Nitrogen Deposition Implications of the Local Plan Durham County Council: Ecology Team February 2012 1. Background Nitrogen emissions to the atmosphere have increased substantially over the 20th century, mainly in the form of ammonia (NH3) from agriculture and nitrogen oxides (NOx) from industry. The main pollutants of concern for European sites are oxides of nitrogen, ammonia and sulphur dioxide (SO2). Following atmospheric dispersion and chemical transformation, these chemicals are deposited across European landscapes. A large number of the habitats (and species, either directly or indirectly) listed under the Habitats Directive are sensitive and potentially vulnerable to atmospheric nitrogen deposition. Nitrogen is the second most important plant nutrient behind carbon, and the productivity of terrestrial ecosystems is generally limited by nitrogen supply. However such communities exist in balance because their growth rates are contained by the level of available Nitrogen. Hence the increase in nitrogen deposition will be expected to exert a large impact on ecosystem biodiversity. Nitrogen deposition may cause changes to species composition, often including a reduction in species richness and a loss of sensitive ‘lower plants’; changes to soil microbial processes; changes to plant and soil biochemistry; increased susceptibility to abiotic stresses (such as winter injury) and biotic stresses (such as pests and pathogens); and it also contributes towards acidification. Ammonia emissions are dominated by agriculture, with some chemical processes also making notable contributions. Nitrogen emissions are much more widely dispersed than ammonia, with the latter often deposited in high quantities to semi-natural vegetation in intensive agricultural areas. Reduced Ammonia is primarily emitted from intensive animal units and more recently vehicles with the introduction of catalytic converters. Thus effects of Ammonia are most common close to urban highway and roadside verges, and roughly within 500m of the point source depending on the size of the source. Aerosols of Ammonia, by comparison, are carried much further and contribute to wet deposition1. As such, it is unlikely that material increases in Ammonia emissions will be associated with Local Plans. The loading of Nitrogen in wet deposition will depend on the amount of precipitation and the amount of Nitrogen. In the east, Nitrogen concentrations can be quite high due to the low rainfall, whereas in the west where the rainfall is much higher, the concentrations tend to be lower (www.apis.ac.uk). Nitrogen emissions, however, are dominated by the output of vehicle exhausts (more than half of all emissions). The EU has been tightening emission standards on new vehicles through various phased Euro standards. However, the “lab based” theoretical improvements have not translated into the real world situation in the UK. Higher vehicle numbers on the UK roads and the level of congestion means that the cars are performing worse in terms of national emissions than had been calculated2. Within a ‘typical’ housing development, by far the largest contribution to Nitrogen (92%) will be made by the associated road traffic. Other sources, although relevant, are of minor importance (8%) in comparison. Emissions of Nitrogen could therefore be reasonably expected to increase as a result of greater vehicle use as an indirect effect of the Local Plan. 1 Wet deposition refers to acidic rain, fog, and snow. If the acid chemicals in the air are blown into areas where the weather is wet, the acids can fall to the ground in the form of rain, snow, fog, or mist. As this acidic water flows over and through the ground, it affects a variety of plants and animals 2 Challenges to reducing the threat of nitrogen deposition to the Natura 2000 network across the UK and Europe (Bareham) 2011. 2. The Habitats Directive The Habitats Directive requires that all ‘plans and projects’ which are likely to have a significant effect on a Natura 2000 site have an appropriate assessment of the implications for the site. Subject to certain exemptions, the plans or projects can only be approved where they are shown to have no adverse effect on any Natura 2000 site. However, at present, there is no common approach for evaluating the effects of nitrogen deposition and concentrations on these sites. For the conservation status of a habitat to be favourable, “the specific structure and functions which are necessary for its long-term maintenance exist and are likely to continue to exist for the foreseeable future”. Habitat structure and habitat function varies widely between different habitats, but it is clear that the various ecological processes essential for a habitat have to be present and functioning for the habitat to be considered to be at favourable conservation status (European Commission, 2006). 3. Critical Loads The relationship between pollutant dose and the resulting environmental effect forms the basis for the critical load concept. The critical load is defined as: ‘A quantitative estimate of an exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge.’ (http://www.unece.org/env/lrtap/WorkingGroups/wge/definitions.htm) Critical loads of Nitrogen can be compared to past, present or future deposition rates in order to establish the amount of excess deposition, also called exceedance. In the UK the Air Pollution Information System (APIS) provides a comprehensive source of information on pollution and its impact on habitats and species. APIS has been developed by JNCC (Joint Nature Conservation Committee), the country conservation agencies, the UK environment agencies and the Centre for Ecology and Hydrology. It provides site specific information on deposition and critical loads. 4. The Current Situation in County Durham Despite not necessarily being listed under each sites vulnerabilities, in County Durham all of the designated N2K sites within the county boundary currently exceed the critical load for Nitrogen, with acid deposition also a problem at Castle Eden Dene, Moor House-Upper Teesdale, and the North Pennine Moors. Therefore as agreed by Natural England - any new source of pollution deposition is likely to exacerbate an existing adverse threat to these vulnerable sites. As detailed above, the majority of the likely source of Nitrogen is likely to come from an increase in traffic on the County main roads, due to increased housing and office/industrial development. While it is recognised that the Local Plan also needs to tackle the issue of general diffuse air pollution (airports, power stations etc) this cannot be addressed at the local level. Durham County Council is only responsible for avoiding the individual contribution of the Local Plan to the “in combination” effect not for mitigating the “in combination” effect in its totality. 5. Intensive Livestock Industry Under the provisions of the IPPC Directive, large pig and poultry units are currently being authorised in the UK. Where these units are sited near to Natura 2000 sites and are judged to have a significant effect, they require an ‘appropriate assessment’ under the provisions of the Habitats Directive. A number of studies from the early 1990’s have demonstrated that ammonia emissions from these units can be many times the critical level and critical load for the receiving habitat (Sutton et al, 2009). There are currently however no application for any new large scale cattle units/pig farms/poultry farms in the county. The likely impacts caused by increased ammonia deposition have therefore not been considered further. 6. Is There Evidence to Suggest that Nitrogen Deposition is Impacting on the County’s Natura 2000 sites? Site condition assessments: The condition of SSSI (Site of Special Scientific Interest) land in England is assessed by Natural England, using categories agreed across England, Scotland, Wales, and Northern Ireland. The conservation agencies’ monitoring of SSSI condition is based on Common Standard Monitoring (CSM) guidance http://www.jncc.gov.uk/page-2219 . CSM provides a basic framework to ensure consistent monitoring in the UK. The main purpose of site assessment is to: • determine whether the desired condition of the feature(s) of interest for which the site was designated is being achieved. This can enable judgements to be made about whether the management of the site is appropriate, or whether changes are necessary; and • to enable managers and policy makers to determine whether the site series as a whole is achieving the required condition, and the degree to which current legal, administrative and incentive measures are proving effective. There are six reportable condition categories: • favourable; • unfavourable recovering; • unfavourable no change; • unfavourable declining; • part destroyed; and • destroyed. These site condition assessments currently provide the only regular means of assessing the state of the component SSSI’s within our European Sites. Utilising this as a means of assessing the current state of the County’s European Sites, the following is evident: • Moor House Upper Teesdale SAC – Majority unfavourable recovering • North Pennine Dales Meadows SAC – Majority favourable • North Pennine Moors SAC/SPA – Majority favourable • Castle Eden Dene – Majority unfavourable recovering • Teesmouth and Cleveland Coast SPA – Majority unfavourable recovering • Northumbria Coast SPA – Majority favourable •