Air Pollution Symposium
Proceedings from the JNCC Air Pollution and
Ecosystem Change Symposium
A symposium held on 28-29 October 2003, in Caernarfon, North
Wales.
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Workshop objectives and
background
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Introduction |
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Setting the Scene
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Air pollution and ecosystems in the United
Kingdom
Professor David Fowler, Centre for Ecology and Hydrology
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Presentation
(PDF, 2.27MB) |
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Evidence of change - findings of CS2000 and New Plant
Atlas
Dr. Trevor Dines, Plantlife
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Presentation
(PDF, 314KB) |
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Air pollution policy and implications
Dr. Alison Vipond, Department of Environment, Food and Rural
Affairs
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Abstract |
Presentation
(PDF, 612KB) |
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Research update
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Nitrogen effects and fate in ecosystems
Dr. Bridget Emmett, Centre for Ecology and Hydrology
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Presentation
(PDF, 115KB) |
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Woodland monitoring in the UK
Dr. Mark Broadmeadow, Forest Research
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Abstract |
Presentation
(PDF, 981KB) |
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Development and application of empirical critical loads
for nitrogen
Professor Mike Ashmore, Bradford University
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Abstract |
Presentation
(PDF, 354KB) |
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Air pollution monitoring in the UK
Dr. Brian Reynolds, Centre for Ecology and Hydrology
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Abstract |
Presentation
(PDF, 1.77MB) |
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Air Pollution Assessment
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Determining impacts and risk – information requirements
of the pollution regulators
Dr. Jon Foot, Scottish Environment Protection Agency and
Mr. Jim Storey, Environment Agency
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Abstract |
Presentation
(PDF, 1MB) |
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Bio-indicator methods for monitoring of nitrogen
impacts on statutory nature conservation sites
Dr Mark Sutton, Centre for Ecology and Hydrology
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Abstract |
Presentation
(PDF, 288KB) |
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Atmospheric nitrogen pollution impacts on
biodiversity
Dr. Jane Goodwin, Department for Environment, Food and Rural
Affairs
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Abstract |
Presentation
(PDF, 234KB) |
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Site assessment and common standards
monitoring
Mr. Wyn Jones, Joint Nature Conservation Committee
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Presentation
(PDF, 2.47MB) |
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| Workshop – Understanding the impacts of air pollution
on the SSSI series |
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The workshop session required groups to consider the options
for assessing the impacts of air pollution on the SSSI
series.
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Background and
Objectives
The conservation agencies were involved in the membership of
Defra's recent National Expert Group on Transboundary Air Pollution
(NEGTAP). The NEGTAP report provides an assessment of air pollution
effects from acidification, eutrophication and ground level ozone.
Forecasts of the situation in 2010 are also made, a date when all
existing air pollution legislation and scheduled emission
reductions will be in place.
The report concludes that many of our most valuable habitats
will still be suffering the adverse impacts of excess pollution
from sulphur and nitrogen compounds, in combination with increasing
background levels of ground level ozone. For example, in 2010
critical loads for acidification will be exceeded in nearly half of
UK ecosystems, while critical loads for eutrophication will be
exceeded in 40% of UK 1km x 1km grid squares with heathland and 20%
with sensitive grassland. This is clearly at variance with the UK
Government's domestic and international responsibilities to protect
these sites from harm.
The conservation agencies, as advisers to the Government and
its devolved administrations, have a vital role to play in advising
on pollution reductions necessary to protect the natural
environment. In order to fulfil this responsibility the
conservation agencies will need to better understand the impacts of
air pollution on national and international wildlife sites, and the
wider countryside.
One of NEGTAP's key recommendations was to provide
site-specific links between the pollution field and what we observe
on the ground. This presents the conservation agencies with a major
challenge and we must make every effort to articulate the condition
of our designated sites in the context of air pollution. This
information will be required to inform JNCC's advocacy for further
and more targeted cuts in emissions of air pollutants. It is also
required in order to better inform our staff with regards the
threats of air pollution and how this might interrelate with the
conservation objectives, monitoring and management of sites, and to
inform our advice on air pollution related casework.
The Air Pollution and Ecosystem Change Symposium is being run
jointly by the Air Pollution and Uplands Lead Co-ordination
Networks. It will bring together habitat specialists from the
conservation agencies, external air pollution experts and policy
and practitioners from Government and Government agencies.
The objectives of the symposium are:-
- To raise awareness amongst conservation agency staff of
air pollution issues and their relevance to nature conservation and
site protection.
- To consider how we can better understand the impact of
air pollution on the condition of statutory sites and what role the
conservation agencies play.
The need for the symposium is drawn out of the recommendations
of NEGTAP and also the need to address these issues in order to
influence subsequent rounds of domestic and international air
pollution policy. NEGTAP identified nitrogen compounds as one of
the greatest threats to the integrity of ecosystems. This fact
together with the wider countryside enrichment observed in CS2000
and the New Plant Atlas for British and Irish Flora suggest that
the main emphasis of the symposium should be on nitrogen pollution,
though acidification and ozone will be covered briefly.
Air Pollution Policy and
Implications
Dr. Alison Vipond
Air and Environment Quality Division
Department for Environment, Food and Rural Affairs
The sources of air pollution are many and varied, ranging from
industrial, agricultural and road transport to domestic and natural
sources. It is recognised that air pollution can adversely affect
health, materials and vegetation. Air pollutants can travel through
the atmosphere over long distances, their effects being experienced
over a range of scales – local, national, continental and even
hemispheric, for some pollutants. Good progress in controlling many
emissions is being made. For example, UK emissions of sulphur
dioxide have been cut by 80% since their peak in the 1970s, and
emissions of nitrogen oxides have nearly halved since the early
1990s, bringing significant improvements in air quality.
Reducing the adverse effects on vegetation from acid and
nitrogen deposition and from ground-level ozone, continues to be a
major driver of international agreements on emission reductions.
The EC National Emissions Ceilings Directive (NECD) and the UNECE
Gothenburg Protocol are the two most recent agreements to curb
emissions, aiming to reduce acidification, eutrophication and
ground-level ozone. An effects-based approach to identify possible
emission reduction scenarios and their costs and environmental
benefits was used to inform the negotiations. The agreements set
emission ceilings (upper limits) for sulphur dioxide, nitrogen
oxides, ammonia and volatile organic compounds, to be achieved from
2010 onwards. Notably, they are the first agreements to contain an
emission target for ammonia, a pollutant mainly derived from
livestock where little emission control has been required to
date.
Preparations are underway for the international review of the
NECD and Gothenburg Protocol in 2004/5. This will involve the
assessment of what current policies are expected to deliver and
what more needs to be done to minimise adverse effects of air
pollution on human health and the environment. The increased
understanding of the role of global air pollution, particularly
contributing to increasing levels of ground-level ozone, will also
have a bearing on international air pollution policy.
On the national scale, the Government's air quality policies
are set out in detail in the Air Quality Strategy for England,
Scotland, Wales and Northern Ireland (AQS). The Strategy describes
plans to improve and protect air quality in the UK in the
medium-term, addressing the main air pollutants. The Strategy's
objectives focus on achieving concentrations to avoid damage to
human health. There are also two objectives aimed at achieving
levels of nitrogen oxides and sulphur dioxide to avoid damage to
vegetation. The current AQS objectives for ecosystems are met, but
the problems are not solved. Defra is examining the potential to
strengthen the objectives to ensure protection of Sites of Special
Scientific Interest, compatible with the Habitats Directive and its
own Public Service Agreement.
The conservation agencies have a significant role in
developing our understanding of the impact of air pollution on
conservation sites, and in guiding the future development of policy
on emissions. In particular, an assessment of the current status of
conservation areas, with respect to damage or risks from air
pollution, is urgently required. This will raise the profile and
understanding of a potentially serious issue, and also help to
identify targets for ecosystem protection to guide air quality
policies. In addition, site management can be crucial to prevent or
slow damage or to speed up recovery, particularly where sites have
been polluted by years of historic deposition and are now showing
signs of change. Protecting our valuable habitats from air
pollution requires a combination of both management at the local
level, and action to reduce emissions at a range of scales, from
local to global. There is a growing need to fortify links between
the conservations agencies and Defra in this area.
Woodland monitoring in the
UK
Mark Broadmeadow
Environmental Research Branch,
Forest Research, Alice Holt Lodge, Farnham, Surrey,
GU10 4LH
A number of monitoring schemes are operated by Forest Research
which provide information on the state or condition of woodland
ecosystems at a national level. The Condition Survey of
Non-woodland Trees and the National Inventory of Woodland and Trees
were not designed to provide information on air quality, but both
include an assessment of a number of indicators of the general
state of trees or woodland. Furthermore, the range of attributes
assessed in the latter scheme, together with its scale (40 000
ground truthing plots) provides a potentially valuable resource for
air pollution studies. In contrast to these two general woodland
condition monitoring schemes, the Environmental Change Network, the
Forest Condition Survey (formerly the Forest Health Survey: Level
I) and the Intensive Forest Health Monitoring Network (Level II)
were all established to monitor the effects of air pollution, and
in the case of the last of them, to identify cause-effect
relationships.
The Forest Condition Survey is an annual assessment of crown
transparency and growth, together with a number of other measures
of state, on more than 300 plots covering five species – oak,
beech, Scots pine, Norway spruce and Sitka spruce. Inter-annual
variation is evident, particularly in Sitka spruce and beech as a
result of insect defoliation and seed production, respectively. No
long-term trends are apparent with the possible exception of a
limited deterioration in oak, which may be an artefact of initial
survey design. Spatial variation in condition has been
investigated, and relationships are evident between both needle
retention and insect damage in Scots pine and mapped nitrogen
deposition. An extension study also revealed a weak relationship
between the nitrogen status of the ground vegetation and distance
to the woodland edge in a sample of the beech plots.
Wider comparisons and analyses within Europe also are possible
through involvement with the European Large-scale Forest Condition
Survey, in which over 6000 plots are assessed. The Intensive Forest
Health Monitoring Programme is a second pan-European Programme,
involving over 500 sites across Europe of which twenty are located
in the UK. More detailed information is provided on the physical
environment, enabling trends and cause effect relationships to be
elucidated. A comparison of two Scots pine plots demonstrates
contrasting responses. Recovery from past acid deposition is
evident at a site in the English Midlands, while soil acidification
and the effects of excess nitrogen deposition are now becoming
apparent at a plot in Thetford forest, an area of intensive animal
husbandry where deposition is dominated by reduced nitrogen.
Concern is now focussing on the current and future effects of
tropospheric ozone pollution which presents difficulties in its
analysis and interpretation for forest ecosystems. Routine
monitoring has indicated limited damage to trees in the UK, but the
use of bio-indicators in the form of shrub species may prove to be
a more suitable approach.
An overall assessment of the condition of British forest based
on the available monitoring information is that they are generally
in a favourable condition with no long-term trends apparent and
that air pollution is not currently affecting the health of trees
to a significant extent. Climatic events in individual years
together with the effects of insect pests and pathogens are more
important determinants of forest condition than the air pollution
environment, and this position is likely to continue given the
predictions of climate change. However, when the wider forest
ecosystem is assessed, some detrimental effects of enhanced
nitrogen deposition are apparent, although not to the extent that
might be expected given the scale of nutrient nitrogen critical
load exceedance.
Development and application of
empirical critical loads for nitrogen
Professor Mike Ashmore
Department of Geography and Environmental Science
University of Bradford
The critical load concept was first developed in the context
of European scale negotiations on reductions of sulphur and
nitrogen emissions that were based on reduced the environmental
impacts of these pollutants most effectively (by minimising
critical load exceedance). The critical load of nitrogen deposition
is that below which harmful effects on ecosystem structure and
function do not occur according to current knowledge; in the case
of empirical critical loads for nitrogen, these are based on a
qualitative assessment of field and experimental evidence, rather
than mass balance calculations. New critical loads for use in
European scale evaluations were agreed at a workshop held in Berne,
in November 2002.
But how useful are these critical loads for assessing the
impacts of nitrogen deposition in the U.K.? This paper will briefly
consider three important issues related to this question ,
focussing primarily on grasslands, heathlands and bogs and
mires:-
- How have the Berne workshop recommendations been used to
develop maps of critical loads and their exceedance for the
UK?
- Is the fact that significant areas of the UK receive nitrogen
deposition above the critical load for that ecosystem consistent
with the field and experimental evidence in this country?
- Can critical loads be used reliably in risk assessment for
specific sites?
I conclude that the national maps of critical loads and their
exceedance are broadly consistent with the rather limited evidence
that we have available on the ecological impacts of nitrogen
deposition in the UK, and are valuable in the context of broad
national policy development. However, a critical question for
interpretation of the field data, and for predicting the
consequences of reductions in nitrogen deposition, is the timescale
of response, which in terms of effects on community composition of
vascular plants, but not lichens and bryophytes, may be decades.
Furthermore, there are major limitations in applying the critical
load values in assessments of individual sites with their specific
deposition and management histories, and nutrient status.
Air Pollution Monitoring in the
UK
Dr. Brian Reynolds
Centre for Ecology and Hydrology
The UK monitoring networks relevant to acidification, nitrogen
deposition and ozone are reviewed. The atmospheric deposition / air
quality monitoring networks are probably adequate to define broad
spatial patterns and changes in the pollution climate of the UK.
Their usefulness for site specific assessments is limited by
factors such as the relatively coarse resolution of the mapping and
within grid cell variability. Point source emissions and the
effects of complex terrain on wet deposition contribute
significantly to the latter. The core monitoring network of
freshwater sites (the UK Acid Waters Monitoring Network) is
providing evidence of recovery from acidification and a basis for
predictive modelling. Additional sites operated by individual
research organisations provide complimentary data in acid sensitive
areas of Scotland, the Lake District and Wales. In contrast, but
with the exception of forestry, monitoring data for semi-natural
systems and soils are dispersed and disparate with no networks
specifically targeted at monitoring acidification / nitrogen
impacts. Relevant information can be gathered from networks such as
the ECN and from repeated surveys such as CS2000. However our
ability to assess the effectiveness of emissions control policies
and predict future responses for semi-natural systems is inhibited
by the lack of a co-ordinated monitoring network.
Determining
Impacts and Risks - Information Requirements of the
Pollution
Dr. Jonathan Foot, Scottish Environment Protection
Agency
Mr. Jim Storey, Environment Agency
There are nearly 800 candidate SACs and over 200 SPAs in the
UK. The Habitats Directive requires 'measures taken...shall be
designed to maintain or to restore, at a favourable conservation
status, natural habitats and species of wild fauna and flora of
community interest.' Competent Authorities must review the effects
of existing permissions, alone and in combination with other
permissions, in light of conservation objectives for SACs/SPAs.
Depending on the likely effect the permission may be having, they
must confirm, amend or revoke the permission.
There have been significant reductions of sulphur dioxide and
oxides of nitrogen emissions but a number of these internationally
protected habitats will remain in areas where the effects of air
pollution will exceed environmental standards. Also, unfortunately,
there has probably been little reduction in the releases of ammonia
to atmosphere. Around 70% of terrestrial habitats and 25% of
freshwater sites are under threat from acidification.
Eutrophication is likely to be adversely affecting 65% of ecosystem
areas.
SEPA and the Environment Agency have embarked on an assessment
of the impacts of critical load and critical level exceedance to
the habitats and species at each site. The regulators have agreed
to follow a 4 stage procedure, the first two steps of which is to
screen out industrial processes which have no relevance or no
likely significant effect on individual sites. Recently, SEPA, the
Environment Agency and the NI Environmental Heritage Service have
embarked on a major screening exercise to utilise Defra's recent
remodelling of acid and nutrient nitrogen deposition for the UK.
The deposition from major industrial sources is being added onto
this "background" data and compared to critical loads for the
features and habitats of sites.
If the process does not fail the relevance and significance
tests then an appropriate assessment of its effects must be made.
If a likely significant effect is found then the regulator must
investigate and implement options to improve the status of the
site, including requiring the process to close down.
The conservation agencies have an essential role in this work
and it is very important that they help ground truth the various
stages and ensure the assessment is carried out against the correct
features and habitats. It is also crucial that they provide
information on other aspects which may be affecting the integrity
of the sites.
Bio-indicator methods for monitoring
of nitrogen impacts on statutory nature conservation
sites
M.A. Suttona, I.D. Leitha,
C.E.R. Pitcairna, Netty van Dijka, Lucy
Shepparda,
Sim Tanga, R. Mitchellb, S.
Smartc, D. Fowlera
Centre for Ecology and Hydrology: aEdinburgh,
bBanchory and cMerlewood
Pat Wolseley, William Purvis and Peter James
Natural History Museum, London
Atmospheric nitrogen deposition represents a threat to
naturally nutrient-poor plant communities, leading to a loss of
conservation value in of importance for statutory nature
conservation sites. Until now, the regulatory assessment of these
impacts has been focused on the critical loads approach, where
estimated atmospheric deposition loads are compared with 'critical
loads' to estimate the occurrence and extent of 'critical load
exceedance'. This provides a risk assessment that indicates the
likelihood of future change. However, it does not indicate whether
changes are already occurring on a site or provide a means to
monitor the extent of actual change.
Bio-monitoring complements the critical loads approach in that
it provides information on the actual condition of the sites of
interest. The range of bio-monitoring techniques for nitrogen
includes: a) biochemical measures of nitrogen accumulation, b)
measures of species composition of different components and c)
methods involving the transplanting of live plant material. The
different techniques are variously suited to act as bio-indicators
of atmospheric deposition, air concentrations of reactive nitrogen
compounds and/or ecological change, and may be applied by spatial
comparisons at a single point in time or for bio-monitoring over
periods of several weeks to many decades. A very wide range of
potential methods is available, and these vary in robustness,
potential artefacts, characteristic response time, technical
requirements and costs. This presentation reports ongoing work
commissioned by JNCC and the UK conservation agencies to review,
test and refine the most cost-effective bio-monitoring techniques
for application at statutory nature conservation sites.
Of the biochemical methods, the tissue nitrogen concentration
of bryophytes and Calluna is without doubt the best-characterized
parameter to indicate atmospheric nitrogen deposition. While a
range of responses has been observed in the past, standardized
protocols are a key to obtaining consistent results. Although there
is uncertainty regarding the level of tissue nitrogen at which
plant community changes will occur, the method can be used (with
confidence limits) to estimate whether atmospheric deposition is
significantly above or below the critical load. A similar principle
applies to the measurement of foliar amino acids and two more
recently recognized parameters: soluble foliar ('substrate')
nitrogen and foliar ammonium. Recent data show that the smaller the
pool size, the larger the nitrogen response: over a local gradient
of ammonia deposition, the foliar concentrations of total N,
soluble N and ammonium increased by factors of 3, 5 and 20,
respectively. The latter technique, in particular, appears to be
sensitive, fast response and low-cost and is being tested
further.
Species composition methods, by definition, represent the
changes of most interest for conservation agencies. In approaches
applying the Ellenberg nitrogen scale, each higher plant and
bryophyte species is assigned a nitrogen preference score, allowing
habitat-weighted values to be calculated. As a simple bio-indicator
technique for regional spatial comparison, the method has severe
limitations since many other factors affect species composition.
However, the method is well suited to assess local spatial changes
near sources, as well as to long-term bio-monitoring at fixed
locations. The assessment of lichen floral composition provides a
particularly sensitive approach to indicate atmospheric nitrogen
exposure. However, while the responses to gaseous ammonia are well
characterized, there is more debate regarding the effects of
nitrogen oxides or total nitrogen deposition. The ammonia response
is, to a large extent, mediated by an increase in bark pH, which
selects against "acidophyte" species and favours "nitrophyte"
species. The most sensitive specialist scoring system follows that
of van Herk, while there is also potential to refine a simplified
"Ellenberg"-type approach for use by non-specialists. Lichens on
twigs are found to be particularly sensitive to ammonia due to
their naturally higher bark pH than trunks of trees.
Plant transplant methods can be used both to monitor
atmospheric nitrogen deposition and its impacts. The setting out of
standardized grass plants provides a rapid and graphic
demonstration of atmospheric nitrogen impacts for local site
assessments. For example, plants were shown to grow twice as fast
in the immediate vicinity of a poultry farm compared with 300 m
distant. While shading may affect growth rate and dilution by the
plant, the total N inventory of the plant gives a robust indication
of atmospheric inputs, including the potential to estimate the
saturation of dry deposition rates. Native plant species may also
be transplanted reciprocally between high and low N sites, with
measurement of growth rates and foliar N levels. While further work
is required to improve the approaches for higher plants and
lichens, particular success has been had with bryophytes. The
method is labour intensive, but it has the advantage that, where
transplanting to clean conditions leads to plant recovery, the case
for pollution abatement of an existing source is substantially
strengthened.
It is clear that there are limitations to each of the
approaches for bio-monitoring of reactive atmospheric nitrogen.
However, a number of techniques are now available to indicate
different aspects, such as concentrations, deposition and impacts
of different components of atmospheric nitrogen over different
timescales. Used in conjunction with the classical critical loads
assessment, bio-monitoring therefore provides a practical approach
to demonstrate nitrogen exposure and impacts on statutory nature
conservation sites.
Atmospheric
nitrogen pollution impacts on biodiversity:Phase 1 - Model
development and testing
Dr. Jane Goodwin, Land Use and Rural Affairs Science
Unit, Biodiversity and Landscape Branch Defra
SUMMARY
Emission of pollutants to the atmosphere (e.g. oxides of
nitrogen and ammonia) can lead to levels of nitrogen enrichment
which have adverse effects on vegetation and ecosystem function.
Semi-natural habitats are known to be particularly vulnerable. Two
recently published national monitoring studies have detected signs
of widespread nitrogen enrichment in the British countryside, and
an inter-agency expert panel has highlighted nitrogen enrichment as
a key threat to UK vegetation composition. This work is therefore
being commissioned to investigate the implications of atmospheric
nitrogen deposition on biodiversity. The overall aim is to develop
and test sophisticated analytical techniques in order to assess the
importance of this factor with specific reference to the delivery
of PSA targets for achieving favourable condition on SSSIs and to
Biodiversity Action Plan targets for priority habitats and
species.
AIMS AND OBJECTIVES
This research project aims to build on the results of the earlier
work in order to improve our understanding of nitrogen pollution
impacts on biodiversity. It is anticipated that the work will
proceed in two distinct phases. Phase 1 will include information
review, model developments and testing of the applicability and
validity of the approaches developed. Phase 2 is likely to proceed
according to the relative merits of the work delivered under Phase
1. The objectives for Phase 1 are:
- Review the current knowledge base for atmospheric nitrogen
pollution impacts on biodiversity.
- Further develop and test modelling techniques to help quantify
the impacts of atmospheric nitrogen deposition on biodiversity
nationally.
- Apply the modelling techniques to a sample of habitats and
sites to examine current and projected levels of the nitrogen
threat (from atmospheric and other sources) to habitats and sites
of high nature conservation importance.
- Provide a preliminary interpretation of the results with
respect to achievement of: (i) the Public Service Agreement (PSA)
target for achieving favourable condition on SSSIs; and, (ii)
Biodiversity Action Plan targets for priority habitats and species
and related indicators of biodiversity (e.g. Country Biodiversity
Strategy indicators).
- Develop proposals for Phase 2 of this work which should allow
for a wider geographical application of the models.
The project is in the process of being let as of 23rd October
and if negotiations are successful it should commence by the end of
2003 and run for approximately 18 months. A steering group will be
formed to guide the project.