Rapid advances in genome sequencing have provided promising new techniques to help researchers conserve endangered species, but efforts to resurrect extinct animals raise complex legal, ethical and environmental questions, experts said at a 4 November event at AAAS.
"If you're into watching Star Trek, you might think that this is something coming down the pike in the future, but bringing particular species back from being extinct is a reality now," said Susan M. Haig, a supervisory research wildlife biologist with the U.S. Geological Survey in Corvallis, Oregon. "It's something we will have to deal with [in terms of classifying them], in a legal sense, in a policy sense, and in a moral sense."
Already, scientists have cloned an extinct goat-specifically, a Portuguese subspecies of the Iberian ibex (Capra pyrenaica pyrenaica), said Haig, one of three speakers who joined moderator Richard Harris of National Public Radio to discuss the frontiers of conservation science and policy. The ibex clone, produced after Spanish and French scientists inserted preserved DNA into a modern goat egg and made 57 implantation attempts, died shortly after birth. In Australia, researchers also have so far cloned early embryos of a gastric-brooding frog (Rheobatrachus) that used its stomach as a womb before it went extinct some 30 years ago. Other research teams have announced plans to try and resurrect the passenger pigeon, the woolly mammoth, an extinct type of cattle known as the auroch, and other animals, using a combination of cloning and selective breeding methods.
Such pioneering efforts clearly can help to promote biodiversity, said research zoologist Christopher Meyer, curator of mollusks for the Smithsonian Institution, who also took part in the "Global Challenges" event at AAAS, co-sponsored by Georgetown University Science in the Public Interest and the American Chemical Society.
The accelerating loss of biodiversity has reached a critical threshold: In the United States alone, some 1,566 species are listed by the Fish and Wildlife Service and the National Marine Fisheries Service as being endangered or threatened, said speaker John M. Fitzgerald, an attorney and former policy director for the Society for Conservation Biology. Moreover, he said, some 600 more that occur primarily outside of the United States are also federally listed, which ensures that they receive greater protection by other federal entities such as the Environmental Protection Agency. Many scientists recognize even more species as being endangered, Fitzgerald noted, and a number of species have been identified as eligible for federal listing, yet they are not fully protected by U.S. law because of insufficient resources to do so. The International Union for Conservation of Nature, for example, now includes more than 20,000 species on its "red list."
The approximate number of species considered endangered or threatened in the United States.
John M. Fitzgerald
The approximate number of species on the International Union for Conservation of Nature's global "red list" of threatened species.
Half of all endangered plants and animals "are imperiled because of invasive species," Meyer noted. Habitat loss, hunting, and climate change can also trigger extinctions, which are happening far more frequently than in the past. In response, the Smithsonian's National Museum of Natural History launched a Global Genome Initiative that will cryo-preserve 50% of all families of life on the planet within the next five years, in support of conservation efforts.
Fitzgerald explained that the Endangered Species Act of 1973 has three primary purposes: "The conservation of those species that are threatened with extinction, the conservation of the ecosystems on which they depend, and the implementation of several international conservation agreements and treaties." Administered by the U.S. Fish and Wildlife Service and the Commerce Department's National Marine Fisheries Service, the law seeks to prevent any activities likely to jeopardize listed species or their habitats, and it prohibits the "taking" of endangered species by hunting, commercial trade or any other activity unless permission has been granted in advance by the lead agencies.
Haig said that conservation policymakers often argue against the value of single-species efforts in favor of ecosystem-level conservation, whereas both are important, and ecosystem-level efforts do not take into account the annual cycle needs of migratory species. "I'm frustrated, in a policy sense, when people make this false dichotomy between the importance of single-species recovery efforts and system-level recovery," she said. "We need both for different reasons. Conservationists would make more progress if they would stop arguing this point and focus their efforts on recovery at any level in which they can contribute."
In fact, Fitzgerald noted, the Endangered Species Act promises ecosystem as well as species protection, but common practice may not fully reflect the Act's actual language which provides an ambitious approach that still takes into account economic considerations in different ways, as well as budgetary limits. For example, a 1978 amendment to the law requires that economic impacts must be evaluated before ecosystems can be designated as protected or "critical" habitats for endangered species. Yet another amendment in 1982 made it possible for the government to conclude that protection of a particular candidate species is "warranted but precluded" from listing by higher listing priorities. Earlier this year, for example, the rattlesnake-master borer moth was determined to warrant protection as an endangered or threatened species, but its protection was precluded "due to species with higher priority for listing."
Scientists have announced plans to bring several animals back from extinction, such as the passenger pigeon, woolly mammoth and a type of cattle known as an aurochs. | Flying Puffin, Wikimedia Commons
Conservation research has progressed significantly in recent years, thanks to methods that rely on genomic sequencing, molecular markers, and satellite-based tracking of animals. Molecular markers and banding of the Dunlin (Calidris alpina), a shorebird that migrates from California to Alaska, allowed Haig and colleagues to map the species' precise route. The work illustrated the importance of key habitats, and it also could help provide early warning of bird flu outbreaks. "You can use molecular markers to identify specific populations and their breeding grounds," she explained. "We now have Dunlin markers from all around world … we know when Dunlin are coming through, where and when. If there's a bird flu outbreak in China or someplace in the breeding grounds of Dunlin, and we know they are migrating across Alaska and down the West Coast, we will be able to start catching birds along the route. If they are carrying bird flu, we will know."
Existing technology still limits investigations of species smaller than about 600 grams, Haig pointed out. Current satellite transmitters, which are routinely attached to larger animals to track their migratory patterns, remain too large for small birds, frogs, and other such creatures. Haig said she feels optimistic that this technical hurdle will soon be overcome, though. Meyer said, meanwhile, that the field of conservation science could benefit from enhanced standards for genetic sampling within ecosystems. Fitzgerald said that conservation policy works reasonably well, from his perspective, but ideally, it should take more of a precautionary approach. In the absence of scientific certainty, Fitzgerald explained, the "precautionary principle" would require policymakers to err on the side of caution.