In the past decade, an unexpectedly high number of calves have been born to North Atlantic right whales—a species once projected for extinction.
The baby boom is linked to a climate-induced shift in the oceanic ecosystem, one that has improved the feeding conditions for the whales in the northwest Atlantic and especially the Gulf of Maine during the first decade of the 2000s.
Relative to the lean reproductive years right whales suffered during the 1990s, the population during the first decade of the 21st century has seen a significant increase in reproduction, researchers say.
By the late 19th century, the whaling industry had all but killed off North Atlantic right whales, valued for their oil, which was used to burn lamps and lubricate machinery.
The whale population has exhibited a gradual but bumpy recovery since the species gained protected status during the mid-20th century.
Annual surveys of the population since the 1970s have allowed researchers to study right whale population dynamics. During the 1980s, thanks to good feeding conditions, the population exhibited positive growth.
During the early 1990s, the Arctic underwent a decade-long climate shift, resulting in an influx of freshwater into the northwest Atlantic. This “great salinity anomaly” of the 1990s freshened coastal shelf ecosystems in the northwest Atlantic, says oceanographer Charles H. Greene, a professor at Cornell University.
The ecosystem became unfavorable for the copepod species Calanus finmarchicus—the whales’ main source of nutrition. With feeding conditions for the whales especially poor when Calanus suffered a crash in 1998, the whale population, in turn, failed to reproduce in 1999 and 2000.
The subsequent resurgence of Calanus during the 2000s has been linked to a shift in the Arctic climate system back to conditions similar to the 1980s. This “decadal-scale variability in right whale reproduction may be largely driven by fluctuations in prey availability linked to climate-associated ecosystem regime shifts,” the researchers say.
“Rather than facing the prospect of eventual extinction, as was forecast at the beginning of the new millennium, the right whale population in 2010 was on a positive trajectory toward recovery,” the researchers write in the journal Oceanography.
It’s important to note, however, that “continued elevated rates of right whale calf production are contingent upon favorable future prey conditions.”
The National Science Foundation and the Department of Defense supported the research.
Source: Cornell University