Analysts predict that there will be one billion vehicles on the world's roads in 2025. Most of this increase will come as the LDCs improve their standard of living. There are in the United States about 750 vehicles for every 1,000 people. By contrast, for every 1,000 people, China has only eight vehicles and India just seven. Even the 650 million vehicles being driven today emit an immense amount of CO 2 .
Trees are another part of the equation.
They are the environmental antithesis of vehicles in that they convert CO 2 to oxygen. Unfortunately for the atmosphere, the number of trees have been decreasing as vehicles have been increasing. As noted earlier in this chapter, the forests that remain today are only about half the size of the forests that once were. Inasmuch as a large tree can absorb and convert up to 48 pounds of CO 2 into oxygen annually, the loss of billions of trees has vastly diminished the ability of the Earth to cleanse itself of excess CO 2 . What is complex is how to balance the equation, that is, how to achieve sustainable development.