WWF says conservation alone cannot reverse the decline but there must be efforts to tackle the causes.
The biggest pressures come from farming, which can destroy the habitats wildlife depends on, and burning fossil fuels for energy, which drives climate change.
The organisation says the money is flowing the wrong way. In 2023, about $7.3 trillion (£5.53tn) went into activities that harm nature, compared with $220bn spent protecting or restoring it, the report estimates – a ratio of roughly 33 to one.
Barrett has worked on seven Living Planet reports, but he said this was the first where the takeaway message was to focus on hope.
“The fact that the science is still telling us that we’ve got a way out is actually extraordinary,” he said.
“So it’s a closing window of opportunity, but it’s still open, just, if we act now.”
Additional reporting Kevin Church and Miho Tanaka