Blue whale’s quiet comeback

Aerial surveys published this month counted more blue whales in the southern hemisphere than any survey has counted in fifty years, and the numbers, which the scientists are careful to describe as estimates, point to a recovery that has been running quietly for a decade. The whales were counted in the waters where the krill is thickest, which are also the waters where the container ships pass, and the coincidence is the point: the region’s new speed rules, introduced to protect the fin whales first, have turned part of the shipping lane into a corridor that the blue whales are using again. The recovery is real, and it is being measured in a way that the oceans have rarely allowed before.

The history of the blue whale is the history of industrial whaling written in the largest possible letters. The species was hunted to the edge of extinction by the middle of the last century, with the southern population reduced to a few thousand from the hundreds of thousands that the whalers logged. The ban on commercial whaling came in time to save the species and too late to save its numbers, and for decades the surveys returned the same discouraging count. The new data does not overturn that history; it measures the rebound that the ban made possible, and the rebound is faster than the models that were built on the old counts.

The methodology is worth pausing on, because it is the reason the numbers can be believed. The survey combines aerial transects with acoustic monitoring, the underwater microphones that hear the whales’ songs from a thousand kilometres away, and the two methods correct each other’s blind spots: the planes count what the microphones cannot locate, and the acoustics count what the planes cannot see. The combined estimate is still an estimate, with a confidence interval that the authors publish honestly, and the honest interval is the best evidence that the recovery is not a statistical artefact. The oceans are finally being counted with instruments rather than guessed at with extrapolations.

The recovery deserves to be read as a lesson in what conservation can achieve when the economics are aligned. The speed rules were resisted for years by the shipping industry, until the data showed that slower ships burned less fuel, that the delay cost less than the insurance risk of collisions, and that the whales’ corridor overlapped the route that the operators were paid to use anyway. The policy that helped the whales was the policy that helped the fuel bills, and the coincidence is the reason it survived the change of governments and the cycles of enforcement. Conservation that has to fight the economy every year eventually loses; conservation that can ride the economy has a chance of winning.

The survey’s authors end their paper with a sentence that the coverage has quoted widely, and it is worth repeating: the recovery is real, and it is also fragile, because the whales’ food, the krill, is moving with the warming seas, and the corridor that the speed rules protect may not be the corridor that the krill occupies in a decade. The comeback is being measured, which is the achievement; the conditions that made it possible are being monitored, which is the caution; and the whales themselves, the largest animals that have ever lived, are doing what they have always done, which is to take the opportunities the oceans offer and to wait out the changes they cannot control. This month, the opportunities were in the shipping lane, and the whales took them.