December 6, 2022

The Living Planet Index for 2022 is out. Here's how to make sense of it.

The Living Planet Index for 2022 is out. Here’s how to make sense of it.

It is clear that wildlife suffers greatly on our planet, but scientists do not know exactly how much. It is very difficult to determine a comprehensive number. Counting wild animals – on land and at sea, from mosquitoes to whales – is no small feat. Most countries lack national monitoring systems.

One of the most ambitious efforts to fill this void is published every two years. known as Living Planet IndexIt is a collaboration between two major conservation organizations, the World Wide Fund for Nature and the Zoological Society of London. But the report has repeatedly led to inaccurate headlines when journalists have misinterpreted or overestimated its findings.

The assessment’s latest figure, released Wednesday by 89 authors from around the world, is the most worrisome yet: From 1970 to 2018, the observed vertebrate population declined by an average of 69 percent. That’s more than two-thirds in just 48 years. It’s a staggering number with serious ramifications, especially as countries prepare to meet in Montreal in December to try to agree on a new global plan to protect biodiversity. But does that mean what you think?

Remember that this figure relates only to vertebrates: mammals, birds, reptiles, amphibians and fish. Absent are creatures without spines, although they make up the vast majority of animal species (scientists have less data about them).

So, have land vertebrates declined 69% since 1970?


The study tracks selected groups of 5,320 species, and all existing relevant published research disappears, adding more each year when new data allows. They include, for example, a group of whale sharks in the Gulf of Mexico counted from small planes flying low over the water, and birds that were counted by the number of nests on the cliffs. Depending on the species, tools such as camera traps and clues such as trail droppings help scientists estimate the population in a particular location.

This year’s update includes approximately 32,000 of this population.

There is a temptation to believe that an average decline of 69 percent in this population means that this is the share of monitored wildlife that has been eliminated. But this is not true. An addendum to the report provides an example of why.

Imagine, as the authors wrote, that we start with three groups: birds, bears, and sharks. The bird population is down to 5 from 25, which is an 80 percent drop. Bears drop to 45 animals from 50, or 10 percent. And sharks drop to 8 from 20, or 60 percent.

This gives us an average drop of 50 percent. But the total number of animals fell to 92 from 150, down about 39 percent.

The indicator is designed in this way because it seeks to understand how the population has changed over time. It does not measure the number of individuals present.

“The Living Planet Index is truly a contemporary view on population health that underpins the work of nature across the planet,” said Rebecca Shaw, chief scientist at the WWF and author of the report.

Another important factor is the way the controlled population ends up in the index. They do not represent a large random sample. Instead, they reflect the available data. So there is a very potential bias in determining which species is being tracked.

One argument over whether a small number of the population is in a state of drastic decline has called into question the overall results. Two years ago, a study in Nature found that only 3 percent of the population were driving a sharp decline. When they were removed, the global trend turned to increase.

The paper sparked a flurry of responses in Nature as well as an additional explanation and stress test for this year’s update. On the bright side, the authors note that about half of the population in the Living Planet Index is stable or increasing. However, when they tried to exclude the population with the most drastic changes in both directions, down and up, the average proportions remained steep.

“Even after removing 10 per cent from the full data set, we still see a 65 per cent drop,” said Robin Freeman, head of the Indicators and Assessments unit at the Zoological Society of London and author of the report.

yes. Some scientists believe the report actually downplays the global biodiversity crisis, in part because it is devastating decrease in amphibians It may be underrepresented in the data.

Over time, the trend does not change.

“Year after year, we cannot begin to improve the situation, despite major policies,” said Henrique M. Pereira, professor of conservation biology at the German Center for Integrative Biodiversity Research who was not involved in this year’s report. “At most we were able to slow the decline somewhat.”

Latin America and the Caribbean experienced the worst regional decline, down 94 percent from 1970. This pattern was most pronounced in freshwater fish, reptiles, and amphibians. Africa came in second with 66%. The Asia Pacific region saw 55 per cent. The region defined as Europe and Central Asia saw a smaller decline of 18 percent, as did North America of 20 percent. Scientists have confirmed that the most severe biodiversity losses in these two regions likely occurred well before 1970 and are not reflected in these data.

Scientists know the cause of biodiversity loss. On Earth, the main driver is agriculture, with people turning forests and other ecosystems into farmland for livestock or oil palm. At sea, it’s fishing. There are ways to do both more sustainably.

If climate change is not limited to 2 degrees Celsius, preferably 1.5 degrees, its consequences are expected to become the main cause of biodiversity loss in the coming decades, the report said.

In December, the nations of the world will come together to try to reach a new agreement to protect the planet’s biodiversity. the last one It often failed to achieve its goals. Dr. Shaw said the Living Planet Report provides evidence of how successful this time around. The important lesson is that conservation does not work without the support of local communities.

“When we get really focused conservation efforts that involve the community, that get the communities to manage the outcomes because they benefit from them, we see that it’s possible to increase the population,” she said. “That really bright spot.”