Scientists in South America are studying the recovery of southern right whales after many decades of whaling in the past and ongoing human threats, including entanglement in fishing nets, ship strikes, pollution, anthropogenic ocean noise, and climate change. That they would be threatened by climate change is ironic, given the role these huge animals play in mitigating its effects. Whales do this by providing nourishment for keystone species, notably krill, in their excreta (and, ultimately, their carcasses) and absorbing and sequestering huge amounts of carbon dioxide during their lifetimes. The scientists have analyzed 50 years of data related to southern right whales in the waters off Argentina’s Valdes Peninsula, and have found a marked increase in whale mortality rates following El Niño events. These events are increasingly associated with the warming of the central and eastern tropical Pacific Ocean. The scientists modeled how the right whale population responds to changes in the frequency and intensity of El Niño events in an attempt to gauge how such events are likely to impede population recovery. Given the integral role that southern right whales play in a healthy Southern Ocean ecosystem, such information is key to helping assess the impacts of climate change on marine ecosystems in general.