Climate Change Prominent in the Fish & Wildlife Service’s Decision to Protect the Red Knot Shorebird
The U.S. Fish and Wildlife Service released its final rule on December 11, 2014, designating the rufa subspecies of the red knot (Calidris canutus rufa), a small migratory shorebird, as threatened under the Endangered Species Act (ESA). The rufa red knot is particularly well-known for the exceptional range of some of its migratory routes, with birds traveling up to 18,000 miles annually. From the bird’s breeding grounds in the Canadian Arctic, rufa red knots migrate to wintering grounds in the southeastern and Gulf of Mexico regions of the United States, northern Brazil, and the part-Chilean and part-Argentinian archipelago at the southern-most tip of South America known as Tierra del Fuego.
Of particular interest in the Service’s listing decision was its focus on how climate change is harming several aspects of the bird’s nesting, feeding, and migration behaviors, both in the Arctic and in stopover and wintering locations half a world away from the snowy tundra:
- Habitat loss from rising sea levels and subsequent development. As the rufa red knots make their way between nesting and wintering grounds, they use key staging and stopover areas to rest and feed in preparation for the next legs of their journey. The shorebirds use tidal mudflats, salt marshes, peat banks, and other exposed intertidal areas where they feed on mollusks, marine worms, horseshoe crab eggs, and other prey. With sea levels rising, the Service projected that coastal communities will continue to build seawalls, jetties, and other “hardened” structures to stabilize and protect shorelines and coastal development. The loss of this foraging habitat impairs the birds’ ability to build up the energy stores they need for their long migrations.
- Habitat loss from Arctic warming. The rufa red knot nests in the Canadian Arctic tundra. The Service found that warming Arctic temperatures make these breeding grounds shrubbier and less suitable for shorebirds. The Service also found that Arctic warming affects the snow conditions, food sources, and predator controls that nesting birds need to raise chicks in the Arctic. For example, the Service noted that warm temperatures are causing insects to hatch earlier, and rufa red knot chicks may miss the peak window for feeding and rapid growth before their first southward migration.
- Climate-driven mismatches between the bird’s arrival time at migratory stopover locations and the peak availability of food. The rufa red knot generally times its migration to coincide with specific food sources at its stopover and refueling locations. The Service cited Delaware Bay and its horseshoe crab eggs as an example of climate change leading to timing mismatches in some years. In one scenario, warmer coastal waters may cause horseshoe crabs to lay their eggs earlier, before the arrival of the rufa red knot. In a different scenario, more intense and frequent coastal storms may cause the crabs to lay their eggs after the red knots have departed. The Service also found that ocean acidification and warming interferes with another food source, mussels and clams. Ocean acidification affects clams’ and mussels’ ability to form shells, and warming water affects their geographic distribution and spawning periods during times when the red knots rely on them as a food source.
- Potential increases in predation in the Arctic breeding grounds. The Service noted that Arctic predators—such as falcons, owls, jaegers, foxes, and wolves—typically prey on rodents, but that during years of small rodent populations, they turn to prey on rufa red knot eggs and chicks. Although the Service emphasized that this natural cycle is not a threat to the bird, the disruption of this cycle from climate change is. The Service explained that warmer temperatures and changes in vegetation have, in some areas, led to the collapse of rodent populations, which has then shifted pressure onto the rufa red knot eggs and chicks.
In discussing its rule, the Service adopted the Intergovernmental Panel on Climate Change (IPCC) definition of “climate change.” Under that definition, climate change means the long-term changes in climate measures (such as temperature and precipitation), whether due to natural variability, human activity, or both. The Service also credited IPCC’s conclusions that the warming of the global climate system is both unequivocal and accelerating, with temperatures in the Arctic increasing about twice as fast as in middle latitudes. The Service also discussed how some of these harms to the bird are attributable to potential changes in storm and weather patterns.
The Service’s consideration of climate change effects on Arctic species is not new or unusual. For example, when the Service listed the polar bear as threatened in 2008, it focused heavily on climate change and the loss of sea ice habitat. The Service’s cited effects from climate change on the rufa red knot, however, are not nearly so localized as those that faced the polar bear. Indeed, as the final rule demonstrates, the breadth of the Service’s effects inquiry for climate change reaches across large swathes of the species range and migratory routes.
The rufa red knot listing may signify an emerging shift toward the Service’s comfort in making climate-based listing decisions. One indication is how differently the Service portrayed the use of climate change effects surrounding its 2008 polar bear listing decision. At that time, the Service prominently emphasized in Frequently Asked Questions that the ESA was not an effective tool to regulate climate change or to set climate change policy. In similar Questions and Answers for the rufa red knot, the Service provides no similar acknowledgement. This could signify the Service’s belief that given the ubiquity of climate change discussions in the public arena, a climate-based listing decision no longer requires a policy explanation.
Although the rufa red knot listing decision may be notable for its extensive consideration of climate change effects on several aspects of the bird’s nesting, feeding, and migration behaviors, it seems unlikely that the Service would shy away from climate-driven effects even if they were not quite as dramatic. The public is unlikely to have to wait long to see whether this is true and whether climate-driven listings are now part of the Service’s ordinary course of business. The Monarch butterfly, the white-tailed ptarmigan, the Bicknell’s thrush, and a host of other species with particular threats from climate change are at various stages of the listing process before the agency, and we will soon see how significant a shift is underway.
Posted by Brandon Tuck
at 12/16/2014 2:25 PM