The latest health check has been done on wildlife, and it’s not pretty. A New report Two of the world’s leading environmental groups have revealed that the average size of wildlife populations worldwide has shrunk dramatically, with what the report calls an “alarming” 73 percent over the past 50 years.
The Living Planet Report published by the World Wildlife Fund (WWF) and the Zoological Society of London (ZSL) found that animals living in rivers and lakes, e.g. Amazon river dolphinsThe most serious decline has been experienced. Populations of these freshwater species have declined by an average of 85 percent, according to the Living Planet Index (LPI), a tool for measuring wildlife populations on which the report is based. Across the fauna, meanwhile, wildlife populations are disappearing fastest in Latin America and the Caribbean – a part of the world that’s home to an extraordinary diversity of life. The study did not include invertebrates such as insects and snails.
Losing wild animals is not good for anyone. Bats eat insects and use less pesticides, yet many of them are harmed. Parrotfish, which have declined in some areas, can improve the health of coral reefs that protect coastal communities. All kinds of birds and mammals help pollinate plants and spread seeds throughout the forest, sustaining the forest and rainfall; Many of them are also disappearing.
“It’s not just about wildlife,” Daudi Sumba, WWF International’s chief conservation officer, said in a press call Monday when the report was unveiled. “It’s about the essential ecosystems that sustain human life.”
The new report is an alarming status check on the state of our planet, and the headline numbers it reveals will likely be cited in countless news and government reports. The Living Planet Index is one of the key metrics used to track global progress in environmental conservation efforts.
But… is it right?
It is naturally difficult to come up with simple statistics to describe the state of the world’s wildlife, but more than half a dozen scientists have told me that the methods used to calculate the index may overstate wildlife decline, and perhaps significantly so. Some have even called it confusing. One researcher worries that if leading environmental groups exaggerate the decline of wildlife, it could ultimately undermine public confidence, making action against a real crisis much harder to achieve.
While there is no question of biodiversity loss, growing criticism of the WWF’s estimates cast doubt on the extent of the loss – or at least the ability of science to accurately measure it.
Scientists poke holes in WWF’s original image
Before digging into the report, it’s important to reiterate: biodiversity loss really is a crisis. It is unequivocal. Coral reefs are overheating and dying in large numbers. North America has lost something 3 billion birds. Insects are really disappearing. The extinction rate is accelerated. In Hawaii, which has been called the extinction capital of the world, entire species of birds — and all the cultural heritage they carry — are glowing as I write this.
A new WWF report points to this alarming trend. We are living in a time of profound loss of biodiversity.
It is not easy to calculate a single figure to encompass all these losses. Ecosystems are incredibly complex, and counting animals year after year is difficult and time-consuming. “Making a single estimate for all species in all locations is extremely challenging,” said Laura Melissa Guzmanis a quantitative biologist at the University of Southern California. “I don’t think we’ve reached a consensus as a scientific community on what the best way to do this is.”
WWF’s methodology relies on something called the Living Planet Index, which is produced by ZSL. It measures the average change in animal populations worldwide since 1970. To come up with the global LPI, scientists first calculate how individual populations of birds, mammals, reptiles, amphibians and fish have changed, as I wrote in 2022, when WWF published the previous installment. A population of 1,000 manatees lost 500 decreased by 50 percent. The same is true for the population of 10 which lost only five. Then they average all those changes to create a number, whether they increase or decrease. That means the index is an average of changes in population size, not an average of the number of animals lost.
It’s confusing. In the past, many media stories have misinterpreted statistics from the index and reported that the world has lost more than two-thirds of its wildlife over the past 50 years. it’s wrong The headline number — two-thirds, or in the case of the new report, 73 percent — refers to the average decline in the population of thousands of different animals, not the total number of animals.
But a more fundamental problem than the bad headline is that the index – the basis of the new report – was not calculated correctly, a team of researchers from the Czech Republic’s Center for Theoretical Studies, a joint institution of Charles University and the Czech Academy of Sciences.
Earlier this year, they revealed a paper in the journal Nature communication This indicates that they consider mathematical errors in the LPI. These errors, the authors claim, bias the index and exaggerate wildlife declines.
The study takes issue with a number of issues, including the mathematics used to calculate the index and how ZSL handles low-quality population data. That low-quality data contains population trends — fluctuations in the number of animals — based on counts from just a few points in time. for one Various complicating factorsZSL’s choices in how to calculate the index bias the data toward reduction, the authors say. In reality, decline and growth are more balanced, they say.
One example relates to sampling error, in which scientists do not accurately report the number of animals in a wildlife population, perhaps because they are difficult to identify. If the population is low to begin with, accidentally undercounting animals has a more dramatic, negative effect on population trends than accidentally overcounting.
“I’m really convinced that the decline in vertebrate populations is not as severe as the LPI says,” David Storch, study co-author and researcher at the Center for Theoretical Studies, told Vox.
Several scientists were not involved in it Nature communication The study told Vox that the concerns the article raised are valid and that biases embedded in the calculations may indeed be exaggerating wildlife declines. Rodolfo DirzoA Stanford University biodiversity researcher who reviewed the new report said that while the magnitude of the wildlife population decline is extreme, it is likely smaller than what WWF’s report indicates because of how the LPI was calculated. (Disclosure: Dirzo was one of my advisors in graduate school.)
“Given the widespread adoption of LPIs in the global biodiversity policy arena, the kind of comprehensive sensitivity analysis of LPIs performed by Toszogiova and colleagues is long overdue. Bruce Youngchief scientist at NatureServe, a nonprofit wildlife information organization, said in an email “I was always convinced that the LPI authors presented their results.”
An early version of this though Nature communication While the study was available in 2023, WWF did not change how the LPI is calculated in response to the paper. Storch believes there is an incentive to keep the index as it is. It’s not so much a scientific tool, he says, but a tool to raise awareness — and raise money — about the biodiversity crisis.
“I see these indicators more as a communication tool,” said Rachel Solmann, a quantitative ecologist at the Leibniz Institute for Zoos and Wildlife in Berlin, who was not involved in the new report. Nature communication Study “I wouldn’t put too much faith in its actual numerical value.”
I raised these criticisms with scientists at WWF and ZSL. Robin FreemanA scientist at ZSL who was involved in the LPI analysis said he disagrees that the biases overestimate the extent of wildlife decline. Changing the way the ZSL index is calculated to remove what some researchers see as statistical bias will have its own consequences, he said. Freeman arguing Removing less detailed or more error-prone data from the calculations—most of which are from poorer areas of the tropics where there is less research—may fail to capture the full picture of wildlife decline.
Louse McRae, another ZSL scientist who works on the index, added that it’s also possible that the LPI actually underestimates the scale of the decline. That’s because the index tends to include more population data from birds and mammals, well-studied groups that are generally declining less than reptiles and amphibians, he said.
“We do a lot of work examining datasets, examining the effects of outliers and extreme changes in the population,” Andrew TerryDirector of Conservation and Policy of ZSL, Dr. in a press briefing on Monday. Speaking about the index, he said ZSL is “confident in its robustness.” (ZSL published one Technical documents (along with new reports that detail its testing.)
Amy Falah, a spokeswoman for WWF, said the main objective of the Living Planet Report is to “raise awareness of the scale of the environmental challenges facing our planet and drive urgent action that prioritizes nature in global decision-making.” That’s why the group released it ahead of COP16, a major UN biodiversity conference, where environmental leaders will meet to develop plans for nature conservation.
“LPR’s central mission has always been to inform and influence policy decisions that put nature at the center of solutions to the challenges facing our planet,” Falla said.
We know wildlife is declining. Does it matter if it is exaggerated?
yes and no If leading research and advocacy groups like WWF are seen to be exaggerating the problem, the public may lose a sense of urgency and be less likely to lend support to what is a very real problem.
“There is a real risk of overstating the scale of the biodiversity crisis,” Young of Natureserve told me. “The public may get the impression that the conservation community is prone to exaggeration and therefore calls for action to reduce wildlife damage may be answered.”
Yang also noted that “Extinction Denial“The community — who deny we’re living through a human-driven sixth mass extinction — offers examples, real or not, that show wildlife is doing better than we thought. It captures examples of successful conservation efforts to measure biodiversity loss. Makes it all the more important to do.
Then again, we’re just talking about the shadows of the fall – the biodiversity crisis is really, really bad, or really, really, really No matter how specific the bad LPI is, it illustrates a trend of deep nature damage that no serious scientist disputes. “The report serves to draw attention to the fact that many species of vertebrates have experienced significant population declines,” said Dirzo.
If the image ultimately serves as a communication tool, it is an effective one, judging by how widely LPI is reported and cited. “Our aim is to use it as a tool to raise awareness about the twin crises of nature damage and climate change and to get the public and private sectors to take action,” Falla said.
And to be clear: communication is really important. Wildlife degradation remains a problem to some extent Low public awarenessEven compared to other environmental concerns like climate change. That in itself is alarming, considering the sheer scale of the problem and how it affects us all. We are talking about the ongoing decline of ecosystems with immeasurable spiritual and cultural value that provide human communities with clean water, healthy food and other basic needs. They are immutable.
If WWF’s new report — and the LPI index — can help inform the problem, it looks like it’s finally working.
“It shows us that we are still not doing enough,” said Gerardo CeballosAn Ecologist at the National Autonomous University of Mexico (UNAM). “The most important thing to understand is that we cannot save humanity if we cannot save biodiversity.”
“People have accused me and other people of being alarmists,” Ceballos told me. “We are alarmed because we are alarmed.”
