High-resolution tide projections reveal extinction threshold in response to sea-level rise.
Sea-level rise will affect coastal species worldwide, but models that aim to predict these effects are typically based on simple measures of sea level that do not capture its inherent complexity, especially variation over timescales shorter than 1 year. Coastal species might be most affected, however, by floods that exceed a critical threshold. The frequency and duration of such floods may be more important to population dynamics than mean measures of sea level. In particular, the potential for changes in the frequency and duration of flooding events to result in nonlinear population responses or biological thresholds merits further research, but may require that models incorporate greater resolution in sea level than is typically used. We created population simulations for a threatened songbird, the saltmarsh sparrow (Ammodramus caudacutus), in a region where sea level is predictable with high accuracy and precision. We show that incorporating the timing of semidiurnal high tide events throughout the breeding season, including how this timing is affected by mean sea-level rise, predicts a reproductive threshold that is likely to cause a rapid demographic shift. This shift is likely to threaten the persistence of saltmarsh sparrows beyond 2060 and could cause extinction as soon as 2035. Neither extinction date nor the population trajectory was sensitive to the emissions scenarios underlying sea-level projections, as most of the population decline occurred before scenarios diverge. Our results suggest that the variation and complexity of climate-driven variables could be important for understanding the potential responses of coastal species to sea-level rise, especially for species that rely on coastal areas for reproduction.
Department of Ecology and Evolutionary Biology, Center for Conservation and Biodiversity, and Institute of Biological Risk, University of Connecticut, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA.
Christopher R
CR
Field
Audubon Washington, 5902 Lake Washington Blvd. S., Seattle, WA, 98118, USA.
Trina S
TS
Bayard
Environment and Climate Change Canada, 45 Alderney Drive, Dartmouth, NS, B2Y 2N6, Canada.
Carina
C
Gjerdrum
Vermont Center for Ecostudies, PO Box 420, Norwich, VT, 05055, USA.
Jason M
JM
Hill
Institute for Wildlife Studies, 2327 Kettner Boulevard, San Diego, CA 92101, USA.
Susan
S
Meiman
Department of Ecology and Evolutionary Biology, Center for Conservation and Biodiversity, and Institute of Biological Risk, University of Connecticut, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA.
Chris S
CS
Elphick
D000818:Animals; D002980:Climate; D057231:Climate Change; D055868:Floods; D005544:Forecasting; D009792:Oceans and Seas; D011157:Population Dynamics; D012098:Reproduction; D012621:Seasons; D020308:Songbirds
extinction threshold; population viability; saltmarsh sparrow; sea-level rise; tidal marsh; tide projection