How many times have you heard that we humans are "using up" the world's resources, "running out" of oil, "reaching the limits" of the atmosphere's capacity to cope with pollution or "approaching the carrying capacity" of the land's ability to support a greater population? The assumption behind all such statements is that there is a fixed amount of stuff—metals, oil, clean air, land—and that we risk exhausting it through our consumption.
"We are using 50% more resources than the Earth can sustainably produce, and unless we change course, that number will grow fast—by 2030, even two planets will not be enough," says Jim Leape, director general of the World Wide Fund for Nature International (formerly the World Wildlife Fund).
But here's a peculiar feature of human history: We burst through such limits again and again. After all, as a Saudi oil minister once said, the Stone Age didn't end for lack of stone. Ecologists call this "niche construction"—that people (and indeed some other animals) can create new opportunities for themselves by making their habitats more productive in some way. Agriculture is the classic example of niche construction: We stopped relying on nature's bounty and substituted an artificial and much larger bounty.
Economists call the same phenomenon innovation. What frustrates them about ecologists is the latter's tendency to think in terms of static limits. Ecologists can't seem to see that when whale oil starts to run out, petroleum is discovered, or that when farm yields flatten, fertilizer comes along, or that when glass fiber is invented, demand for copper falls.
That frustration is heartily reciprocated. Ecologists think that economists espouse a sort of superstitious magic called "markets" or "prices" to avoid confronting the reality of limits to growth. The easiest way to raise a cheer in a conference of ecologists is to make a rude joke about economists.
In the climate debate, for example, pessimists see a limit to the atmosphere's capacity to cope with extra carbon dioxide without rapid warming. So a continuing increase in emissions if economic growth continues will eventually accelerate warming to dangerous rates. But optimists see economic growth leading to technological change that would result in the use of lower-carbon energy. That would allow warming to level off long before it does much harm.
It is striking, for example, that the Intergovernmental Panel on Climate Change's recent forecast that temperatures would rise by 3.7 to 4.8 degrees Celsius compared with preindustrial levels by 2100 was based on several assumptions: little technological change, an end to the 50-year fall in population growth rates, a tripling (only) of per capita income and not much improvement in the energy efficiency of the economy. Basically, that would mean a world much like today's but with lots more people burning lots more coal and oil, leading to an increase in emissions. Most economists expect a five- or tenfold increase in income, huge changes in technology and an end to population growth by 2100: not so many more people needing much less carbon.
In 1679, Antonie van Leeuwenhoek, the great Dutch microscopist, estimated that the planet could hold 13.4 billion people, a number that most demographers think we may never reach. Since then, estimates have bounced around between 1 billion and 100 billion, with no sign of converging on an agreed figure.
Economists point out that we keep improving the productivity of each acre of land by applying fertilizer, mechanization, pesticides and irrigation. Further innovation is bound to shift the ceiling upward. Jesse Ausubel at Rockefeller University calculates that the amount of land required to grow a given quantity of food has fallen by 65% over the past 50 years, world-wide.
Ecologists object that these innovations rely on nonrenewable resources, such as oil and gas, or renewable ones that are being used up faster than they are replenished, such as aquifers. So current yields cannot be maintained, let alone improved.
In his recent book "The View from Lazy Point," the ecologist Carl Safina estimates that if everybody had the living standards of Americans, we would need 2.5 Earths because the world's agricultural land just couldn't grow enough food for more than 2.5 billion people at that level of consumption. Harvard emeritus professor E.O. Wilson, one of ecology's patriarchs, reckoned that only if we all turned vegetarian could the world's farms grow enough food to support 10 billion people.
The best-selling book "Limits to Growth," published in 1972 by the Club of Rome (an influential global think tank), argued that we would have bumped our heads against all sorts of ceilings by now, running short of various metals, fuels, minerals and space. Why did it not happen? In a word, technology: better mining techniques, more frugal use of materials, and if scarcity causes price increases, substitution by cheaper material. We use 100 times thinner gold plating on computer connectors than we did 40 years ago. The steel content of cars and buildings keeps on falling.
Until about 10 years ago, it was reasonable to expect that natural gas might run out in a few short decades and oil soon thereafter. If that were to happen, agricultural yields would plummet, and the world would be faced with a stark dilemma: Plow up all the remaining rain forest to grow food, or starve.
But thanks to fracking and the shale revolution, peak oil and gas have been postponed. They will run out one day, but only in the sense that you will run out of Atlantic Ocean one day if you take a rowboat west out of a harbor in Ireland. Just as you are likely to stop rowing long before you bump into Newfoundland, so we may well find cheap substitutes for fossil fuels long before they run out.
In 1972, the ecologist Paul Ehrlich of Stanford University came up with a simple formula called IPAT, which stated that the impact of humankind was equal to population multiplied by affluence multiplied again by technology. In other words, the damage done to Earth increases the more people there are, the richer they get and the more technology they have.Many ecologists still subscribe to this doctrine, which has attained the status of holy writ in ecology. But the past 40 years haven't been kind to it. In many respects, greater affluence and new technology have led to less human impact on the planet, not more. Richer people with new technologies tend not to collect firewood and bushmeat from natural forests; instead, they use electricity and farmed chicken—both of which need much less land. In 2006, Mr. Ausubel calculated that no country with a GDP per head greater than $4,600 has a falling stock of forest (in density as well as in acreage).
Haiti is 98% deforested and literally brown on satellite images, compared with its green, well-forested neighbor, the Dominican Republic. The difference stems from Haiti's poverty, which causes it to rely on charcoal for domestic and industrial energy, whereas the Dominican Republic is wealthy enough to use fossil fuels, subsidizing propane gas for cooking fuel specifically so that people won't cut down forests.
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