Moving Marshes in the Puget Sound
July 30, 2026
The Billy Frank Jr. Nisqually National Wildlife Refuge is tucked southeast of Seattle, among the twisting inlets of the Puget Sound. The Refuge was created in 1974 to protect the Nisqually estuary from further development. In 2008, a major restoration project removed the Brown Farm ditch to restore natural tidal flows to the Nisqually River Delta estuary. Previously, the hundred-year-old old dike and ditch system blocked saltwater tides from reaching the historical marshlands, cutting off vital habitat for juvenile salmon and other wildlife. The above animation, which runs from August 23, 1985 to September 22, 2025, shows the growth of the Nisqually marsh over time.
Coastal wetlands like the Nisqually National Wildlife Refuge protect against flooding and erosion, provide critical habitat for wildlife, and support fisheries. However, these vulnerable ecosystems are in decline worldwide. Yang et al., 2026 reveals that despite decades of regulatory protection against direct human development, U.S. tidal wetlands have experienced a widespread and accelerating net loss of 1,640 km² from 1984 and 2024, primarily due to the decline of tidal marshes. Using nearly four decades of NASA/USGS Landsat data, researchers identified a critical shift in the drivers of this ecological degradation. While chronic stressors like sea level rise caused the bulk of the historical loss (around 60% of total area lost), acute shocks from extreme weather events — such as hurricanes and severe freezes — are now the dominant forces accelerating this decline. Direct human activity accounted for about 4% of total observed losses.
Though the researchers found an overarching trend of wetland decline, they also revealed different patterns of change for different wetland types. For example, the total area of mangroves remained stable over the 40-year study period, but only because climate-driven poleward expansion of salt-tolerant mangrove forest offset massive weather-induced diebacks, masking the ecosystem's growing vulnerability. The researchers used a dense time series model to identify and characterize wetlands, relying on visible, shortwave-infrared, and thermal bands from Landsat.
The rebounding wetlands of the Nisqually National Wildlife Refuge are a success story, but a rare one. Looking to the future, the researchers note that current conservation strategies may be ill-equipped for a future dominated by extreme weather and call for proactive, large-scale, and adaptive restoration efforts to preserve these vital coastal habitats.
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