UK Research on The Eutrophication and Acidification of Terrestrial Ecosystems

Background:

Energy production through the combustion of fossil fuels results in the emission of nitrogen oxides and sulphur dioxides into the atmosphere. Food production results in ammonia emissions from farm animal units, and nitrogen oxides emissions are linked to intensive fertiliser use. These pollutants are transported in the atmosphere, affecting the quality of the air and rain across the UK. Pollutant deposition has led to nitrogen enrichment of semi-natural upland habitats (i.e. eutrophication) and acidification of soils and waters in acid-sensitive areas leading to loss of, or undesirable change, in biodiversity. Reductions in emissions due to policy control measures have achieved a reduction in the quantity of sulphur and nitrogen oxides falling on different habitats but, unfortunately, due to increases in emissions from shipping, recovery has not been as fast as hoped for. Ammonia emissions increased sharply from 1950s to 2000 but currently remain at these peak levels.

A major driver for pollutant control measures is the aim to reduce damage to sensitive ecosystems. The potential for damage is calculated as the area of land which receives more than the critical load of a specific pollutant or pollutant type. The critical load is defined as the amount of pollutant deposited on an ecosystem that, if exceeded, could lead to damage of that ecosystem. The critical loads are improved and refined as new data on ecosystem impacts become available. The new challenge for the scientists is to inform policymakers on when and where the ecosystem effects will occur - both the damage and the recovery from acidification and eutrophication - and how factors such as land management and climate change may enhance or moderate these impacts. This will help inform revisions of both the EU National Emissions Ceiling Directive and the UNECE Convention on Long Range Transboundary Air Pollution (CLRTAP) Gothenburg Protocol in 2008 and future revisions of the UK Air Quality Strategy. In addition it will provide the tools and data to understand trends observed in response to the implementation of current and future emissions reduction policies. This is the challenge for the Terrestrial Umbrella: Effects of Acidification and Eutrophication on Terrestrial Ecosystems and their recovery.

The terrestrial umbrella consortium is a group of researchers and organisations which will carry out of suite of integrated projects.The main aims are to:
(i) collate data which provide evidence for damage or recovery in a range of terrestrial habitats due to nitrogen deposition, (ii) determine whether factors such as the form of nitrogen, grazing pressure or traits of plants present modify the impacts observed; (iii) test proposed indicators of change in both experimental and survey settings, (iv) clarify what determines the fate of nitrogen in soil which acts as the main sink for nitrogen; (v) contribute to the development of linked ecosystem model chains to forecast likely timing of responses in both soils, vegetation composition and their interdependence; (vi) collate survey data and continue long term manipulation experiments to help test and develop model chains; (vii) examine the potential modifying and interactive effects of climate change with the effects of nitrogen deposition; (viii) support the UK National Focal Centre for Critical Loads Mapping, provide knowledge transfer to range of stakeholders and disseminate information through an annual air pollution conference (CAPER).

Approaches used will include continuation of a unique series of long term field manipulation experiments which involve experimental nitrogen applications in the different forms it is deposited to ecosystems (wet and dry, NOx and NHy) and in combination with other drivers of change i.e. grazing, burning, warming and drought in a range of habitats from heathlands to grasslands and wetlands. We will also undertake new large-scale surveys across deposition gradients and revisit past survey sites to identify changes in vegetation and soil over the last few decades and relate these to drivers of change including nitrogen deposition. Detailed soil process studies will utilise isotopic techniques to identify controls on nitrogen retention and release. Model development will focus on defining what is the habitat requirements for UK higher plants and how these may change in response to different pollution scenarios thus enabling us to predict possible future changes in biodiversity. We will also develop methods which will allow us to predict which plant species may invade habitats and how climate change may affect these responses due to changes in carbon cycling.

The Terrestrial Umbrella is part of a consortium of three projects funded by Defra with linked but separate objectives: (i) the Terrestrial Umbrella (TU) presented here, (ii) the Freshwater Umbrella  and (iii) the Critical Loads and Dynamic Modelling Umbrella

 

Page last modified: 09/11/2010
Page published: 27/08/2010