Sea level rise to whack migratory shore birds

Sea level rise is expected to impact on the habitats of many shore birds. A new analysis is suggesting the impacts may be worse than previously expected for migratory shore species.

Habitat loss is widely used as a measurement of the risk of extinction, but because many coastal species are migratory, the impact of habitat loss to sea level rise will depend not only on its extent, but also on where it occurs. Takuya Iwamura and colleagues have developed a novel graph-theoretic approach to measure the
vulnerability of a migratory network to the impact of habitat loss from sea level rise based on population flow through the network.

They show that reductions in population flow far exceed the proportion of habitat lost for ten long-distance migrant shorebirds using the East Asian–Australasian Flyway. They estimate that sea level rise will inundate 23–40% of intertidal habitat area along their migration routes, but cause a reduction in population flow of up to 72% across the taxa. This magnifying effect was particularly strong for taxa whose migration routes contain bottlenecks—sites through
which a large fraction of the population travels. The researchers develop the ‘bottleneck index’, a new network metric that positively correlates with the predicted impacts of habitat loss on overall population flow. These results suggest that migratory species are at greater risk than previously realized.

Iwamura T, HP Possingham, I Chadès, C Minton, NJ Murray, DI
Rogers, EA Treml & RA Fuller (2013). Migratory connectivity
magnifies the consequences of habitat loss from sea-level
rise for shorebird populations. Proceedings of the Royal Society
B-Biological Sciences. 280: 20130325.

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