens etc.). Some of these habitats are unique or rare outside of certain geographic regions. The turlough is one such example. It is an ephemeral karst lake which results from high rainfall and consequently high groundwater levels. Therefore, these fascinating systems can dramatically go from being relatively dry pasture ground to full lakes during the wetter months of the year, and owing to their characteristic ecology have been designated as a Priority Habitats by the EU Habitats Directive. Only through detailed investigations will it be possible to gain the baseline information necessary to improve the conservation management of this distinctive and irreplaceable habitat.
Groundwater dependent ecosystems also provide habitat for a unique range of biota. These organisms not only include terrestrial and aquatic plants and animals, but also a group of organism which are found only in the groundwater itself and are known as stygobites. In one of the final talks of the day an overview was given of these unique fauna. Most are small crustaceans, worms and microbes adapted to live underground where they are highly adapted to an environment lacking light and with limited resources. There are only eight species of stygobitic macro-invertebrate species recorded in England and Wales, however, very little is known about their spatial distributions and ecology. The presentation served as a reminder of the importance of this often overlooked groundwater dependent ecosystem and the vulnerability of its biological community to environmental change.
Groundwater dependent ecosystems are important natural environments. However, effective protection and management of these ecosystems may be hindered by inadequate information particularly in relation to the environmental supporting conditions required to maintain GDEs in a favourable state. More work is, therefore, required in order to fully define the environmental requirements of these ecosystems. Increased knowledge will allow for improved management and protection of this important natural resource.