Here's an article by
Scientific American;
''In an era of changing climate and sinking economies, Malthusian limits to growth are back—and squeezing us painfully. Whereas more people once meant more ingenuity, more talent and more innovation, today it just seems to mean less for each. Less water for every cattle herder in the Horn of Africa. (The United Nations projects there will be more than four billion people living in nations defined as water-scarce or water-stressed by 2050, up from half a billion in 1995.) Less land for every farmer already tilling slopes so steep they risk killing themselves by falling off their fields. (At a bit less than six tenths of an acre, global per capita cropland today is little more than half of what it was in 1961, and more than 900 million people are hungry.) Less capacity in the atmosphere to accept the heat-trapping gases that could fry the planet for centuries to come. Scarcer and higher-priced energy and food. And if the world’s economy does not bounce back to its glory days, less credit and fewer jobs.''
''Population growth constantly pushes the consequences of any level of individual consumption to a higher plateau, and reductions in individual consumption can always be overwhelmed by increases in population. The simple reality is that acting on both, consistently and simultaneously, is the key to long-term environmental sustainability. The sustainability benefits of level or falling human numbers are too powerful to ignore for long.''
A Number of Us
Two big questions present themselves as population reemerges from the shadows: Can any feasible downshift in population growth actually put the environment on a more sustainable path? And if so, are there measures that the public and policy makers would support that could actually bring about such a change?
Nature, of course, couldn’t care less how many of us there are. What matters to the environment are the sums of human pulls and pushes, the extractions of resources and the injections of wastes. When these exceed key tipping points, nature and its systems can change quickly and dramatically. But the magnitudes of environmental impacts stem not just from our numbers but also from behaviors we learn from our parents and cultures. Broadly speaking, if population is the number of us, then consumption is the way each of us behaves. In this unequal world, the behavior of a dozen people in one place sometimes has more environmental impact than does that of a few hundred somewhere else.
''Consider how these principles relate to global warming. The greenhouse gases already released into the atmosphere are likely to bring us quite close to the 3.6 degree F (two degree C) increase from the preindustrial global temperature average that many scientists see as the best-guess threshold of potential climate catastrophe. Already the earth is experiencing harsher droughts, fiercer storms and higher sea levels. If the scientists are right, these impacts will worsen for decades or centuries. Indeed, even if we ended all emissions tomorrow, additional warming is on the way thanks to the momentum built into the earth’s intricate climate system. (The oceans, for example, have yet to come into equilibrium with the extra heat-trapping capacity of the atmosphere. As the oceans continue to warm, so will the land around them.)''