Want to save the planet? Say bye-bye to nature: Column The faster we all move into nuke- and solar-powered cities, fed by corporate high-tech agriculture, the more we can protect nature.

Michael Shellenberger and Ted Nordhaus | USATODAY

Since before the first Earth Day in 1970, environmentalists have argued that solving environmental problems required humans to get closer to nature. The "back to the land" movement urged people to leave cities, which were viewed as crowded and polluted. Renewable energy was recommended because it integrates human civilization into natural energy flows, such as water, biofuels and the sun. Similarly, organic agriculture was better because it integrated farmers and consumers into the natural rhythms of nature.

In recent years, though, a growing number of environmental scientists and activists are saying that the best way to protect nature is not by returning to it, but rather by leaving it alone.

Today, most environmentalists embrace cities and reject suburban sprawl. Where cities take up just 1%-3% of the Earth's ice-free surface, farms take up about 40%. Cities simply allow people to use energy and other resources more efficiently. By concentrating people in a denser land area, cities free up more of the Earth for nature and wildlife.

Cities also turn out to be the key to reducing the overall size of the human population. Around the world, as people move to cities, women choose to have fewer children. That's largely because children are no longer required to work on the farm. Parents are busy working in factories or some other urban job.

As a result, the global human population will likely peak at 9 billion to 11 billion, from today's 7 billion, and then decline. How much further the human population increases depends in large measure on how quickly people can find jobs in cities in places such as sub-Saharan Africa.

For more people to live in cities, farmers who stay in the countryside will need to produce more food. While many of us have a romantic attachment to family farms, the truth is that growing more food on less land — and leaving more of the countryside to nature and wildlife — requires big farms that use fertilizer and tractors and have access to roads and electricity.

This process of agricultural modernization has already been a huge success in the USA. In the 1800s, just 30% of New England was covered with forest. Today, 80% is forested.

The reason for reforestation in the U.S. and other rich countries is not only because of agricultural intensification, but also because we stopped using wood for fuel as frequently. We built hydroelectric dams and fossil power plants, and piped natural gas into homes. We did not use wood, a "renewable resource," more sustainably, but rather drastically reduced our consumption by creating better substitutes.

The same cannot be said for the more than 2 billion people around the world who still rely on wood and dung as their primary source of energy and depend on low yield, subsistence agriculture and wildlife harvesting to feed themselves. Deep agrarian poverty is bad for both people and the environment. An estimated 4 million people die every year from inhaling smoke from wood and dung alone. And when people depend on wild animals ("bushmeat") for protein, and on wood and charcoal for fuel, they hunt local wildlife to extinction, and degrade their forests for energy.

In the United States and Europe, by contrast, we depend far less on nature anymore for our material well-being. Modern energy, mostly fossil fuels, has liberated people from the environment and the environment from us. The same improvements to agriculture that have allowed our forests to come back have also freed nearly all of us from back-breaking labor.

Fossils fuels and modern agricultural practices today cause many problems, including air and water pollution as well as global warming. Even so, we should not forget the benefits they have brought. Looking forward, we should move to cleaner energy sources that use fewer natural resources.

But protecting the environment and saving more nature in the 21st century will not require that we get closer to nature. Rather, it requires that we get farther from it, through better technologies. Getting off of fossil fuels will require that we shift to better energy technologies, such as nuclear and solar energy which are clean, power-dense and abundant. Growing more food on less land with fewer environmental impacts will require better seeds, fertilizers, pesticides, and things such as vertical greenhouses and laboratory meat that make us less dependent on land and water to grow food.

Ultimately, nature made useless is nature spared. On this 45th anniversary of Earth Day, let us resolve to leave nostalgic dreams of recoupling with nature behind and embrace instead an ecologically vibrant future in which all of humanity thrives by increasingly leaving nature alone.

Michael Shellenberger and Ted Nordhaus, co-founders of the Breakthrough Institute, are co-authors of "An Ecomodernist Manifesto."

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