完形填空 　Our world of the mid-1990s faces potentially bursting change. The question is in what direction will it take us? 46) Will the change come from worldwide initiatives that reverse the degradation of the planet and restore hope for the future, or will it come from continuing environmental deterioration that leads to economic decline and social instability? 　　There is no precedent for the rapid substantial change we need to make. 47) Building an environmentally sustainable future depends on restructuring the global economy, major shifts in human reproductive behavior, and dramatic changes in values and lifestyles. Doing all this quickly adds up to a revolution that is driven and defined by the need to restore the earth''s environmental systems. If this Environmental Revolution succeeds, it will rank with the Agricultural and Industrial Revolutions as one of the great economic and social transformations in human history. 　　Like the Agricultural Revolution, it will dramatically alter population trends. 48) While the former set the stage for enormous increases in human numbers, this revolution will succeed only if it stabilizes human population size, reestablishing a balance between people and natural system on which they depend. In contrast to the Industrial Revolution, which was based on a shift to fossil fuels, this new transformation will be based on a shift away from fossil fuels. 　　49) The two earlier revolutions were driven by technological advances―the first by the discovery of farming and the second by the invention of the steam engine, which converted the energy in coal into mechanical power. The Environmental Revolution, while it will obviously need new technologies, will be driven primarily by the restructuring of the global economy so that it does not destroy its natural support system. 　　The pace of the Environmental Revolution needs to be far faster than that of its predecessors. The Agricultural Revolution began some 10,000 years ago, and the Industrial Revolution has been under way for about two centuries. But if the Environmental Revolution is to succeed, it must be compressed into a few decades. Progress in the Agricultural Revolution was measured almost exclusively in the growth in food output that eventually enabled farmers to produce a surplus that could feed city dwellers. Similarly, industrial progress was gained by success in expanding the output of raw materials and manufactured goods. 50) The Environmental Revolution will be judged by whether it can shift the world economy into an environmentally sustainable development path, one that leads to greater economic security, healthier lifestyles, and a worldwide improvement in the human condition.