( B) Example of aerial imagery used to track the fate of 111 oyster reefs over 82 y and quantify mangrove establishment, expansion, and conversion at subdecadal intervals ( SI Appendix, Table S1). Insert shows location of Tampa Bay in relation to Cedar Key, FL, the putative poleward range limit for Rhizophora mangle along Florida’s west coast in 2020. Climate records used in this study were obtained from local weather stations across Tampa Bay, and are indicated in A with points. ( A) Map showing the location of three study areas within Tampa Bay: Cockroach Bay (CB), Kitchen Bayou (KB), and Weedon Island (WI), displaying dynamics of oyster reef–to–mangrove regime shifts. Oyster reef–to–mangrove regime shifts from 1938 to 2020 in Tampa Bay, FL. We also show that such climate-driven regime shifts will alter subtropical estuarine landscapes by the end of the present century and discuss implications of cascading regime shifts for coastal management.įig.
West coast sand and gravel driver#
Here, we document how the release from extreme winter freezes, a well-established macroclimatic driver of the salt marsh–to–mangrove regime shift ( 16– 18), also propagates a spatially adjacent regime shift by which oyster ( Crassostrea virginica) reefs are replaced by red mangroves ( Rhizophora mangle) to create forested islands. To date, such interactions remain largely conceptual but pose threats for rapid, landscape-wide ecological change ( 14). With ecosystems closely coupled to macroclimate, it is anticipated that climate change will propagate multiple tipping dynamics or cascading regime shifts, where one climate-induced regime shift triggers another due to interactive elements ( 12– 15). Although it will become increasingly difficult to maintain extant oyster habitat with tropicalization, restoring oyster reefs in high-exposure settings or active removal of mangrove seedlings could slow the coupled impacts of climate change shown here.Ĭlimate change threatens to propel an increasing number of ecosystems across critical transitions this century ( 7–9), as temperature influences core ecological processes across scales and is global in reach ( 9– 11). Climate projections near the mangrove range limit on the Gulf coast of Florida suggest that regime shifts will begin to transform subtropical estuaries by 2070 if propagule supply keeps pace with predicted warming. Coupling of regime shifts arises from the growing supply of mangrove propagules from preceding and adjacent marsh-to-mangrove conversion.
West coast sand and gravel drivers#
Additional nonclimate-mediated drivers of ecosystem change were also identified, including oyster reef exposure to wind-driven waves. Rapid transition occurred following release from freezes below the red mangrove ( Rhizophora mangle) physiological tolerance limit (−7.3 ☌) and after adjacent marsh-to-mangrove conversion. In situ assessments of mangrove islands suggest substantial changes in ecosystem structure during conversion, while radiocarbon dates of underlying reef formation indicate that such transitions are abrupt relative to centuries-old reefs. Using aerial imagery spanning 82 y, we found that 83% of oyster reefs without any initial mangrove cover fully converted to mangrove islands and that mean (± SD) time to conversion was 29.1 ± 9.6 y. Here, we demonstrate that the climate-driven salt marsh–to–mangrove transition does not occur in isolation but is linked to lesser-known oyster reef–to–mangrove regime shifts through the provision of mangrove propagules. Ecological regime shifts are expected to increase this century as climate change propagates cascading effects across ecosystems with coupled elements.
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