Geographical variation in hurricane impacts among sea turtle populations
Hurricanes bring wind and rainfall that can have dramatic effects on coastal ecosystems, which provide important nesting locations for some migratory species. We investigated the frequency with which hurricanes impact spatially and biologically distinct sea turtle nesting populations to understand whether the reproductive biology of sea turtles can buffer population-level impacts of these disturbances.
North-western Atlantic and north-eastern Pacific Oceans.
Historical hurricane paths from 1970 to 2007 were combined into a spatial layer of seasonal storm frequency, which we used to quantify the frequency of impacts on sea turtle nesting sites. This was done by comparing spatio-temporal patterns of hurricane frequency among nesting sites used by different species and spatially/biologically distinct populations (‘regional management units’).
Hurricanes affected 97% of sea turtle nesting beaches (n = 2444) over four decades, and the seasonal incidence of these storms overlapped substantially with sea turtle nesting and egg incubation periods. The spatial distribution of storms, in relation to the distribution of species and regional management units, determined relative exposure to large storm events. Green (Chelonia mydas), hawksbill (Eretmochelys imbricata) and leatherback (Dermochelys coriacea) turtle nesting beaches experienced relatively frequent storms; loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii) turtle nesting beaches experienced relatively fewer storms; and olive ridley turtle (Lepidochelys olivacea) nesting sites were least affected.
Extreme weather events are common features of coastal environments and may impact sea turtles by altering nesting habitat quality (through sand erosion and accretion) and lowering within-season reproductive success by drowning incubating embryos or eroding nests. The unique reproductive attributes of sea turtles (i.e. individual females reproduce at 2–5-year intervals, and when reproducing lay 2–7 clutches of c. 100 large eggs at c. 2-week intervals) may be uniquely suited to exploiting highly disturbed nesting habitats. The impacts of hurricanes on sea turtle populations may be limited because even in severe storm seasons only a proportion of adult females are reproducing, and only those eggs incubating at the time of storm impact will be directly affected. Understanding whether the frequency of large storms influences long-term population dynamics will aid in the development of effective local and regional management plans for sea turtle recovery efforts.