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An international team of scientists announced to the world last month that they have traced the origin of HIV-1, the virus that causes AIDS in humans, to a subspecies of chimpanzees found in the rainforests of Africa.
The scientists, led by University of Alabama at Birmingham scientist Dr. Beatrice Hahn, expressed hope that their discovery will eventually lead to the development of effective treatments for the AIDS virus, and possibly to the development of a cure or vaccine. The scientists also expressed their concern about rainforest destruction and the "bushmeat" trade, two factors which are pushing the chimpanzees infected with the virus to the brink of extinction.
The virus was discovered in a chimpanzee subspecies called Pan troglodytes troglodytes which is native to the old growth rainforests of Cameroon and Gabon. Although the scientific community had already suspected that HIV-1 came from chimpanzees, no one had been able to identify the precise subspecies until now. Dr. Hahn and her team of scientists, who presented their findings at the Sixth Annual Conference on Retrovirus and Opportunistic Infections in Chicago, believe that the virus may have been transmitted to humans through exposure to the blood of chimpanzees either during hunting or during the handling of chimpanzee meat.
Perhaps the most important aspect of the discovery is that the chimpanzees--who are ninety-eight percent genetically identical to humans--are apparently able to live with the virus without becoming sick. This gives researchers a strong reason to believe that further study of the biological differences between chimpanzees and humans, as well as further study of the ecology of the chimpanzees' rainforest habitat, will result in the development of ways to prevent or treat the AIDS virus.
The National Institute of Allergy and Infectious Diseases has already pledged to finance additional research on the simian virus. One aim of the research would be to determine whether the different outcomes of infection in humans and chimpanzees result from tiny changes in the genetic makeup of the virus or the host. Another aim would be to determine why the chimpanzee's immune system appears to resist the damaging effects of the AIDS virus while the human's is susceptible.
Unfortunately, the wild population of chimpanzees needed for study is being pushed to the brink of extinction by a dramatic increase in the commercial bushmeat trade. Whereas hunters in Cameroon and Gabon once hunted only for food to feed their families, they are now slaughtering forest animals in record numbers in order to sell them for profit in the bustling bushmeat trade. The slaughtered bushmeat animals, including chimpanzees, gorillas, and monkeys, are sold whole or in pieces, smoked or fresh, as food for human consumption. In addition to pushing some forest animals to the brink of extinction, scientists worry that the bushmeat trade may also be putting people at risk of continuing cross-species transmission of known, and unknown, viruses.
The logging industry has played a large part in the proliferation of Africa's bushmeat trade. By building a maze of logging roads into the heart of Africa's old growth rainforests, logging companies are allowing hunters easy access to previously impenetrable forest areas. The easy forest access provided by logging roads has turned the subsistence hunting of bushmeat into a full-scale commercial venture. Some logging companies also actively participate in the bushmeat trade by transporting the hunters and their catch between forests and markets in logging trucks, and by supplying hunters with guns and ammunition. According to Randy Hayes, president of Rainforest Action Network, "It is the logging that is at the core of the problem. We would not have this dramatic increase in bushmeat death and destruction if it weren't for the commercial logging industry."
When Dr. Hahn learned that the natural habitat for the chimpanzees infected with HIV-1 was West and Central Africa, where HIV-1 was first identified, it led her to investigate hunting practices in the region. During her research, she learned about the incursion of roads into remote forest regions, mainly for logging trucks, and the resulting rise in the bushmeat trade. Dr. Hahn has now taken the unusual step of joining environmentalists in publicizing the importance of saving the chimpanzees and their rainforest habitat.
Africa has already lost sixty-five percent of its original forest cover, with almost twenty percent of Africa's tropical forests cleared between 1960 and 1990 alone. With the knowledge that these forests hold the key to a better understanding of the HIV-1 virus, the need to protect Africa's remaining old growth rainforests is clearer, and more urgent, than ever.
With 168 birds on the list of the world's most critically endangered creatures-and many of them from remote, inhospitable places--researchers cannot say for sure which species is the rarest. But that dubious distinction may belong to the po'ouli (pronounced "poh-oh-U-lee"). This Hawaiian honeycreeper, whose name means "black-faced," survives only in a few hundred acres of nearly impenetrable rain forest on the windward side of Maui's Haleakala Crater. At last count, the known po'ouli population was six. And with time running out, experts are scrambling to find a way to save the species from extinction.
If they do succeed, chances are good that Tonnie Casey will be the one who flies to the rescue--literally, at the controls of a Huey helicopter dropping poison bait to eliminate the rats that overrun po'ouli habitat. A biologist for Hawaii's largest private landowner, Kamehameha School's Bishop Estate, Casey has a vested interest in the po'ouli's survival: She was the bird specialist who discovered the species in 1973 while working with college students on an ecological study of what is now the state's Hanawi Natural Area Reserve. But when Casey returned to her native Hawaii after a couple of peripatetic decades that included a long stint of flying choppers for the U.S. Army, she found that the bird had virtually disappeared in her absence.
Black and Pacific rats, which arrived long ago in the Hawaiian Islands as stowaways, have been implicated along with mosquito-borne disease, habitat loss and forest degradation by feral pigs in the extinction of other endemic honeycreepers. At least 11 species have disappeared since the explorer Captain James Cook dropped anchor there in 1778, and another 16 are on the world threatened list, compiled by the IUCN-World Conservation Union.
Mostly forest birds, the honeycreepers evolved from an unidentified finch ancestor into dozens of species. All of them are defenseless against the nocturnal, tree-climbing rats, which raid nests and kill the adults.
"I believe that we can save the po'ouli if we follow New Zealand's example--and do it quickly," says Casey, who is also commander of the National Guard helicopter unit at Hilo, Hawaii. "They've had success using aerial drops of toxicants to create rat-free island sanctuaries for threatened native birds."
New Zealand's spectacular rescue of the Chatham Islands black robin, when only five individuals were left, offers another ray of hope for the po'ouli. Actually a flycatcher rather than a thrush like its American and European namesakes, the black robin was a common bird throughout the remote Chathams group until colonists arrived with cats and rats and cleared most of its scrub habitat. Researchers moved the last survivors to a safe island, manipulated the number of eggs that the black robins laid and enlisted related birds as foster parents. Robin numbers have grown to more than 200.
Biologists at the U.S. Interior Department's Pacific Island Ecosystems Science Center in Hawaii have favored a similar hands-on approach to saving the po'ouli. The plan is to find a nest and move the first clutch of eggs to the Peregrine Fund's new captive breeding facility on the island of Hawaii, where workers have reared and successfully released some common native forest birds and are now experimenting with a few endangered species that are not nearly as scarce as the po'ouli.
However, an intensive search for a po'ouli nest last spring came up empty-handed. Moreover, the Peregrine Fund itself is reluctant to accept po'ouli eggs. "We need more experience with other insectivorous honeycreepers before exposing po'ouli to the risks of egg transport, hand-rearing, imprinting and release," says William Burnham, the organization's president. "We can't afford even one mistake." Aggressive rat control, not captive breeding, is the best conservation strategy, he insists.
Wildlife workers currently use poison bait stations to kill rats, mongooses and other pred- ators in po'ouli habitat. But getting government approval for a helicopter broadcast of an effective rodenticide has been a slow process, in part because state officials fear a public backlash. Authorities want more studies. But, says Burnham, "We needed to do it months ago, before the start of this year's nesting season."
At the center of this tempest is the po'ouli, a stub-tailed bird about the size of a large chickadee and cryptically colored in shades of brown except for its black mask, which is unique in the honeycreeper clan. The po'ouli lives just below timberline on the 10,023-foot volcano in elfin forest, where the limbs of ohi'a lehua trees are wrapped in epiphytic mosses, lichens and ferns and the vegetation is saturated by as much as 550 inches of rain a year. Scientists hope that a few more po'ouli might survive in the lower and most inaccessible part of the Hanawi preserve.
Very little is known about po'ouli biology. Observers have watched the birds hop along tree limbs, tearing apart epiphytes and loose bark with their finchlike bills in search of snout beetles, spiders and other invertebrate prey. They also eat a lot of native land snails. The po'ouli nest is an open cup on a ohi'a lehua branch. The bird's clutch size apparently is two, although no one has ever seen intact eggs.
When Tonnie Casey made her startling discovery 24 years ago, the po'ouli population may have numbered in the hundreds. Although surveys in the mid-1980s indicated that the species was declining, state and federal biologists were stunned when they launched a belated search for the bird in 1994 and "realized the po'ouli wasn't there anymore," says Thane Pratt of the Pacific Island Ecosystems Science Center.
Pratt notes that the Hawaii Department of Land and Natural Resources has fenced most of the Hanawi reserve, a difficult and expensive task, and has removed many of the feral pigs that ravaged the forest understory. But the Interior Department scientist admits that efforts to save the species "should have started 10 years ago. I don't think the po'ouli will make it."
Casey, however, remains optimistic. "The birds still have a chance if we can get the toxicants out there and protect their nests from rats," she says. Adds the Peregrine Fund's William Burnham: "Millions of visitors come to Hawaii and mostly what they see are introduced plants and birds. We've lost more of the nation's biodiversity in Hawaii than in all of the rest of the states." Burham insists that "the po'ouli should not be allowed to just go quietly into oblivion, if we can prevent that end."