Rarity, Darwin wrote in The Origin of Species, precedes extinction. “To admit that species generally become rare before they become extinct,” he wrote, “… is much the same as to admit that sickness in the individual is the forerunner of death.” 

Darwin’s statement was aimed at his fellow naturalists, who still argued over why species went extinct. In the mid 19th century, some scientists believed that Earth had experienced a series of sudden upheavals, in which thriving species suddenly disappeared and new species appeared. To them, extinction was unpredictable. Darwin thought otherwise. The species that were most likely to go extinct were those that were rare, and growing rarer.  

Many modern conservation efforts are organized around this simple truth. The International Union for Conservation of Nature (IUCN), for instance, maintains a Red List of Threatened Species, in which some 116,000 species are assigned a rank, from “least concern” to “critically endangered.” While this system of triage is useful, some conservation biologists argue that it misses important subtleties—and possibilities. Now, the union is working on creating a new, more aspirational framework. “We’ve been thinking of success in terms of what we want to avoid instead of what we want to achieve,” says Molly Grace, a conservation biologist at the University of Oxford and the coordinator of the IUCN task force leading the effort. That is, there is more to conservation than simply preventing extinction.  

The IUCN created its Red List in 1964. Scientists knew the system had shortcomings from the beginning, says ecologist Resit Akcakaya. Two species might both be ranked as “critically endangered,” for example, but one has high prospects of recovery while the other doesn’t. The Red List’s ranking system also misses species that need conservation work but are not in immediate danger of extinction. One example is the American bison, vanished from the vast majority of its former range but unlikely to go extinct. “You can’t say there’s no conservation concern,” Akcakaya says. “It’s just that the concern isn’t about the risk of extinction of the species.”  

The Red List’s most glaring omission is its inability to register the effects of conservation efforts. Some species have been listed as critically endangered for decades, Akcakaya says, but this doesn’t necessarily signal failure. In some cases, conservation efforts may have kept the species from going extinct. In others, a species might no longer be endangered but is still dependent on conservation efforts. The ranking system can even create perverse incentives to not downgrade a species from, say, critically endangered to endangered, as their condition improves, he says. Downgrading can mean less attention and funding for a species. “When a species becomes down-listed from endangered to vulnerable, people get upset,” Akcakaya says. 

At a general assembly of the IUCN in 2012, its members resolved to fix some of these problems by creating a Green List of Species—a new roster of species that would quantify the past, present, and future impacts of conservation efforts. This new list wouldn’t replace the Red List but rather augment it. In 2018, a team led by Akcakaya published a paper announcing the draft framework, what they now call Green Status of Species (a change made to avoid giving the impression that the species in question are no longer in need of human help). 

The new framework begins with a definition: “We consider a species fully recovered if it is viable and ecologically functional in every part of its indigenous and projected range.” The first piece, viability, means that the species is no longer in danger of extinction. In the Red List’s terms, it is of least concern. The second piece, function, means that it is performing a role in the ecosystems where it occurs. This is a bit amorphous, Akcakaya admits—with many species, we don’t know exactly what they do—but quantifiable measures like population density can serve as proxies for function. Is the species far rarer than it used to be? Is it common enough to do something? The third part of the definition is that a fully recovered species occupies its whole historical range. While humans have been reshaping habitats in some parts of the world at least since the dawn of agriculture, the Green Status definition places the earliest baseline date at 1500, and the latest at 1950. For most species, scientists will compare their current range with their range in 1750, at the beginning of the Industrial Revolution. 

To assess the Green Status of a species, researchers then compare its condition against the fully recovered ideal, both in reality and in a range of hypothetical scenarios. What is the species’ situation today? What would its situation be today without conservation actions of the past? How will things be in the future with planned conservation? Without that conservation? What is the long-term potential of recovery for the species? 

Biologists then calculate four scores: conservation legacy, conservation dependence, conservation gain, and recovery potential. The first three scores can help researchers assess the effects of conservation efforts in the past, present, and future. The fourth score, recovery potential, can help them assess which species humans are most likely to be able to help. “It hurts a bit, but sometimes you have to make a decision,” says Claudia Hermes. “Is it worth it to make a try, or will it be lost anyway?” 

Hermes is one of the more than 200 scientists who tested the new Green Status framework on roughly 180 species. She is a Red List researcher at the nonprofit BirdLife International and often conducts IUCN Red List assessments. She says that making Green Status assessments was different and challenging. “For Red Listing, you rely very much on solid data, published values, population size, population trends,” she says. The Green Status requires more information about actual and planned conservation and requires the assessor to make judgments about what effects those actions have had and will have. “There’s a lot of educated guesses,” she says.  

“It’s a bit subjective, at least more than the Red List,” says Pablo Acebes, an ecologist at the Universidad Autónoma de Madrid who made Green Status assessments of the guanaco and vicuña, South American wild animals related to the domesticated llama and alpaca. “You don’t have to gather that much information, but you have to think and reflect a lot, and the results can change a lot depending on what you decided.”  

Other scientists have pointed to small problems in the Green Status draft framework. Yvette Harvey-Brown, a conservation officer at Botanic Gardens Conservation International, made Green Status assessments of several tree species. Some tree species have life spans that stretch across human generations, making it difficult to see what effect conservation is having under short time frames. “Compared to insects and animals, it takes longer to have those good news stories,” she says. Similarly, Angela Tringali, an ecologist who assessed the Florida scrub jay, pointed out that the framework doesn’t account for extinction debt—a situation in which actions that will cause a future population decline have already occurred. Florida scrub jays, for example, are long-lived and fiercely territorial, she says. “If a little patch of habitat becomes surrounded by housing developments, the individuals that live there will continue living there.” But after they die, the population will go locally extinct.

Molly Grace says that the task force has incorporated the suggestions made by the scientists who tested the framework. The group is currently taking comments from the IUCN’s 1,300 member organizations and aims to present the final document at the World Conservation Congress, scheduled to take place in June in France (though the conference may be postponed due to the coronavirus crisis). Barney Long, co-chair of the Green Status task force, says that he hopes that the IUCN will formally adopt the framework sometime in 2021.   

Despite their critiques, the scientists who have tested the framework call it a valuable exercise. “I think it’s quite useful,” Hermes says. One of the species whose Green Status she assessed was the California condor. Once, the species ranged across much of North America, but by the 1750s, it lived only in the West, from Baja California north to Vancouver. During the 20th century, the birds suffered the effects of lead and DDT poisoning, poaching, and habitat loss. In 1987, the condor became extinct in the wild. Scientists raised the birds in captivity and began releasing them in 1991.   

Using historical records, Hermes broke the California condor’s range into four spatial units: California, Utah and Arizona, Mexico, and the Pacific Northwest. In each of these subsections, she calculated what full recovery would look like, then compared the bird’s present and future prospects in those regions with that ideal. While the condor still has a Red List status of critically endangered, Hermes says the picture offered by the Green Status assessment is more positive. The birds are highly dependent on ongoing conservation, and recovery will be slow, but in three of the four conservation units, under the best-case scenario, they could be fully recovered in the next hundred years. “It’s actually not looking too bad,” she says. “It’s looking quite good.”