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Wetlands as Sinks for Reactive Nitrogen at Continental and Global Scales: a Meta-Analysis
Citation:
JORDAN, STEVE J., J. STOFFER, AND J. NESTLERODE. Wetlands as Sinks for Reactive Nitrogen at Continental and Global Scales: a Meta-Analysis. ECOSYSTEMS. Springer, New York, NY, 14(1):144-155, (2010).
Impact/Purpose:
The purpose of this study was to quantify reactive nitrogen removal by wetlands at the largest spatial scales, and to examine factors that might modify or control the rates of removal.
Description:
Wetlands perform physical and ecological functions that can result in valuable services to society and human well-being, including removal of reactive nitrogen (Nr) from surface water and groundwater. We compiled and analyzed published data from wetland studies worldwide to estimate total Nr removal and to evaluate factors that influence removal rates. Our results combine data from five general types of wetlands, coarsely classified as freshwater marshes, saltwater marshes, forested wetlands, agricultural wetlands, and “other” (e.g., experimental, mixed, and unclassified) wetlands. The data spanned a range from very small-scale experimental wetlands to vast natural wetland complexes. Ranging over several orders of magnitude in area and Nr loading rates, there was a strong positive linear relationship between Nr removal and Nr loading. Other factors, including absolute latitude, hydraulic loading rate, and tidal influence had minor or non-significant relationships with Nr removal rates and efficiency of Nr removal. We estimate that total Nr removal by major classes of wetlands in the contiguous U.S. is 5.8-6.1 Tg/y, equal to 20-21% of the total anthropogenic load of Nr to the region. Worldwide, rough calculations indicate that Nr removal by the same suite of wetland types is on the order of 26 Tg/y, respectively 11%, 17%, and 7% of natural, anthropogenic, and total Nr inputs. The estimated historical loss of 50% of native wetland area in the U.S. and globally suggests an equivalent loss of Nr removal capacity. Expanded protection and large-scale restoration of wetlands should be considered in strategies to re-balance the global nitrogen cycle and mitigate the negative consequences of excess anthropogenic Nr loading.
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Wetlands as Sinks for Reactive Nitrogen at Continental and Global Scales: a Meta-Analysis