A recent warning to humanity endorsed by thousands of scientists around the world includes "scaremongering" and "overheated" claims while ignoring much of the progress made in recent decades, some experts say.

"It concerns me that the message from science is this doom-and-gloom scenario that just turns off about 75 per cent of people," said Erle Ellis, an associate professor of geography and environmental systems at the University of Maryland, Baltimore County.

There's a small percentage that loves the crisis narrative, and they just repeat it over and over to each other. - Erle Ellis, University of Maryland

"There's a small percentage that loves the crisis narrative, and they just repeat it over and over to each other."​

Ellis, who is also a senior fellow at the California-based think-tank the Breakthrough Institute, said he's "somewhat embarrassed" for his scientific colleagues who have rallied behind this warning, arguing that it mostly talks about negative trends and ignores the increasing wealth, health and well-being of human populations globally.

'A real disservice'

Ted Nordhaus, environmental policy expert and co-chair of the Breakthrough Institute, said while there are certainly global environmental issues that need to be addressed, some of the more "dystopian" forecasts often end up being "wildly inaccurate."

"I think these really overheated claims do a real disservice," he said.

The dire warning, which comes 25 years after a similar missive was issued by scientists, was published in the scientific journal BioScience. Headlined "World Scientists' Warning to Humanity: A Second Notice," the article was signed by more than 15,000 scientists from 184 countries.

It paints a bleak picture of the world's current situation when it comes to freshwater availability, marine life depletion, ocean dead zones, forest loss, biodiversity destruction, climate change and continued human population growth.

"Humanity has failed to make sufficient progress in generally solving these foreseen environmental challenges — and, alarmingly, most of them are getting far worse," it states.

"Soon it will be too late to shift course away from our failing trajectory, and time is running out."

Predictions failed to materialize

When it comes to the issue of overpopulation, the article warns that humanity is putting the world at jeopardy with "our intense but geographically and demographically uneven material consumption" and by failing to recognize rapid population growth as "a primary driver behind many ecological and even societal threats."

Such predictions have been made for centuries, dating back to Robert Malthus who wrote in the 18th century about how population trends would have significant consequences on resources.

Biologist Paul Ehrlich caused waves in 1968 with the publication of The Population Bomb, which predicted that ​overpopulation would result in the starvation deaths of hundreds of millions of people. (Stanford University)

In 1968, Stanford University biologist Paul Ehrlich caused waves with the publication of The Population Bomb, which predicted that ​overpopulation would result in the starvation deaths of hundreds of millions of people. In an interview in 1979 with CBS News, Ehrlich said, "Sometime in the next 15 years, the end will come — and by 'the end,' I mean an utter breakdown of the capacity of the planet to support humanity."

But with the rise in technology, Ehrlich's predictions failed to materialize, says Ellis, and instead, the opposite occurred— there's less famine now, and "pretty much every indicator of human well-being" has increased since the 1970s.

"I think the fact that those results are not presented [in the article] is a fascinating statement about the purpose of this message," Ellis said.

Meanwhile, as more people move to urban, industrial societies from agrarian societies, where people tend to have more children, human population growth is expected to peak, and likely decline at the latter half of the century, Nordhaus said.

A toll on the environment

In an interview with CBC News earlier this week, Eileen Crist, a professor at Virginia Tech's department of science and technology in society and co-author of the article, said the real issue when it comes to overpopulation is the rapid rise of the global middle class. The flip side of more people being lifted out of poverty, she said, is that it's also increasing the carbon footprint on the planet and taking a toll on the environment.

Ellis agreed that the relationship between how wealth is gained and how it affects the environment needs to continue to improve. But compared to the past, we use less carbon to generate energy and less land to generate food, he said.

"We think that's the other message that we need to have out there that people need to hear: We can do this. We can pull people out of poverty and not expand our environmental footprint," he said. "It is not easy, it is not trivial, but we can do it. We can even do it with existing technology."

For some time to come, Nordhaus said, the growth in per-capita consumption will be greater than the decline in fertility rates and the slowing in population growth.

However, in the long term, that will be moderated through technology and the more efficient ways resources are turned into goods and services.

"There is a lot of good evidence that sort of demand for all sorts of material goods saturates as populations kind of industrialize and become healthier," he said.

Joel Cohen, a Columbia University mathematical biologist and demographer researching global populations, was less critical of the report, and said it's good to draw people's attention to the issues facing the planet.

"But I think this gives ammunition to people who are opposed to doing anything about these problems because it's so scaremongering," he said.

"I'm glad they've got people talking about it. I just hope it doesn't come back in their face."