A new approach for hydrologic performance standards in wetland mitigation

Area of Science:

• Ecological restoration
• Wetland science
• Environmental management

Background:

• Compensatory mitigation for wetlands often fails to replace lost functions or acreage.
• Current wetland restoration performance standards primarily focus on vegetation, neglecting crucial hydrologic regimes.
• Hydrology is widely recognized as fundamental to wetland structure and function.

Purpose of the Study:

• To evaluate the effectiveness of hydrologic performance standards in assessing wetland restoration outcomes.
• To compare water level recovery times across different wetland types using reference sites.
• To determine if hydrologic similarity to reference sites influences vegetation success in restored wetlands.

Main Methods:

• Analyzed water level data from restored and reference wetland sites across the U.S.
• Assessed time required for restored wetland water levels to match reference sites for three wetland types (vernal pools, fens/wet meadows, forested wetlands).
• Correlated water level similarity with vegetation cover (native and exotic species).

Main Results:

• Hydrologic recovery varied by wetland type: vernal pools (9 years), fens/wet meadows (4 years), forested wetlands (1 year).
• Increased water level similarity to reference sites correlated with higher native plant cover across all wetland types.
• In fens and wet meadows, hydrologic similarity was linked to reduced exotic species cover.

Conclusions:

• Hydrologic performance standards offer a meaningful metric for evaluating wetland restoration.
• Matching reference site hydrology can enhance vegetation success, particularly native plant establishment.
• Tailoring hydrologic performance standards to specific wetland types may improve restoration outcomes.