How Many Species Will Survive the 21st Century?

In our 4.5 billion year old world, human beings have been present for perhaps 2 million years. Our ancestors invented agriculture about 11,200 years ago, probably in or near central Turkey. At that time, they lived in small groups of hunter-gatherers, with the total global human population estimated at 3 – 4 million people. They did certainly use plants directly as medicines, as do two thirds of the people in the world today. With the ability to produce large amounts of food and store food it, the human population began to grow, so that at the time of Christ they were approximately 300 million people worldwide, 1 billion for the first time in about 1820, and more than 7 billion today. There are three people alive for each one who was living when I was born in the mid-1930 s, heading at a net addition of about 200,000 people per day to an estimated 9.5 billion people by mid-century. Consumption levels per individual are rising even more rapidly than population, even though more than 1 billion of us are hungry. We are using more than 150 per cent of what the world can produce (http://www.footprintnetwork.org) and so are inflicting great harm on the potential sustainability of the planet.

As a result of this pressure, habitats are being destroyed worldwide; invasive plants, animals, pests, and pathogens are spreading rapidly; many species are being over-harvested in nature, and global climate change is altering conditions and hence possibilities for survival worldwide. What survives depends very directly on us. I estimate that there may be some 12 million species of organisms other than bacteria and viruses, but only 1.9 million have actually been detected and named, and we know next-to-nothing about most of them (one specimen, for example). We are giving names to newly discovered ones at a rate of about 10,000 per year, and probably, in a situation where the rate is accelerating, losing them faster than we are naming them. Giving the increasing rate of biological extinction, the remainder of this century could see the loss of more than half of the biological diversity than exists. What is saved, what is lost, what we chose to do, what is possible? The answers to these questions will determine the actual result, and they in turn depend on us.