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vast majority of people are much better fed, much better sheltered, much better entertained, much better protected against disease and much more likely to live to old age than their ancestors have ever been.” He continues: “This generation of humans has access to more calories, watts, lumen-hours, square feet, gigabytes, megahertz, light-years, nanometres…” (the list goes on for a while) “…tennis rackets, guided missiles and anything else they could even imagine needing.” Nor is the global inequality frequently bemoaned by leftists much of a fly in the ointment: “The average Botswanan earns more than the average Finn did in 1955. Infant mortality is lower today in Nepal than it was in Italy in 1951.”9 And so on.

Where I disagree with Ridley and many of his colleagues on the right is their tendency to then go on to downplay or deny the environmental consequences of this human great leap forward, as later chapters will show. For Ridley in particular, his determination to show that the party can go on forever has led him to stray into very unscientific stances on issues covered in this book like climate change and ocean acidification. Why not just admit candidly that while the human advance has been amazing and hugely beneficial, it has also had serious environmental impacts? As this book shows, Earth system boundaries can now increasingly be defined scientifically, and our job as modern, knowledgeable humans is to use all the tools at our disposal to avoid trespassing over these boundaries—at the same time as we must seek to allow the growth in human prosperity and numbers to continue for the foreseeable future.

For land in particular, our impacts on the planet’s terrestrial surface are now so extensive and transformative that they threaten the capacity of varied ecosystems to self-regulate and maintain the living biosphere overall. Natural landscapes filter water, produce oxygen, sequester carbon, and provide vital habitat for other species. Whether these landscapes harbor forests, wetlands, grasslands, or even deserts, the planet’s varied biomes are an integral part of the Earth system—and are essential to its continued sustainable functioning.

Computer models of the Earth system can demonstrate how varied ecological zones are important to the planet overall. In one modeling study, climatologist Peter Snyder and his colleagues tried deleting entire biomes from their simulated planet to see what then happened to the climate. Remove the savannahs, they found, and you reduce rainfall totals by a third.10 Press the delete key over the tropical forests, and entire continents see dramatic reductions in their precipitation and sudden rises in temperature. Different biomes, from temperate forests to the Arctic tundra, likely have significant effects on winds, temperatures, and atmospheric circulation patterns.

As more and more of the Earth’s surface sees these traditional biological zones transformed into “anthropogenic biomes” dominated by humans, Earth-system scientists expect the planet’s functioning to become steadily more unstable. Across at least three-quarters of the world today, humans are as or more important in determining which species make up the ecosystem than previously dominant factors like latitude, climate, and geography.11 Instead of the neat green and yellow strips that we learned about in geography class, denoting jungle, desert, and so on, the planet is now divided into a complex mosaic of different human-influenced ecosystems. Human capture of the planet’s productive capacity, according to the most recent relevant study, now adds up to about 24 percent of the total productivity of the Earth’s terrestrial biosphere.12 In other words, a quarter of everything produced by all plants on land is eaten or otherwise consumed by us.

Different landscapes are exploited with different intensity: While forests will yield up to a fifth of their annual production in fuel, fiber or timber, cropland allows us to grab an impressive 83 percent of the yearly productive share per hectare. The human species, therefore, while