Wildlife populations have plummeted 68% in less than half a century and the "catastrophic" decline shows no sign of slowing down, a major conservation report published Wednesday warns.

Driving the news: The "Living Planet Report 2020" from the World Wildlife Fund for Nature (WWF) that monitored 4,392 species of mammals, birds, fish, reptiles and amphibians from 1970 to 2016 points to one underlying cause for the populations decline and deterioration of nature: humanity.

What they found: Deforestation undertaken to increase agricultural land space was the biggest contributor to the decline, according to the collaborative biennial report from the WWF International and the Zoological Society of London.

• Three quarters of all freshwater and a third of all land mass is dedicated to food production, the report notes.
• Populations in Latin America and the Caribbean have seen the biggest fall, with an average decline of 94%. Global freshwater species have fallen 84% on average.
• "Nowhere in the ocean is entirely unaffected by humans," notes the report, with overfishing and pollution exacerbated by climate change cited as major problems.

Of note: The findings concur with those of a 2019 United Nations report warning that 1 million animal and plant species are under threat from extinction — driven by changes in land and sea use; "direct exploitation of organisms," such as hunting, fishing and logging; climate change; pollution; and invasive species.

What they're saying: WWF-US President and CEO Carter Roberts said in a statement, "As humanity’s footprint expands into once-wild places, we're devastating species populations. But we're also exacerbating climate change and increasing the risk of zoonotic diseases like COVID-19."

Between the lines: The spillover of pathogens from animals to humans — driven mainly by human behaviors like urbanization and the demand to eat meat — is increasing, Axios' Eileen Drage O'Reilly notes.

• These Zoonotic diseases have "quadrupled in the last 50 years, mostly in tropical regions," according to a letter from more than 100 wildlife and environmental groups sent to Congress in March.

The bottom line: A study published in the journal Nature Thursday and co-authored by over 40 nonprofits and academics finds cutting food waste and opting for more nutritional diets would help prevent further losses to the ecosystem.

• The WWF report also finds that the environmental crisis can be mitigated if world leaders and others take urgent action on consumption industries, including ending deforestation.

Read the full "Living Planet Report 2020," via DocumentCloud:

Go deeper: Coronavirus is tied to climate and biodiversity crises