Study reveals how species once extinct in the wild have bounced back
Banner image of a red-billed curassow (Crax blumenbachii)
- Researchers studying the impact of conservation actions since the landmark 1992 Rio Earth Summit say that at least 21 species of birds and seven mammals have been saved from extinction through direct human intervention.
- In Brazil, these include five species of endemic birds, among them the Alagoas curassow (Pauxi mitu), the Lear’s macaw (Anodorhynchus leari) and the Spix’s macaw (Cyanopsitta spixii), all of which were at one point extinct in the wild.
- While some species have returned to nature, others have gone extinct during the last two decades, despite conservationists’ best efforts.
- The study identifies control of invasive species, protection of natural areas, and ex-situ (or off-site) conservation, including captive-breeding programs, as among the most effective interventions in preventing species extinctions.
In 1992, global leaders gathered at a United Nations summit in Rio de Janeiro to sign the landmark Convention on Biological Diversity (CBD) to promote sustainable development. Eighteen years later, at a summit in Aichi, Japan, representatives of 193 countries followed up on the CBD with a 20-goal commitment to reduce global pressures on the natural world by the end of 2020.
Number 12 on this list of Aichi Biodiversity Targets calls for preventing the extinction of endangered species, particularly those with declining populations, and improving their conservation status.
To understand whether this commitment has been achieved as the time for the Aichi Biodiversity Targets expired, and to what extent, an international team led by scientists at Newcastle University in the U.K. conducted a survey to find out how many bird and mammal species have been saved from extinction thanks to conservation efforts.
“We wanted to identify how many extinctions have been avoided since 1993, when the Convention on Biological Diversity came into force, and since 2010, when the latest targets relating to it were adopted, including that on prevention of extinctions,” said Rike Bolam, lead author of the study published in the journal Conservation Letters. “Our goal was to know how the policy has impacted these numbers.”
The study focused only on birds and mammals because they’re the most studied groups of animals, with the largest amount of global data available. Only species with an IUCN Red List conservation status of “extinct in the wild,” “critically endangered” or “endangered” at any point since 1993 were analyzed.
After an extensive survey, the researchers determined that conservation actions have prevented 21 to 32 extinctions of birds and seven to 16 extinctions of mammals since 1993; and nine to 18 bird extinctions and two to seven mammal extinctions since 2010.
At the same time, 10 species of birds and five species of mammals have gone extinct in the past 17 years (or at least they are strongly suspected to have died out), despite conservation efforts by governments and nongovernmental organizations.
However, the researchers note that if nothing had been done, these extinction rates could have been between 2.9 and 4.2 times higher.
“It is encouraging that some of the species we have studied have recovered very well,” Bolam said. “Our analysis, therefore, provides a positive message that conservation has substantially reduced the extinction rates of birds and mammals. Although extinctions have also occurred in the same period of time, our work shows that it is possible to prevent them.”
Those we lost and those we saved
Among the mammal species suspected to have been extinct in the wild since 1993 are a Papua New Guinea marsupial, a freshwater dolphin from China, and a monkey from Africa. The bat Pipistrellus murrayi and the small rodent Melomys rubicola, both from Australia, are confirmed to be extinct — a process that can take several years to conclude definitively.
“All the species of birds that disappeared lived on islands like the Galápagos or Hawaii, or in Central or South America,” Bolam said. “For island birds, the main threats were invasive species in combination with habitat loss. For Central or South America it was mainly habitat loss, often in addition to hunting.”
The good news is that species like the Iberian lynx (Lynx pardinus), the California condor (Gymnogyps californianus), the pygmy hog (Porcula salvania), native to India, Przewalski’s horse (Equus ferus przewalskii) of the Mongolian steppes, and the Puerto Rican parrot (Amazona vittata), among others, saw an increase in their populations, thanks to conservation efforts.
Conservation actions with better results
Besides studying which animals have been saved from extinction in recent decades, the researchers also evaluated which preservation strategies have been the most successful. According to Bolam, among the most effective are control of invasive species, protection of natural areas, and ex-situ (or off-site) conservation, including captive-breeding programs.
Twenty of the bird species studied were found to have benefited from work done in zoos and wildlife refuges. The wild population of the Puerto Rican parrot, for instance, hit a low of just 13 individuals in 1975. But thanks to an intensive captive-breeding program, and a reintroduction process that began in 2006 at Río Abajo State Park, the bird has bounced back, and today numbers between 80 and 100 individuals at two sites.
Breeding of captive animals also helped bring Przewalski’s horse back from the bring after the wild population went extinct in the 1960s. Today, there are approximately 400 of the horses roaming free in their original habitat.
Bolam said one of the goals of the global study is to serve as an important scientific source for new conservation policies. “We need to avoid the underlying causes that are leading to the extinction of species, such as habitat loss through agricultural expansion. There are models that suggest that we can achieve this while ensuring food security, for example, by minimizing food waste,” she said. “Another key point is the conservation actions aimed at the most threatened species, such as those of our study, the ones that are very close to extinction.”
Success stories from Brazil
The 32 bird species that the study said had likely been saved from extinction are endemic to 25 countries, including six from New Zealand, five from Brazil and three from Mexico. Of the top 10 countries with the greatest number of bird species, six are in South America: Colombia, Peru and Brazil are the top three on the list.
In the case of Brazil, NGOs, government agencies and private breeders have worked in partnership in recent decades to preserve the diversity and survival of many native bird species. Those that the study identified as having been successfully saved from extinction are the Alagoas antwren (Myrmotherula snowi), the Alagoas curassow (Pauxi mitu), the red-billed curassow (Crax blumenbachii), the Lear’s macaw (Anodorhynchus leari) and the Spix’s macaw (Cyanopsitta spixii).
A mascot of the Caatinga dry forest in Brazil’s northeast, the Spix’s macaw hasn’t been seen in the wild in two dacades. But a reintroduction program — involving international breeders and a lot of controversy — led to the return last March of 52 of the birds. They are now undergoing a process of acclimatization and adaptation ahead of their expected release into a protected reserve in the municipality of Curaçá later this year.
Extinct in the wild since the 1980s, the Alagoas curassow has already returned to some areas of Brazil’s Atlantic Forest. That success story started in 1979, when breeder Pedro Nardelli rescued five curassows from an area about to be deforested. Over the following years, he helped develop a network that included experts and institutions from across Brazil — including the Museum of Zoology of the University of São Paulo and CRAX (the Society for Wildlife Research) — who together worked to increase the bird’s captive population while maintaining a diverse gene pool.
“The genetic work carried out was very important,” said Mercival Roberto Francisco, a biologist at the Federal University of São Carlos, one of the institutions involved in the reintroduction program. “It focused on counseling for the best matings, in order to preserve as much as possible of the genetic variability along the generations and increase the levels of heterozygosis of the squad.”
At the end of 2019 — 40 years after the rescue of those five initial Alagoas currasows — three mating pairs were released in Mata do Cedro Private Natural Heritage Reserve (RPPN), in the municipality of Rio Largo in Alagoas state.
The work is still far from over, said Roberto Azeredo, a breeder with CRAX who inherited part of Nardelli’s flock 20 years ago. “The birds will be permanently monitored by radio transmitters. We need to follow up on the main information about the biology of the species and also avoid hunting and/or capture,” he said.
Ensuring the security of the release area is one of the major challenges when reintroducing any animal into the wild. “Hunting is still a very common practice in several parts of Brazil, and in the state of Alagoas this is no different,” Francisco said.
If all goes well, the plan is to reintroduce three more mating pairs each year until 2024. “Due to the fact that there are no more continuous areas of Atlantic Forest in the northeast of Brazil, some populations might be formed in different fragments of forest,” Francisco said. “Although at the moment it is still difficult to predict anything, we believe that a number of 30 reproductive couples per area would be a safe number.”
CRAX is also responsible for the progress made with another curassow, the red-billed one. This beautiful bird, with its black body, imposing crest and flashy beak, was similarly almost exterminated. Over the last 40 years, Azeredo’s team has managed to breed hundreds of individuals in captivity and release about 400 into the wild.
Bolam, F. C., Mair, L., Angelico, M., Brooks, T. M., Burgman, M., Hermes, C., … Butchart, S. H. (2020). How many bird and mammal extinctions has recent conservation action prevented? Conservation Letters, e12762. doi:10.1111/conl.12762