Researchers noted that populations have not declined by 56 percent across the board. "What's left now is sort of islands of gorillas and chimpanzees and other areas where they've been wiped out completely," said Walsh.
The survey noted that ape densities declined by 99 percent in the Minkébe forest of northern Gabon in the last decade. Ebola was the likely cause.
"It's mind-boggling how bad this news is," John Robinson, a senior vice president of international conservation programs with Wildlife Conservation Society, said in a news release.
Guns and Guards
Habitat lost to logging and agriculture once posed the greatest single threat to great apes in Africa. But commercial hunting and Ebola have leap-frogged to the fore in recent years.
Africa confronts a growing crisis in the bush meat trade. Commercial hunters using snares and guns strip an estimated one million tons of wildlife from forests to supply logging camps and distant cities with smoked bush meat. Trade has grown into a U.S. $1 billion-a-year industry.
While Gabon does have a crack, national anti-poaching team, it is too small and under funded to grapple with the scope of the country's bush meat problem, Walsh said. To intervene effectively, arming park guards, conducting regular anti-poaching patrols, establishing road blocks and vehicle searches, and searching trains and airlines for smuggled bush meat are necessary steps, Walsh said.
Other wildlife experts agree. "I think there are many different solutions, not just guns and guards. But that's also part of it," said Kormos, a great ape expert who has spent five years working in Gabon and Equatorial Guinea. "Because at the end of the day you have to make a decision. If these species are really going to disappear because of bush meat hunting, well sometimes fairly strong actions are needed."
While controversial, similar law enforcement measures have proven effective elsewhere in Africa. In the 1980s the Kenyan government armed Kenyan Wildlife Service guards with semiautomatic G-3 rifles and shoot on sight authority to battle ivory poachers who killed close to 80 percent of the country's wild elephants and black rhinos in just two decades. Tanzania, Botswana, Namibia and, more recently, the Central African Republic have enforced similar programs.
Meanwhile, commercial logging companies still routinely cut inside park boundaries in Gabon, Walsh said. Enforced park borders, park management plans, budgets, and other protected area management strategies are needed, he said.
National park systems and wildlife agencies in many African countries often lack basic resources to deal with complex problems facing them. "They're highly underfunded. Park guards have very little resources, very little training. And conservation staff from international conservation organizations often can't provide the support that they need to," said Kormos.
How to intervene in the Ebola outbreak sweeping through great apes in the region poses a thornier issue.
An outbreak in Gabon a decade ago may have killed thousands of gorillas and chimpanzees, according to the Wildlife Conservation Society.
The latest epidemic, most visible in Congo's Lossi sanctuary and now approaching gorilla-dense Odzala National Park, has spread like wildfire through 100,000 square kilometers (38,600 square miles) and shows no sign of slowing down, according to Walsh.
The crisis has highlighted some disagreement within scientific circles as to the origins and true nature of the Ebola epidemic and what steps, if any, can be taken to arrest its spread.
Scientists are still seeking answers to such basic questions about where Ebola hides, how is it transmitted, and whether growing incidents of the disease is the result of human ecological change, as most commonly believed, or a spatial epidemic.
Those answers will ultimately determine what course of action to take. Is there little to do but watch disease burn itself out? Or can more aggressive measures, such as constructing epidemic "firebreaks" along rivers and roads, developing vaccination programs, relocating healthy animals, and culling the reservoir hosts of the virus, be taken?
Walsh and other paper authors demand that U.S. $10 million be immediately added to the budget of the U.S. Fish and Wildlife Service Great Ape Fund for Ebola research and prevention.
They've also requested that the World Conservation Union upgrade western gorilla and common chimpanzees from "endangered" to "critically endangered" status.
Top researchers in human and ape Ebola met late last month in Brazzaville, Congo, to discuss the unfolding crisis. A second meeting hosted by Conservation International will be held in Washington, D.C. late next month.
"The idea that this is just a bunch of crazy environmentalists who only care about gorillas and chimpanzees is misplaced," said Walsh. "Our ability to understand the ecological dynamics of emerging disease is absolutely fundamental to preventing those emerging diseases from devastating humans, both in the remote places in the developing world and in the developed worldUnited States underlined."
A summary of the research appears in the current online edition of the science journal Nature.
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