Approach
This approach is aimed at reducing chemical impacts and degradation of wetlands due to increased extreme precipitation events and warming. Wetlands adjacent to agricultural and urban areas are most susceptible to nutrient inputs from fertilizer runoff, nutrient-rich sedimentation, and municipal-urban pollutants in storm water discharge. Increased drought events can decrease the area of saturated, anoxic substrates in wetlands, reducing denitrification rates and increasing nitrogen exports, especially in watersheds influenced by agricultural runoff and industrial processes. Wetland community types vary with substrate fertility and differ in their capacities to accommodate chemical inputs without undergoing significant shifts in biological composition and structure. For example, wetland systems that formed in conditions of low nutrient availability (i.e., bogs, poor fens) are the most vulnerable to compositional shifts and changes in ecosystem function due to increased nutrient loading via runoff or increased decomposition rates due to warming. Hydrologic change that increases runoff and chemical loading to wetlands may exacerbate existing challenges associated with a legacy of land-use impacts. Nutrient deposition via sedimentation processes can also be addressed using Approach 2.2 (Menu of Adaptation Strategies and Approaches for Non-Forested Wetlands) tactics.
Tactics
- Remove legacy phosphorus from degraded streams and headwater lakes.
- In agricultural areas with drain tiles, create small, precisely positioned "in-line" wetlands along ditches and small streams to intercept and remove nitrogen from drain-tile flows before it enters higher quality wetlands.
- In agricultural areas upstream from wetlands, employ precision agriculture and cover crops to reduce unnecessary nitrogen application.
- Limit algal growth impacts by harvesting algae from surface waters, physically flush and mix waters, apply chemical treatments, apply materials that immobilize phosphorus, or manage water levels to promote macrophytes rather than algal growth.
- Design wetland creations and enhancements to increase the area and duration of soil saturation to improve denitrification rates.
- Install sediment basins to capture nutrients before they enter wetlands and waterways.
- Apply a nutrient management plan that includes limiting manure spreading on frozen surfaces, steep slopes, near streams, or in areas of fractured bedrock/karst and employ manure biodigesters.
- In phosphorus-rich fields that were previously farmed, eliminate tillage and manure application and transition fields to forage and harvest hay twice a year to reduce soil phosphorus over time.
Strategy
Strategy Text
Approaches outlined by this strategy provide managers with adaptation options aimed to sustain or enhance the quality of wetland habitats susceptible to warming waters and reduced water quality. Warmer water increases the rate of algal growth, changes dissolved oxygen levels and water chemistry, increases decomposition rates, and shifts species composition by altering abundance or cover of existing species and encouraging invasion of non-native species. Increased frequency of large storm events resulting in greater runoff may increase heavy nutrient loading. This adaptation strategy applies to managing the quality of all wetland types, but especially mesotrophic wetlands (e.g., poor coastal fens and inland fens) that are maintained by a delicate balance of hydrologic inputs (groundwater, surface water, and precipitation) and ombrotrophic peatlands (e.g., precipitation-dependent bogs). Wetland managers may already focus on protection of water quality in their management activities, as nutrient enrichment and sedimentation are among the leading causes of current wetland degradation. The likelihood of more extreme precipitation events further amplifies the risk of harmful chemical-laden runoff from adjacent land-uses, particularly in agricultural or urban areas. This strategy addresses the additional protection and focus necessary to ensure clean water inputs to wetland areas. Further, management of wetland processes, given changes in climate, has local and global implications, particularly for wetlands known to sequester large volumes of carbon in soils (e.g., peatlands). Reducing excess nutrient inputs that speed up decomposition rates in organic-rich wetlands (e.g., peatlands) can improve long-term sequestration of CO2 in wetland soils and mitigate future greenhouse gas emissions.