重點在自然資源與維持人口數目所需的資源是否相當。


Influential Ecologist Predicts Human Population Will Collapse This Century

We've heard this argument before.

Ross Pomeroy, 10/30/23

* Esteemed ecologist William Rees argues that humanity is in a state of ecological overshoot, using far more resources than the Earth can sustainably provide over the long term. When this happens to other species, there is a population "correction." 
* Mainstream opinion disagrees with his take. Demographers at the UN predict that — due to a combination of higher standards of living, birth control, and shifting perspectives on sustainability — the human population will peak in the mid-2080s and then decline slowly. 
* Others before him, notably Thomas Malthus in 1798 and Paul Ehrlich in 1968, made similar predictions. Reality proved them wrong.

For 99.9% of Homo sapiens‘ 250,000 years on planet Earth, our population has remained below one billion individuals, and for much of that time, our species’ growth curve was relatively flat. Since 1800, however, the human population has exponentially ballooned to 8.1 billion from just under one billion. We now occupy almost all parts of the globe and ravenously consume resources beyond what Earth can sustainably provide for the long term.

As eminent ecologist William E. Rees argues in an ominous new paper, this is a recipe for impending disaster.

Boom and bust cycles

For 40 years, Rees taught at the University of British Columbia, focusing on planning related to global environmental trends and sustainable socioeconomic development. His most notable academic contribution is the concept of the “ecological footprint,” the “amount of environmental resources needed to produce the goods and services that support an individual’s lifestyle.”

As an ecologist, Rees is well aware that all sorts of species frequently go through boom and bust cycles. When resources are plentiful and threats are low, they reproduce and multiply. But when resources dry up, perhaps from over-consumption or environmental change, species’ populations will precipitously fall.

Rees’ painfully simple proposition in his new paper is that humans are no different from any other species. Thus, we are just as vulnerable to population busts as we are prone to booms. “Homo sapiens is an evolving species, a product of natural selection and still subject to the same natural laws and forces affecting the evolution of all living organisms,” he wrote.

And make no mistake, we are at the peak of a boom on the precipice of a bust, he says. Human population’s 700% rise, along with a 100-fold expansion of real world product, over the last two centuries are anomalies unlocked by rampant use of fossil fuels, deforestation, mining, and arable land destruction. This has propelled us into an ecological state of “overshoot,” where we are consuming more resources than can be replenished and producing more waste than can be handled by ecosystems. The only question is when humanity’s bubble will collapse. Rees portends it will happen in our lifetimes.

“The global economy will inevitably contract and humanity will suffer a major population ‘correction’ in this century,” he wrote.

A population “correction”

How bad will it be? Rees cites estimates suggesting that the number of humans that Earth can support for the long term is between 100 million and 3 billion people. So, the population and civilization collapse he forecasts will be quite bad, indeed. He even briefly painted a bleak picture of how it might happen.

“As parts of the planet become uninhabitable, we should expect faltering agriculture, food shortages, and possibly extended famines. Rising sea levels over the next century will flood many coastal cities; with the breakdown of national highway and marine transportation networks other cities are likely to be cut off from food-lands, energy, and other essential resources. Some large metropolitan areas will become unsupportable and not survive the century.”

After the population correction, Rees portends a more primitive future.

“It may well be that the best-case future will, in fact, be powered by renewable energy, but in the form of human muscle, draft horses, mules, and oxen supplemented by mechanical water-wheels and wind-mills.”

A false prophet of doom?

Rees’ opinion is not destiny, of course. If it sounds familiar, it’s because much of it is simply a rehashed version of what Paul Ehrlich wrote in 1968 in his book The Population Bomb. Thomas Malthus made the same argument in 1798. For the past 225 years, reality has proven them wrong. There is no convincing evidence to suggest that conditions on Earth have changed so much that a human population collapse is inevitable or even likely. Indeed, as productivity has increased and technology has advanced, we are creating more things but using fewer resources.

Besides, demographers at the United Nations forecast that the human population will peak in the mid-2080s at around 10.4 billion people, after which it will level off and decline. Rather than due to a catastrophic collapse, this natural slow-down will be the result of higher standards of living, birth control, and shifting perspectives on sustainability, among other reasons. In short, the UN, along with most other scientists, predict that humans will effectively choose to dwindle in number rather than have the choice made for us in dramatic and deadly fashion.

In places, Rees’ paper reads like the rantings of a dour old ecologist, understandably angered by the damage humanity has done to the natural world. Sprinkled throughout the article are opinionated barbs aimed at various targets: short-sighted politicians, naive techno-optimists, and overly hopeful scientists. He also reserves a fair amount of irritation for those who insist that climate change is the greatest problem that humanity faces, when the real problem is us — or rather too many of us.

Still, Rees’ arguments should not be ignored entirely. The accomplished ecologist has distinguished himself through decades of scholarship. He also draws on history to correctly note that many major civilizations throughout human history have collapsed and suffered die-offs, often stemming from ecological overshoot within their respective habitats. He believes that, if we aren’t careful, the same will happen again. Let’s be sure to prove him wrong.