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This paper combines the world's protected areas (PAs) under the Convention on Biological Diversity (CBD), common classification systems of ecosystem conservation status, and current knowledge on ecosystem responses to nitrogen (N) deposition to determine areas most at risk. The results show that 40% (approx. 11% of total area) of PAs currently receive >10 kg N/ha/yr with projections for 2030 indicating that this situation is not expected to change. Furthermore, 950 PAs are projected to receive >30 kg N/ha/yr by 2030 (approx. twice the 2000 number), of which 62 (approx. 11,300 km(2)) are also Biodiversity Hotspots and G200 ecoregions; with forest and grassland ecosystems in Asia particularly at risk. Many of these sites are known to be sensitive to N deposition effects, both in terms of biodiversity changes and ecosystem services they provide. Urgent assessment of high risk areas identified in this study is recommended to inform the conservation efforts of the CBD., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Increased atmospheric nitrogen (N) deposition is known to reduce plant diversity in natural and semi-natural ecosystems, yet our understanding of these impacts comes almost entirely from studies in northern Europe and North America. Currently, we lack an understanding of the threat of N deposition to biodiversity at the global scale. In particular, rates of N deposition within the newly defined 34 world biodiversity hotspots, to which 50% of the world's floristic diversity is restricted, has not been quantified previously. Using output from global chemistry transport models, here we provide the first estimates of recent (mid-1990s) and future (2050) rates and distributions of N deposition within biodiversity hotspots. Our analysis shows that the average deposition rate across these areas was 50% greater than the global terrestrial average in the mid-1990s and could more than double by 2050, with 33 of 34 hotspots receiving greater N deposition in 2050 compared with 1990. By this time, 17 hotspots could have between 10% and 100% of their area receiving greater than 15 kg N ha−1 yr−1, a rate exceeding critical loads set for many sensitive European ecosystems. Average deposition in four hotspots is predicted to be greater than 20 kg N ha−1 yr−1. This elevated N deposition within areas of high plant diversity and endemism may exacerbate significantly the global threat of N deposition to world floristic diversity. Overall, we highlight the need for a greater global approach to assessing the impacts of N deposition. [ABSTRACT FROM AUTHOR]

In Europe serious problems associated with emissions of nitrogen oxides and ammonia are related to eutrophication and acidification. Impacts of eutrophication in terrestrial ecosystems are associated with changes in floristic composition and in ecosystem function and stability. Various activities have been initiated to assess the risk posed by nitrogen deposition for negotiations concerning the UN/ECE NOx Protocol. As there are difficulties in mapping critical loads for nitrogen, two different methods are presented here at European scale. One method uses a sensitivity approach linked to data for empirically derived critical loads; the other method uses a nitrogen saturation approach which sums quantitative values for acceptable long-termremoval rates of nitrogen from the ecosystem and accumulation in soil organic matter. Resulting critical load maps show significant areasacross Europe that are potentially sensitive to nitrogen deposition.Generally, the spatial distribution of sensitivity shows similarities using both approaches. However, the range of empirical critical loads in the literature determined for certain vegetation types is greater than those calculated using the saturation approach. A comparison with 1990 total nitrogen deposition does reveal a similar distribution of exceedance, but only when the lower end of the empirical critical load range is used. There are uncertainties associated with both methods nevertheless they do illustrate that substantial areas across Europe may be at risk from deleterious impacts caused by nitrogen deposition. [ABSTRACT FROM AUTHOR]