Scientists have been urging conservation NGOs to make decisions based on scientific evidence.However, the big conservation NGOs run into many problems in trying to use the available science. Doing impact evaluations of their own projects is also hard and expensive, sources from the big conservation NGOs say.For their work to be effective, the conservation community needs to develop a common understanding of what credible evidence means, how to best use different strands of evidence, and how organizations can evaluate their work and create evidence that others can use, experts across the conservation spectrum seem to agree.This story is part of a special Mongabay series on “Conservation Effectiveness.” When a female Indian rhinoceros (Rhinoceros unicornis), and then her daughter, died in India’s Burachapori Wildlife Sanctuary last year, conservationists were worried. The rhinos’ horns were intact, so they had not fallen prey to poachers. Their deaths were instead attributed to some “natural cause” that no one could pinpoint. The pair had been introduced to Burachapori, in the northeastern state of Assam, as part of an ambitious and expensive scheme called Indian Rhino Vision 2020 (IRV 2020). The plan aimed to increase rhino numbers in Assam and rewild protected areas like Burachapori and Manas National Park that once held their own rhino populations. For the first few years, it looked like IRV 2020 was working: introduced rhinos adapted well in their new homes, and some even mothered calves. But then, poachers killed 10 of the rhinos in Manas between 2011 and 2016. And about 260 kilometers away, in Burachapori, the newly introduced mother and calf succumbed to that mysterious, fatal natural cause. IRV 2020 is a collaboration between the Assam Forest Department and various conservation groups, such as WWF-India, the International Rhino Foundation, and the U.S. Fish and Wildlife Service. It took several years of planning and preparation. But with armed poachers and puzzling ailments looming in the background, the team decided to reassess the situation and put further translocations on hold. Poaching is a known threat. But fundamental knowledge about what factors affect the health of Indian rhinos in the wild is still lacking, Amit Sharma, WWF-India’s senior coordinator for rhino conservation, told Mongabay earlier this year. Conservation groups frequently work amid that kind of uncertainty in complex, ever-changing environments. So how do they determine which strategy will help a species the most? Is rewilding parks with an endangered species really good for the animal’s future? Is the money better spent working with the nearby communities to reduce poaching pressure on the few existing populations? Is it okay to take on an experimental rewilding project without having gained some fundamental knowledge about the biology of the species? There are no simple answers, of course. Conservation is about making hard decisions. Four of the world’s largest conservation groups that dominate today’s wildlife conservation landscape — the Switzerland-based World Wide Fund for Nature (WWF), and U.S.-based Conservation International (CI), the Nature Conservancy (TNC), and the Wildlife Conservation Society (WCS) — make these decisions constantly. These big conservation NGOs (BINGOs) employ thousands of people and spend millions of dollars spearheading projects on nearly every continent, from humid tropical rainforests to the ocean’s mysterious depths. In doing so, they often determine whether a species can avoid extinction. But how do the groups know what works? Indian rhinoceros in Assam, India. Photo by Anuwar Ali Hazarika via Wikimedia Commons (CC BY-SA 4.0). How to save a species? For a long time, the conservation community has leaned on intuition, personal experiences, ideology, or random trial and error to decide on a conservation strategy. Sometimes, conservation groups are simply opportunistic, banking on the strategy that attracts the most funding or political support. But over the last few decades, scientists have been pushing for more evidence-based conservation. They have been urging conservation NGOs to use the best available science to prescribe strategies. Just as you would assume the treatment or drugs your doctor recommends are backed by evidence from medical research, so should the plans prescribed for saving species from extinction be supported by the best available evidence, scientists say. By scientific evidence, many researchers refer to peer-reviewed studies, which can take many forms. Studies can record how certain environmental outcomes have changed in a place since the implementation of a strategy, like, say, changes in tiger numbers since the creation of a protected area. Studies might use high-tech analyses of satellite images to measure changes in deforestation levels or record people’s personal experiences and perceptions to describe how a strategy affects communities or wildlife. Then there are systematic reviews that look at multiple studies that have asked similar questions, such as “Does trophy hunting help save African elephants?” These reviews then compare those individual studies’ results to discern patterns or trends. Like all fields of science, the quality of conservation effectiveness research varies a lot. The gold standard is completely experimental randomized control trials or quasi-experimental controlled studies (non-randomized experiments) that can definitively attribute the observed changes to the strategy and not to some other factor. Such studies might compare, for instance, a block of protected forest with a control site: another block of forest that is not legally protected, but is otherwise nearly identical to the protected forest. Overall, there has been a rise in peer-reviewed studies looking into the effectiveness of conservation strategies, experts say. But NGOs don’t seem to be using them, William Sutherland and Claire Wordley of the Conservation Evidence Project at the University of Cambridge, U.K., wrote in an article recently. They called it “evidence complacency:” the persistence of a culture in which conservation practitioners neither use available scientific evidence to make decisions nor measure the outcomes of their actions. This complacency is leading to a waste of money, time, and opportunities, the researchers wrote. And they worry that it could show conservation as “an unjustifiable investment.” Sources from the four BINGOs agreed that scientific evidence should be a key component of decision-making. They also said that there is a growing demand for evidence-based conservation not just from academic scholars, but from within the NGOs themselves. “I think practitioners are generally keen to use and gather evidence,” Edward Game, the lead scientist for TNC’s Asia Pacific region, told Mongabay. In fact, all four groups have either established new programs or updated existing ones to specifically look at generating and integrating evidence into their conservation decisions. TNC, for instance, upgraded their existing framework, “Conservation by Design,” to “Conservation by Design 2.0 (CbD 2.0)” in 2015. One of CbD 2.0’s major updates is to “robustly draw upon and build the evidence base for conservation.” In 2014, WCS launched the “5 Measures Program” to better track the effectiveness of its projects. WWF has also been building up its global science team, and, through its conservation impact initiative, moving toward a more evidence-based approach to tracking its projects over time. Similarly, CI has been working toward incorporating more evidence and monitoring into its programs. All of this sounds encouraging. “But the use of evidence in conservation decision-making is neither as effective nor rigorous as it could be,” Game said. Part of the problem, the sources at the BINGOs said, is that the kind of peer-reviewed studies the “evidence complacency” article’s authors and other researchers are urging conservation practitioners to pay more heed to offer only a narrow view of the evidence.