UP TO now, the Earth has been very kind to us. Most of our achievements in the past 10,000 years - farming, culture, cities, industrialisation and the raising of our numbers from a million or so to almost 7 billion - happened during an unusually benign period when Earth’s natural regulatory systems kept everything from the climate to the supply of fresh water inside narrow, comfortable boundaries.

This balmy springtime for humanity is known as the Holocene. But we are now in a new era, the Anthropocene, defined by human domination of the key systems that maintain the conditions of the planet. We have grabbed the controls of spaceship Earth, but in our reckless desire to “boldly go”, we may have forgotten the importance of maintaining its life-support systems.

The demands of nearly 7 billion humans are stretching Earth to breaking point. We know about climate change, but what about other threats? To what extent do pollution, acidifying oceans, mass extinctions, dead zones in the sea and other environmental problems really matter? We can’t keep stressing these systems indefinitely, but at what point will they bite back?