Global animal populations are declining, and we've got limited time to try to fix it.

That's the upshot of a new report from the World Wildlife Fund and the Zoological Society of London, which analyzed years of data on thousands of wildlife populations across the world and found a downward trend in the Earth's biodiversity.

According to the Living Planet Index, a metric that's been in existence for five decades, animal populations across the world shrunk by an average of 69% between 1970 and 2018.

Not all animal populations dwindled, and some parts of the world saw more drastic changes than others. But experts say the steep loss of biodiversity is a stark and worrying sign of what's to come for the natural world.

"The message is clear and the lights are flashing red," said WWF International Director General Marco Lambertini.

According to the report's authors, the main cause of biodiversity loss is land-use changes driven by human activity, such as infrastructure development, energy production and deforestation.

Climate change may become the leading cause of biodiversity loss

But the report suggests that climate change — which is already unleashing wide-ranging effects on plant and animal species globally — could become the leading cause of biodiversity loss if rising temperatures aren't limited to 1.5°C.

Lambertini said the intertwined crises of biodiversity loss and climate change are already responsible for a raft of problems for humans, including death and displacement from extreme weather, a lack of access to food and water and a spike in the spread of zoonotic diseases.

He said world leaders gathering at the U.N. Biodiversity Conference in Montreal in December should take major steps to reverse environmental damage.

"This is the last chance we will get. By the end of this decade we will know whether this plan was enough or not; the fight for people and nature will have been won or lost," Lambertini said. "The signs are not good. Discussions so far are locked in old-world thinking and entrenched positions, with no sign of the bold action needed to achieve a nature-positive future."

But the dire news comes with signs of hope: Though there is no panacea, experts say there are feasible solutions to the loss of biodiversity.

Solutions range from the conservation of mangroves to a cross-border barter system in Africa to the removal of migration barriers for freshwater fish, the report said.

Human habits have to change

WWF chief scientist Rebecca Shaw told NPR that humans have the opportunity to change how they do things to benefit nature.

"We don't have to continue the patterns of development the way we have now. Food production, unsustainable diets and food waste are really driving that habitat destruction. And we have an opportunity to change the way we produce, the — what we eat and how we consume food and what we waste when we consume our food," Shaw said. "Little things that we can do every day can change the direction of these population declines."

The report calculated the average change in the "relative abundance" of 31,821 wildlife populations representing 5,230 species.

Latin America and the Caribbean saw a whopping 94% average population loss and Africa saw a 66% decline, while North America experienced only a 20% drop and Europe and central Asia saw its wildlife populations diminish by 18%.

The WWF said the disparity could be due to the fact that much of the development in North America and Europe occurred before 1970, when the data on biodiversity loss started.