Land cover and rainfall interact to shape waterbird community composition

Area of Science:

• Ecology
• Environmental Science
• Conservation Biology

Background:

• Human land cover impacts estuaries via habitat loss and nutrient pollution.
• Increased precipitation events enhance watershed-estuary connectivity, affecting water quality.
• Consequences of altered water quality on top consumers like waterbirds are poorly understood.

Purpose of the Study:

• To investigate how land cover and rainfall variation influence waterbird community composition in Chesapeake Bay.
• To understand the direct and indirect effects of human land use and precipitation on estuarine ecosystems.
• To assess the ecological thresholds in estuarine management.

Main Methods:

• Non-metric multidimensional scaling (MDS) to analyze community composition shifts.
• Structural equation modeling (SEM) to determine relationships between land cover, rainfall, water quality, and waterbirds.
• Comparison of waterbird communities during a drought year (2002) and a high rainfall year (2003).

Main Results:

• Urban subestuaries shifted from mixed to generalist waterbird communities with increased rainfall.
• This shift coincided with a sixfold increase in nitrate-N concentration.
• In wet years, waterbird composition was affected by direct urban development and indirect nitrate-N inputs, especially in urban areas.

Conclusions:

• High rainfall runoff degrades water quality, altering estuarine waterbird community composition.
• The impact of runoff is amplified in urbanized subestuaries.
• Integrating land cover, water quality, and waterbird data is crucial for effective estuarine management and restoration.