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They finally discovered that between 1970 and 2014, the size of vertebrate populations had decreased by 60%. on average. It's absolutely not the same as saying that humans have slaughtered 60% of animals – a distinction that the technical supplement of the report explicitly states. "This is not a census of all wildlife, but the evolution of the size of wildlife populations," write the authors.
To understand the distinction, imagine that you have three populations: 5,000 lions, 500 tigers and 50 bears. Four decades later, there are only 4,500 lions left, 100 tigers and 5 bears (oh my God). These three populations decreased by 10%, 80% and 90% respectively, which means average decline of 60 percent. But the total number of real animals increased from 5,550 to 4,605, which represents a drop of only 17%.
For similar reasons, it is also unfair that we have "killed more than half of the world's wildlife populations" or that we may be blamed for "wiping out 60% of the animal species" or to have 2014. "All these things could be true, but they all make statements on metrics that have not been evaluated in the Living Planet index.
Uncertainties increase when we consider that the 63,000 vertebrate species are Verry much outnumbered by the countless millions of species of invertebrates – creatures without thorns such as insects, worms, jellyfish and sponges, which make up the majority of animal life. Their fate is more obscure because scientists have collectively spent less time monitoring them. They are harder to study and attract less attention than supposedly more charismatic vertebrates – though plans are underway to give them what they deserve.
The average decline of 60% from one population to another also obscures the fate of each species. In the hypothetical scenario above, the lions are still doing well, the tigers have problems and the bears are about to disappear. And among the species in the current Living Planet Index, half of the species are increasing in number, whereas only half are descending. This means that for those who are declining, the outlook is even worse than it seems.
None of this is to let humanity out of trouble. Since prehistoric times, humans have killed so many species of mammals that it would take between 3 and 7 million years of evolution to achieve an equivalent diversity. At least a third of amphibians are at risk of disappearing due to climate change, habitat loss and an apocalyptic killer fungus. Even invertebrates are not unhooked. There may be less data for them, but existing data paint an alarming picture of rapidly disappearing insects, even in forests believed to be intact. Meanwhile, in the oceans, coral reefs are bleaching too quickly to recover, with half of the coral reefs in the Great Barrier Reef having died since 2016. All of this evidence suggests a period of mass extinctions of the past. When reality is so sensational, it is not necessary to sensationalize it further.
