Plate Nº 56 · recorded October 8, 2026
Earth & ClimateReported finding
Rising Seas Threaten the World's Migratory Shorebirds
A review of 37 studies offers the first comprehensive picture of how sea-level rise threatens shorebirds, with key stopover sites supporting up to 1 million birds at risk.
By Elena Vasquez3 min read639 words
In brief
- Researchers reviewed 37 published studies on sea-level rise impacts on shorebirds.
- 21 of the studies predicted habitat declines; 17 predicted negative impacts on populations or individuals.
- At-risk bottleneck sites include San Francisco Bay, Humboldt Bay, the Colorado River Delta, Marismas Nacionales and the Yellow Sea.
- Each of these sites supports 150,000 to more than 1 million shorebirds annually.
- More than half of the world's largest cities lie within 100 kilometers of a coast, blocking habitats from moving inland.
A review of 37 published studies has produced the first comprehensive overview of how sea-level rise threatens the world's migratory shorebirds — and the picture, in the researchers' own words, is not good. Of the studies examined, 21 predicted that rising seas will shrink shorebird habitats in area or quality, while 17 predicted direct harm to bird populations, such as lower survival or falling abundance.
The study, published in the journal Biodiversity and Conservation, focuses on shorebirds — a group that includes sandpipers, plovers and oystercatchers — which live and migrate along the world's coastlines. Many of these birds travel hundreds to thousands of kilometers each year between breeding grounds and seasonal feeding areas. Migration is central to their success, but it also concentrates huge numbers of birds at a small number of coastal sites, which makes them unusually exposed to local habitat loss.
What is 'coastal squeeze'?
Shorebirds rely on coastal ecosystems such as beaches, salt marshes and tidal flats. As sea levels rise, these habitats shrink. In theory, some coastal ecosystems could survive by shifting inland as the water moves up. In practice, hard barriers often stand in the way.
More than half of the world's largest cities sit within 100 kilometers (62 miles) of a coast. Dikes, seawalls and other structures built to protect homes and businesses block the inland pathways that ecosystems would otherwise follow. The result is a phenomenon scientists call coastal squeeze: habitats pinned between rising water on one side and human infrastructure on the other, with nowhere to go.
For the birds, the consequences are straightforward. Less habitat means less access to food, less space for nesting and more competition with other individuals. But the study's authors point out that habitat loss is not the only mechanism at work. Sea-level rise may also shift where prey species are found, reduce reproductive success and cut into feeding time, among other effects.
How serious is the threat?
The numbers from the review point to substantial projected habitat loss at several sites of international importance for migratory shorebirds, including:
- San Francisco Bay and Humboldt Bay in the United States
- The Colorado River Delta and Marismas Nacionales in Mexico
- The Yellow Sea region in East Asia
Each of these sites supports between 150,000 and more than 1 million shorebirds annually. That concentration is exactly what makes them so vulnerable — and so consequential. These are migratory bottleneck sites, where enormous numbers of birds pass through over a short period. Habitat loss at a bottleneck can ripple across multiple species and affect entire populations, not just local ones. For that reason, the authors argue, these sites must rank among the highest priorities for conservation.
It is worth noting the limitations of the evidence base. The review synthesizes 37 studies, which makes it the broadest assessment to date, but many of its conclusions rest on projections rather than documented declines. The field is still young, and the full range of impacts — from shifting prey distributions to altered breeding timing — remains an active area of research.
What can be done?
Protecting coastal ecosystems from sea-level rise matters beyond shorebirds. These same ecosystems support thousands of other species and provide services people rely on: coastal protection, water filtration and carbon storage.
The study's authors argue that governments will need to take coastal squeeze seriously rather than continuing to armor shorelines with ever more hard defenses. Solutions will vary by location:
- Managed retreat — relocating coastal infrastructure in some areas to give ecosystems room to move inland as seas rise.
- Sediment reuse — using material recovered from dredging to enhance existing habitats or create new ones.
The common thread, the researchers stress, is urgency. However societies choose to respond to rising seas, action taken now will determine whether shorebirds and their remarkable migrations survive for generations to come.
via Phys.org Biology (Source)
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