The Parable of Isle Royale

Isle Royale in Lake Superior is a national park. Besides its fame as a park, Isle Royale is also famous for its wolf and moose populations. The island provides a unique experimental design of what happens when populations are permitted to grow without restraint.

The story begins with the immigration of moose to the island sometime in the late 1800s or early 1900s.  Some speculate that moose swam to the island or crossed on ice in winter. No matter how they got there, they existed on the island for five decades without wolves. By the 1920s the moose population increased to more than 3000 and as a consequence of over browsing, the moose population crashed in the 1930s. The moose population languished for a while, and then began to grow again.

Just after World War II, wolves migrated to the island, most likely over the ice in winter. Wolves preyed on moose, and for a few decades, wolves and moose seems to sustain a relative equilibrium. Then in 1980, the wolf population crashed after the introduction of canine parvovirus.

Released from wolf predation, the moose population soared to new heights inflicting tremendous damage to the island’s plant communities. As before the moose population crashed with 2000 moose starving to death in one four month period! The moose population now remains at around 500 animals, far below their original high numbers due to the damage sustained by the island’s plant community as a consequence of too many moose.


There are lessons for human population in the Isle Royale example as well as other tales that could be told. Continuous population growth can lead to habitat degradation, great suffering for the dominant animal, and eventually a lowered carrying capacity due to habitat destruction.

Human populations may be like the proverbial moose population. We have been released from predators that might otherwise keep our numbers in check and somewhat sustainable. Mind you I have no wish for a major pandemic, famine, warfare or other factors that once held human numbers in check. But I do think there are plenty of signs, that humans, like the moose of Isle Royale, are degrading the carrying capacity of Planet Earth—which is, after all, the only habitable island we know of in the Universe.

Despite the seriousness of population growth as an agent of planetary damage with serious potential repercussions for human survival, there is a tendency for the majority of people to ignore the issue.

There are many on both the left and right ends of the political spectrum who feel human population growth is not a problem or at the very least a manageable problem. Typically the right opposes any discussion of population reduction because of conservative religious views or a business model that requires endless growth to maintain economic prosperity. The left tends to downplay population based on social justice grounds—that the world’s poor are blamed for population growth, while the world’s richest countries enjoy the benefits of excessive consumption.

Both support their respective positions often by arguing that as a result of technology we will  rise to the occasion and help us get through any shortages we may face be it energy, food, or space. In a sense the worldviews of the left and right are not appreciably different when it comes to techno optimism.

I am inclined to agree that technological advances often change assumptions about limiting factors—what’s available to use and at what cost can change dramatically due to technological innovations. At one time salt was more valuable than gold, but technological innovations has made it so common we can buy it for pennies.  So I am loath to discount how technology can rapidly change predictions and assumptions about the availability of critical resources.

But the problem is that technology does not come free. There’s a huge ecological cost to technological fixes. Even if you could grow sufficient food for 10 billion people, one has to consider what’s driving that food production. The price of food does not reflect the real costs.

It’s the mining that produces the metal to make the plow. It’s the gas drilling that provides the fertilizer. It’s the oil drilling that provides the fuel to power the trucks that moves the food to people. It’s the dams that provide the water storage for irrigation of fields.  And even more so today the computers that calculate the amount of water to spread or the exact percentage of pesticide to apply and so on. Behind that food production is long technology train that is pulling a lot of cars—each taking a bite out of the Earth’s biodiversity, land and water to feed a growing human population.

Of course, I’m generalizing here, and there are many shades of gray and degrees of buy-in to the various perspectives. But there are few on either side of the right or left who agree that human population growth poses a grave danger to the Earth’s ecosystems and biodiversity, much less a threat to humanity as well.

The debate over population has largely focused on whether outright population growth—primarily in the less developed countries is a threat– and/or whether consumption of natural resources by developed countries is really the problem for sustainability. In reality this debate is not helpful since both are problematic.  Both issues need to be addressed.  Depending on how you define sustainability, we are already likely well past any sustainable society.


There are physical limits to the Earth and its life support systems.  And though technology can unleash abundance where previously there was scarcity, ultimately this means there are limits to population growth. There is only so much agricultural land, fish in the sea, fresh water to drink, oil and coal to burn, and so forth. Where and when we reach those limits is a matter of debate, and for many of these resources, limits may be more regional in nature. But what can’t be debated is that all of these are finite.  I don’t doubt that humans are clever and innovative, and some of these resources will be replaced or used far more efficiently in the future.

Nevertheless,  just the physical need for housing, and providing basic needs for an expanding human population will place new demands on Planet Earth whether we impose strict limits or not. What we have in terms of ecological limitations is a planet that is already overtaxed if one uses the appropriate metrics like biodiversity loss.

It would be unfortunate to simply try to determine what number of humans could be supported on Earth if we were to completely exploit any of these resources.  I think it misses an important philosophical question.

In the simplest terms, some define sustainably only in terms of human population. Can the Earth sustain 10 billion or whatever number one chooses to use? I think it probably can.

However that may be the wrong question.  Human sustainability ought to be a question of quality of life. And when that is the objective, we clearly need to reduce our population and consumption. For human impacts on the planet’s natural capital; its forests, its oceans, its ecosystems, as well as air, water, air, and wildlife are already showing severe degradation and/or loss of resources that are critical to human health and happiness. Impoverishment of ecosystems, loss of biodiversity, loss of beauty and exhaustion of critical minerals, and energy supplies all threatens to jeopardize the continued habitation of humans on the planet.

Even if we could succeed in supporting a population of 9 or 10 billion people that doesn’t mean that number is good for the Earth and good for people. Do you really want to live in a mega city with wall-to-wall apartments much like a packing plant at a CAFO factory (Confined Animal Farming Operation)?  Can anyone argue that this provides a quality of life?

If one answers in the negative, and says they would prefer to live in less crowded conditions with abundant clear air, clean water, abundant wildlife, and beautiful surroundings than it really demonstrates that we must do something about population. It is a choice. Inaction is a choice by default.


There are other considerations other than merely whether human population can be sustained in some fashion. We have a moral obligation not only to the overall quality of life for humans, but also a responsibility for other life on Earth. As many have pointed out we are on the verge of a massive new extinction. The world is losing species at a rate that is 100 to 1000 times faster than the natural extinction rate. Studies have shown that biologically diverse ecosystems are more productive, so these losses, if nothing else, have the potential of reducing the ability of the Earth to sustain human population.

Habitat loss is the biggest driver of extinction. And much of this habitat loss is a direct consequence of human population growth and the need to support more and more people. For instance, agriculture already claims an astounding 40% of the Earth’s total land area. This figure is not difficult to doubt if you have ever stared out of a plane window while flying over the Great Plains and Midwest. What you see is mile upon mile—for thousands of miles—is croplands that have virtually replaced the native prairie ecosystem.

When you consider there are huge areas of permanent ice like Antarctica as well as the boreal forests that cover much of Siberia and Canada, such numbers are shocking. Agriculture, by its definition, is the production of one or a few species of plant and/or animal at the expense of native species.  And the amount of land devoted to agriculture is expanding as a direct result of human population growth. The existing agricultural land use is a major driver of species extinction and biodiversity loss. Increasing agricultural conversion will likely hasten biodiversity losses.

No one wants to say to anyone that they have to suffer hunger or even starvation. And it seems sensible to suggest that population reduction is really the only way we can guarantee adequate nutrition for people without continuing to drive more and more species over the brink to extinction.

And even when species are not driven to extinction, they may be so reduced that they are functionally extinct. Globally, large predators have been shown to have significant influence upon ecosystem function. Yet large predators are among the most imperiled animals on the Earth. In many parts of the world they are functionally extinct.


Thus far I’ve mostly made the argument for population reduction based on how it might improve things for human society. But humans are not the only species on the Planet.  Ethically we have a moral obligation to share the Planet with other life. I recognize that most people will see human life as most important, and that is completely natural. Yet it’s also an important human trait that we have compassion for other lifeforms. And if one feels that we have a moral obligation to share the Earth with the other millions of species inhabiting the Earth and being an agent of their extinction is morally wrong than we should look again at how population growth is contributing to species extirpation.


Proponents who discount population growth or suggest that the rising tide of humanity is already self- correcting and that globally population growth is tapering off.  Tapering off isn’t good enough. While some countries are experiencing reduced fertility and in some places like northern Europe or Japan, population growth is no longer at replacement, globally human population is still growing at an astounding rate.

Despite these positive shifts in demographics in some countries, we are still adding 80 million people to the Earth every year!  And some suggest that somewhere on the planet we’ll be building the equivalent of a city of a million inhabitants every five days from now until 2050. This multiplier effect due to demographic  inertia will cause significant population expansion for decades to come.

A good example is the country of Ghana. In 2010 there were 20 million people in this impoverished country.  The average number of children born per woman was 4. Even if the fertility level decreased dramatically to replacement rate of 1.1 children per mother 2020, we would see Ghana’s population continue to grow for 40 more years before it would stabilize at 40 million.

There are additional social issues, particularly concerning pregnancy and women’s health. An alarming 1400 Afghanistan women per 100,000 die in childbirth or complications from pregnancy, compared to 5 deaths per 100,000 in countries like Denmark. Of course, that is mostly a factor of poverty and lack of good medical care, but it is also a factor of how many children women in each country typically have. The more children you birth, the higher the chances that one of them will be problematic. Maintaining and providing good medical care while your population is exploding is difficult if not impossible as well.

As many note, education of women can significantly reduce population growth.  But there is a chicken and egg situation here.  One of the main barriers to education is poverty. In poor countries providing even a minimum education for women is made more difficult by the sheer number of children requiring schooling.

Happy pronouncements that we can feed more people through new agricultural techniques and other techno-fixes, ignore the fact that more a billion people already live in extreme poverty. It’s difficult to see how adding 2-3 billion more people can make it any easier to relieve poverty.

There is evidence that overall mortality and absolute poverty are declining, especially for the world’s poorest people. However, with that decline in mortality and economic growth come new demands upon the Earth.

Despite the fact that some parts of the world consume the bulk of natural resources, per capita consumption is increasing even among the poorest people. While this is likely a good thing given the extreme poverty, it does not bode well for the Earth.

In addition, most assertions that we can feed, house, cloth, educate, and employ 9 or 10 billion people requires continuing ever deeper into dependency on high tech solutions and massive inputs of energy. Intensive agriculture using genetically modified crops, an abundance of pesticides, irrigation, and the conversion of more and more the Earth’s surface to growing crops at the expense of native ecosystems.  We are already nearing the limits or perhaps exceeding the limits on what can be captured by nets and trollers from the world’s oceans. Decline in larger fish across the world has serious implications for ocean ecosystems. And most of the world’s grazing lands are suffering from livestock induced degradation, soil erosion, and weed invasion.

And unless one presumes everyone is going to live a bare existence lifestyle, providing even a reasonable amount of light, heat, and power for production and transportation of “things” requires more and more energy production.  Whether this is derived from burning of more fossil fuels or nuclear energy and/or massive wind farms, solar fields, hydroelectric, and other more renewable energy sources, the end result is more and more of the Earth is mined, drilled, and/or converted to energy production.


Part of the hysteria over population voiced by some is that declining population growth will lead to economic stagnation. As one commentator said recently “ It’s an irony that aging doomsayers like Ehrlich and Holdren may not live long enough to behold  come to fruition in their lifetime, but to achieve the very goals they claim to be aiming toward, there may be only one hope for the human species: Bring on the babies. “

The Population Reference Bureau reported that in 2011 US population grew by just 0.7%. Immigration was down, and more people survived than were born. This is causing some to wring their hands over what is sometimes called the demographic decline. They predict that aging population and lack of births will lead to economic decline and a collapse of society. Just look at the aging population of Japan and its slowing economy we are told, ignoring the fact that Germany and a number of other European countries have low reproduction rates as well as strong economies.


I’m generally an advocate of natural regulation—or letting nature take its course. But when it comes to human population collapse, I’d rather see alternatives. We are, we are told by those who suffer from too much hubris, (often the same ones saying we don’t have a population problem) that we are clever and intelligent. Well an intelligent person, and even one that might not believe we have a serious population problem, would at least use the precautionary principle which says in the absence of better information you seek the alternative that has the least potential for long term damage.

Certainly advocating population reduction can have few down sides that I am aware of, especially if done with a sense of justice and fairness. Even though I do not want to be viewed as a techno optimist, I have to admit that we have the “technology” in the form of birth control, plus education, and access to medical facilities to limit our population. It seems in light of the on-going biodiversity loss as well as other crisis’s exacerbated by population growth (like global climate change) that we can begin a global effort to bring human population more in line with global carrying capacity. And global carrying capacity in my view means not significantly contributing to accelerated species extinction, excessive pollution, and the rapid consumption  and/or degradation of finite resources.

I’m afraid that if we don’t use our brains, we’ll follow a path much like the Isle Royale moose—a major population crash with a much depressed and infinitely poorer surviving population of humans. But even worse, we may be taking down a lot of the Earth’s heritage of diversity and landscapes in the process.

George Wuerthner is an ecologist with among others, a degree in wildlife biology, and is a former Montana hunting guide. He has published 35 books. 

George Wuerthner has published 36 books including Wildfire: A Century of Failed Forest Policy