Salt marshes are coastal wetlands that are flooded and drained by tides. These ecosystems occur along temperate shorelines worldwide. Tidal inundation occurs every twelve hours, flooding the habitat with higher tides around the new and full moons every two weeks. These intertidal habitats are an essential space for healthy wildlife communities, including some species that are perfectly adapted to their unique, salty ecology.
Meet the Saltmarsh Sparrow: This small, ground-foraging bird lives exclusively in salt marshes on the U.S. east coast, where they breed in tall cordgrasses and build nests that are regularly flooded by tides. That doesn’t sound like an ideal nursery spot, but Salty Sparrows are uncommonly tailored to this lifestyle.
While most sparrows in the family Passerellidae, or “New World” sparrows, are monogamous and both parents care for young, Saltmarsh Sparrows are not quite as… devoted. These birds don’t show signs of competing for mates, almost every brood has mixed parentage, and studies indicate that male birds don’t even know where nests are. When your nests could be flooded at any time, there’s no time to wait around. Females’ nesting behavior is highly synchronized with lunar tidal cycles, allowing them to have much lower rates of nest flooding than similar species.
Unfortunately, these birds and a number of other species that reside in salt marshes are in danger. Coastal wetlands are critical ecosystems–despite only making up around 10% of Earth’s land area, they support a quarter of the human population–but they have been heavily degraded by infrastructure development, invasive species, and sea level rise.
What does this mean for a species like the Saltmarsh Sparrow, who occupy a highly specific niche within coastal ecosystems? That narrow margin for error just got a little bit thinner.
The U.S. Fish and Wildlife Service (USFWS) estimates that the total population has been reduced by around 87% since 1998, from over 210,000 individuals to a little over 28,000. Saltmarsh Sparrows have experienced significant losses due to nest failure. Nests fail mainly due to flooding carrying eggs away, but this threat is coupled with others:
- Encroachment of invasive grasses that are less suitable for nesting
- Increased exposure to nest predators
- Fragmentation of salt marshes reducing habitat patch size, directly correlated with abundance
Marsh restoration projects have focused on preserving the ecosystem services that wetlands provide (carbon sequestration, water filtration, storm surge protection, fisheries support and more). Less prioritized is the preservation of biodiversity, and particularly endemic species like the Saltmarsh Sparrow.
In the United States alone, tens of thousands of hectares of salt marsh have been restored, with a price tag in the range of thousands of dollars per hectare. Many restoration projects focus on altering hydrology or vegetation through direct management or installation of man-made structural components, but this can have negative impacts on species. For example, projects that restore tidal flow are usually considered successful if they return native plants to their place and control invasives, but some studies show that they result in increased nest flooding for birds like the Saltmarsh Sparrow.
The restoration of salt marshes is ongoing around the world, but the quality of habitat for sensitive species like the Saltmarsh Sparrow likely takes place on the order of decades, not years.
On Earth Day of this year, the Center for Biological Diversity submitted a petition to USFWS to protect the Saltmarsh Sparrow under the Endangered Species Act. This would provide protections at the federal level for individual birds and their habitat, both of which are facing numerous compounding threats to their resilience. This decision has been continually delayed, but researchers at the Saltmarsh Habitat and Avian Research Program (SHARP) and the Atlantic Coast Joint Venture are working hard to protect these habitats and the species they support at a state and regional level.
N-EWN partners are among the worldwide community of researchers working to protect biodiversity and ecosystems. Read more on how we’re working to better incorporate biodiversity into coastal infrastructure decisions:
- Embracing biodiversity on engineered coastal infrastructure through structured decision-making and Engineering With Nature® (U.S. Army Corps of Engineers, University of Georgia)
- Jointly advancing infrastructure and biodiversity conservation (U.S. Army Corps of Engineers, University of Georgia)
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