Climate-driven range shift reveals systemic ecological disruption: Atlantic mangrove fiddler crab expands into temperate salt marshes

Indigenous coastal communities in the southeastern U.S., such as the Gullah-Geechee, have historically managed mangrove and salt marsh ecotones through sustainable harvesting and fire practices, which maintained ecological balance. Their knowledge of species migration patterns and tidal rhythms could provide critical insights into the crab’s expansion, yet Western science often sidelines these perspectives in favor of data-driven models. The erasure of Indigenous land stewardship obscures a long-standing tradition of adaptive co-management with coastal ecosystems.

During the Holocene Climatic Optimum (~6,000 years ago), mangroves expanded northward along the Atlantic coast as temperatures rose, only to retreat during cooler periods. The current range shift mirrors these prehistoric patterns but is accelerated by anthropogenic warming and coastal development, which fragment habitats and reduce resilience. Historical records from European colonizers in the 18th and 19th centuries document the presence of mangroves as far north as North Carolina, suggesting that the crab’s expansion may represent a partial return to a pre-colonial ecological state disrupted by industrialization.

In Southeast Asia, mangrove-dependent communities have long adapted to species migrations by diversifying livelihoods and integrating new species into cultural practices, such as the use of mangrove crabs in traditional medicine and cuisine. Similarly, in the Caribbean, fishers have observed the northward movement of lobster and conch populations, adjusting gear and fishing grounds to maintain food security. These cross-cultural examples highlight the importance of traditional ecological knowledge in navigating ecological transitions, offering lessons for the U.S. Southeast.

The study’s documentation of the crab’s range shift aligns with broader scientific consensus on marine species migration due to ocean warming, with documented cases of tropical fish and invertebrates moving poleward at rates of 20–50 km per decade. However, the research focuses narrowly on species distribution without addressing the ecological cascades—such as altered sediment dynamics, predator-prey imbalances, or salt marsh die-off—that may accompany this shift. Future studies should integrate physiological, behavioral, and ecosystem-level data to predict long-term impacts on biodiversity and carbon storage.

Artistic and spiritual traditions often frame ecological shifts as part of a living, interconnected system, rather than isolated phenomena. For instance, the Haudenosaunee Thanksgiving Address acknowledges the role of all species in maintaining balance, a perspective that could reframe the crab’s migration as a sign of ecological reciprocity. Similarly, Japanese haiku poetry captures the transient beauty of seasonal changes, offering a lens to appreciate the crab’s expansion as part of a larger, cyclical narrative of nature’s adaptation.

Modeling suggests that by 2050, the crab’s range could extend as far north as Chesapeake Bay, fundamentally altering salt marsh food webs and carbon sequestration rates. Scenario planning must account for feedback loops, such as increased predation on salt marsh grasses by crabs, which could reduce habitat for migratory birds like the red knot. Additionally, the expansion may outpace the adaptive capacity of temperate species, leading to novel ecosystems with unknown biodiversity outcomes. Policymakers should prepare for these shifts by designating flexible marine protected areas and investing in assisted migration strategies.

Marginalized communities in the southeastern U.S., including African American shellfish harvesters and Indigenous groups like the Lumbee, are disproportionately affected by habitat loss and species displacement but are rarely consulted in scientific or policy discussions. Their traditional knowledge of coastal ecosystems could inform adaptive management strategies, such as restoring oyster reefs to buffer against erosion or reintroducing fire to maintain salt marsh health. Centering these voices is essential for equitable climate adaptation and ensuring that solutions do not exacerbate existing inequalities.