Land-Use and Land-Cover Change: Advances in 1.5 Decades of Sustained International Research

exceeded anything that the Earth has experienced for millions of years, and the growth rate has been unprecedented. But such long-term views are sometimes hard to grasp. What is the timescale relevant for society today? Perhaps it is more instructive to consider just the period over which civilization has developed, from the time when the first cities were established around 6000 years ago. If we consider this in terms of the minute hand on a clock, with time ticking away as we approach the present, each minute represents a century (Figure 3). 6000 years ago, CO2 levels were around 270ppmv. When the first writing was developed, around 3800 years ago (20 minutes to the hour in terms of the "civilization clock") CO2 levels were still close to 280ppmv ... and they remained at this level throughout most of our history – throughout Egyptian and Chinese, Incan and Mayan dynasties, all through the Crusades, the Inquisition, the Renaissance and the period of European settlement of the New World. But things began to change significantly following James Watt's invention of the steam piston engine 250 years ago, and Karl Benz and Gustav Daimler's introduction of the first petrol-driven internal combustion engines in 1886 – a little over 100 years ago and only 2 or 3 minutes ago on our clock of civilization. As we began this process of industrialization, CO2 levels were 275ppmv ... but today they have reached 360ppmv and are rising rapidly. Thus, on the time-scale of this clock of civilization it's the last 2 minutes where things have gone badly wrong on a global scale ... and it's in the "next minute" – that is, within this century – that we must fix the problem. We cannot mindlessly hand it off to our children, and to future generations as yet unborn, with the hope that