03/11/2013 02:21 pm ET Updated May 11, 2013

In East Africa: Empty Skies

Mpala Research Centre, Kenya -- I am back in East Africa for the first extended time since completing my graduate research 30 years ago. It's a hugely exciting time to be working with our staff in shaping larger conservation efforts with vultures, flamingos, and African Grey Parrots. Between office and field visits, I witnessed for the first time the most dinosaurian of all living birds: the improbable Shoebill stork.

In my first years in Kenya, it was pointed out how you couldn't look up in the sky and not see birds of prey. I scanned the skies often in those days, never failing to verify that observation. There were augur buzzards, Bateleurs, African fishing eagles, etc., and lots of vultures of several species. Tropical America may have the most species of birds, but savannah East Africa has the most conspicuous diversity of birds in the world. The skies held part of that diversity, yet it is there that I observe the greatest change in the decades since I was last here.

The skies are more often empty now. In particular, the skies are emptying of vultures. Those iconic birds -- which clean the large carcasses of the antelopes, zebras, and other prey of predators like the lion and hyena in this singular part of the world -- are in steep decline. The vultures are in harm's way, caught in the growing human and livestock conflicts in a rapidly changing Africa. They are being poisoned with the lions and hyenas as the distinction between park and livestock grazing habitat blurs.

Depredated livestock carcasses are now often poisoned with cheap and available insecticides and other poisons, with the intent to kill the carnivores. Vultures naturally crowd carcasses in large numbers and so suffer large losses. In Uganda, at Queen Elizabeth National Park, WCS has worked with villagers to provide more water for their livestock, reducing the need to move livestock into the park. We must grow that model to help vulture (and lion and hyena!) populations recover even more widely in East Africa and beyond.

In fact, it is a world of poisonous trouble for vultures. In India and Nepal, vulture populations have collapsed by 90 percent in the past decade. There, the poisoning is unintentional. Diclofenac, an affordable drug given to farmers to boost the health of cattle, has proved fatal to vultures who scavenge the cattle carcasses. In the United States, efforts to restore the California condor have been repeatedly stymied by the condors' feeding upon carcasses of animals shot by hunters. Lead in unretrieved bullets is to blame as well in the poisoning of the iconic Andean Condor, which is now disappearing.

It is a poisonous world. Some 50 years ago Rachel Carson heroically highlighted how our use of DDT had led to thinner, more vulnerable egg shells in our bald eagle, peregrine falcon, osprey, and other species. Our American skies were emptying then. Today our skies -- including mine around Portland, Ore. -- are filled once again with those species because we took action against DDT. And yet worldwide, our skies are emptying of vultures and other life as the poison continues.