The Earth and us
Many a literary metaphor contrasts the unvarying Earth with the fast-flowing fortunes of people. If you've read this far in the book, you'll know that this is inaccurate. Weather systems, sea levels, ice sheets and river courses change over time, in some cases surprisingly quickly. Of course, the solid Earth is made of sterner stuff and changes more slowly. But eventually, mountains are worn away, oceans open and close and continents are swallowed up. In some parts of the world, earthquakes and volcanoes can remake landscapes in days.
What is true is that the Earth is a lot less unvarying than it used to be. In recent times, a new and vigorous Earth-altering force has emerged that transforms its surroundings over years rather than millennia. Yes, I am talking about you.
People have always changed their environment. But in recent centuries, things have become much more serious. Part of the issue is a simple question of population. A couple of thousand years ago, Jesus was one of about 300 million people at most. In 1800 there were 900 million humans, and in 1900,1.6 billion. Now there are over 6 billion of us, compared to only about 200,000 of our nearest relative, the chimpanzee Pan troglodytes. The other reason for our increasing domination is technology and the speed it adds to human action. We are able to use more land, water, minerals and other resources than we could even a few centuries ago. It takes a forest decades to spread a few kilometres, but people need only a few days to cut it down.
This combination of a burgeoning population and increasing impact per person means that the Earth is turning into a unique case, as far as we know, of a planet that is consciously managed by a single self-ware species.
It is best not to get carried away by this idea. Despite the sway humanity now has over large areas of the Earth, it would be wrong to think that we have it under any sort of control. The increasing death toll from natural disasters makes it clear that we are far from being in control of the inanimate world. And as the constant flow of new infectious diseases shows, from HIV and Ebola to each winters new flu, nature is still tougher than we are and is producing new forms of life the whole time. Indeed, our new technologies have actually aided the global proliferation of diseases.
It is now possible to get from one side of the world to another in a day, which is less than the incubation time of many diseases, and new forms of influenza and other diseases make the most of this, getting from Asia to Europe or the US with little warning. If you live near a European airport with frequent flights to Africa, you can get “airport malaria” from mosquitoes that have arrived by plane. More serious plant and animal diseases take advantage of the increased world trade in meat, vegetables, pets and livestock to spread around the globe. Even in the city, humans are not in total charge of their environment and share it with other species, something I am reminded of every few days in inner London when I see a fox in the garden.
However, although we may not always have the upper hand, were certainly making our mark on the world around us. Much of the attention that is paid to our impact on the Earth is currently focused on the question of human-induced climate change. Another issue of serious concern is the number of species that we are driving to extinction. We will look at both of these issues in due course, but first we are going to consider a more fundamental question, which will quantify our dominance of the planet in percentage terms: how much of the Earth and its resources are we exploiting for our own purposes?