Decline in wildlife could be less catastrophic than expected

A hummingbird in Colombia (illustrative image).

-

In September, WWF concluded that the world had lost 68% of its vertebrates in almost 50 years.

But this catastrophic figure of global animal populations would be overestimated, according to a study published Wednesday by the journal

.

At the origin of this possible error, the statistical methods used to reach these conclusions.

The previous WWF report from 2018 described a decline of about 60% in these populations of mammals, birds, fish, reptiles and amphibians between 1970 and 2014. The organization used the Living Planet index produced every two years by the Zoological Society of London (ZSL).

It is the latter that is evaluated by the study of

, which considers it inflated.

Catastrophic figures that lead to inaction

Examining 14,000 vertebrate populations monitored since 1970, the study's authors conclude that 1% are in extreme decline and that if we remove them from the equation, all remaining populations show no increasing trend. or down.

“Taking extreme groups into account fundamentally alters the interpretation of general vertebrate evolution,” they say, noting that this “omnipresent catastrophe” message can lead to “desperation, denial and inaction”.

They therefore suggest using more localized assessments “to help prioritize conservation efforts”.

"Putting all the population curves together in a single digit can give the impression that everything is declining everywhere, based on math rather than reality," senior author Brian Leung of the university told AFP. McGill in Montreal.

“A more nuanced picture is more precise: there are centers of population in extreme decline, in ecosystems which, apart from that, are neither improving nor declining.

However, there are also a few geographic areas where most of the populations examined appear to be declining.

It is important to identify these, ”he continues.

Like birds in Asia-Pacific or tropical reptiles.

An alarming UN report

The fact that the Living Planet index is "sensitive" to extreme variations in population "is not a revelation", tempered in a blog Dr. Robin Freeman, of the ZSL, co-author of the study but also a member. of the team developing the Living Planet index.

But such composite indices "can serve as a barometer for the health of ecosystems", like stock indices, he argued.

Asked by AFP, WWF referred to its partner ZSL.

Studies alarming a large-scale destruction of biodiversity by human activities have multiplied in recent years.

In an unprecedented report, the UN Group of Experts on Biodiversity (IPBES) in 2019 described ecosystems in tatters and estimated the number of species threatened with extinction at one million.

"We are not saying that there are no problems with biodiversity, only that it is not in decline everywhere," insists Brian Leung.

But don't these conclusions risk being seen as an encouragement to do nothing to protect nature?

“It is our concern (…).

But our primary motivation is for science to be correct.

In the long term, the legitimacy of our field depends on it ”, explains the researcher.

Planet

Burma: Discovery of a new species of monkey called Popa langur

Planet

Brittany: Why the basking shark is so popular in the waters of Finistère

• Planet

• Animals

• Biodiversity

• Wildlife

• Nature

• Wwf