Wind energy and UK peatlands
Energy returns require turbines to be sited in areas of high wind which, in the UK, frequently correspond with the occurrence of peatland. UK peatlands occupy only 10% of the land surface and yet represent our largest terrestrial carbon store which has accumulated over hundreds of years (Ostle et al., 2009). Globally peatlands contain twice as much carbon as the atmosphere (Roulet, 2000; Schlesinger & Andrews, 2000) and are home to uniquely-adapted plants and animals. These living ecosystems and their carbon reservoirs are known to be vulnerable to changes in land use and climate (Freeman et al., 2004; Armstrong et al., 2010).
Wind turbine effects on peatland carbon
Installation of wind turbines on peatlands and management of the peatland can strongly influence overall ecosystem carbon budgets (Nayak et al., 2008). Wind turbines remove wind by conversion to mechanical energy, which produces electricity. Consequently there is a ‘wake-effect’ downwind of each turbine (Crespo et al., 1999), which can persist for at least 15 times the turbine diameter (Chamarro & Porte-Agel, 2009). The effect of this wake on the microclimate and carbon cycling represents an important ‘gap’ in our understanding of how wind farms affect UK peatland carbon stocks and associated green house gas (CO2, CH4 and N2O) emissions.
Reduced wind speed and increased turbulence in the turbine wake may produce downwind microclimates. However, detailed effects on parameters such as temperature and evapotranspiration, have not been fully examined. One recent wind farm study has shown that downwind of a wind farm temperatures are lowered through the day and raised at night (Baidya Roy and Traiteur, 2010). These microclimatic differences may affect hydrological and plant-soil carbon cycles.
Other research has shown that changes in local climate (temperature and moisture) can have important impacts on peatland carbon cycling (Briones et al., 2004; Clark et al., 2005) with implications for peatland carbon sequestration and storage. Consequently, altered microclimates induced by wind turbines may affect carbon cycling in peatlands.
Carbon dioxide production increases with temperature – Briones et al. (2004)
Increases in DOC are related to increases in temperature – Clark et al. (2005)
Wind turbine effects on plant-soil biodiversity
Peatlands are important living reservoirs of uniquely adapted plants and animals (Parish et al., 2008). Peatland biodiversity is potentially vulnerable to changes in land use, management and climate. Understanding of plant-soil biological responses to land use and climate change in peatlands remains poor. This knowledge gap makes it difficult to develop positive guidance for the management of peatland biodiversity.
Wind turbine induced microclimates may modify biodiversity, through effects on the temperature, and water table depth. Temperature has been shown to play a part in governing the rates of chemical reactions and the growth and activities of biota in and above the peat (Artz, 2009). The position of the mean water table controls both the plants that can grow above ground and the ratio of aerobic to anaerobic microbial processes below ground that produce and consume CO2 and CH4 (Bardgett, 2005).
There are two components of WP1:
Field component: At Black Law wind farm, Scotland, we will examine peatland ecosystem responses to turbine-induced microclimate. From three typical vegetation assemblages, replicated at four sites located across the projected wind farm microclimate gradient, we will monitor green house gas (GHG) fluxes (CO2, CH4 and N2O), and pore water dissolved organic carbon concentration and character. Environmental variables including water table depth, soil moisture, soil temperature and surface temperature, will also be monitored. This will reveal if the peatland responds to a projected microclimatic gradient, and allow us to model annual fluxes using data from co-located automated weather stations.
Laboratory component: The interactive effects of microclimate changes on peat microbial communities and their activity will be investigated through a range of factorial (water table, temperature, vegetation assemblage) experiments with peat cores taken across the microclimatic gradient. Peat will be incubated in controlled environment rooms (5-20oC), and measurements made to quantify GHG emission and characterise the microbial community from biomarker analyses. Through temperature manipulations we will test for interactions between turbine microclimate and vegetation and their effects on GHG fluxes and microbial community structure.
This project is the first to address the impact of wind energy on carbon sequestration in peatland environments and consequently provide information on the resilience and adaptation of peatlands to hosting renewable energy. This ‘gap’-filling knowledge will contribute to the development of management strategies and policy to maximise the carbon and biodiversity benefits of renewable wind farm energy provision from peatlands.