Vultures have an image problem. Charles Darwin did them no favors when he saw a turkey vulture from the deck of the Beagle in 1835 and called it a “disgusting bird” whose bald head was “formed to wallow in putridity.” Despite their vital cleanup role, vultures are not nearly as cute as polar bears, nor do they inspire the same interest when extinction looms—as it does for more than half of the world's 23 vulture species.

In Asia, livestock carcasses laced with the painkiller diclofenac wiped out 95 percent of three vulture species in just 15 years before nations began banning the drug in 2006. African vultures are vanishing just as rapidly. A study in 2012 reported up to 33 percent annual mortality rates for some species in East Africa. The crisis spurred the first Pan-African Vulture Summit last year, but political action has failed to materialize.

“A Kenya Wildlife Service scientist recently told us, ‘We are so busy trying to save elephants and rhinos, when it comes to vultures we are just tired,’” says Darcy Ogada of the nonprofit Peregrine Fund. Ogada and her colleagues have documented staggering die-offs: in rural West Africa, for instance, populations of almost all vulture species have fallen by 95 percent in 30 years.

Saving African vultures will require more than a simple drug ban. In East Africa, vultures are both targets (slaughtered by ivory hunters to conceal poaching sites) and collateral damage (poisoned by pastoralists out to kill livestock predators, such as hyenas and lions). In West Africa, vulture parts are sold as meat or as clairvoyance drugs in the indigenous medicine trade. Wind farms and electrical lines pose growing additional threats.

As the vulture die-off continues, raptor specialists assess the consequences. In India it seems to have sparked population booms for rats and feral dogs, which carry leptospirosis and rabies. Ecological economists estimate the health-associated costs from India's dearth of vultures at $34 billion over 14 years. African vultures consume carcasses of livestock and migrating wildebeests, breaking down pathogens such as anthrax in the process. “If they were gone, we'd be left with a huge disease-transmission time bomb,” says Munir Virani of the Peregrine Fund.

For her part, Ogada is now developing ways to track the spread of carrion-borne disease. By quantifying the public health cost of the vulture die-off, she hopes to spur governments to do something about it.