THE 1992 “Earth Summit” succeeded in alerting the conscience of the world to the urgency of achieving environmentally sustainable development. We know enough to act today, but we must also find answers to the many tough conceptual and technical questions that remain.
As last year’s “Earth Summit” in Rio de Janeiro drew to a close, its message to the world became clear: without better environmental stewardship, development will lx- undermined, and without accelerated development in poor countries, environmental policies will fail. The evidence is all around us In sub-Saharan Africa, “slash and burn” approaches to agriculture—in the face of rising population growth—are creating vicious cycles of soil degradation and impaired productivity. In cities like Sao Paulo, Mexico City, and Bangkok, the polluted air and water are posing a serious health threat. Industrial country emissions of greenhouse gases—threatening a 2—4° centigrade rise in global temperatures over the next century—show little sign of abatement.
Rio was a signal to the world that after decades of pitting environmental quality against economic growth, policymakers are finally becoming aware of the crucial and potentially positive link between the two. Humanity must learn to live within the limitations of the physical environment as both a provider of inputs and a “sink” for waste. We must recognize that even if environmental degradation does not reach life-threatening levels, it can result in a significant decline in the quality of the world we live in. We must face our responsibilities to other species and the need to protect biodiversity. We must find a way to enable all people, now and in the future, to enjoy clean water, clean air, and fertile soils.
But basic as these concerns may seem, the world today faces a tremendous backlog in providing these basic amenities to the poor and disadvantaged. One billion people—mostly in developing countries—do not have access to clean water, 1.7 billion people do not have access to sanitation, and 2–3 million children die annually because of diseases associated with this lack of water and sanitation. To this situation, we are adding about 90 million people to the global population every year—again, mostly in developing countries. This raises huge challenges for policymakers as they seek to reconcile the needs and aspirations of the growing population with the limitations of the natural world. Three particular challenges stand out:
Food production. As the world’s population expands to 9 billion over the next 40 years, food consumption will double. Even though the required rate of growth of food production—1.6 percent per year—will be less than the 2 percent achieved for the past three decades, agronomists agree that the task is likely to be much more difficult, since many of the sources of earlier growth are no longer available. Two options now exist: intensifying production on land already in use, and expanding into new areas. In the past three decades, intensification has dominated, accounting for over 90 percent of agricultural growth. Whether a new “green revolution” will be able to repeat the remarkable gains in yields is highly uncertain. The challenge will be not only to raise yields but to do so in a less damaging way than in the past. Already, the environmental problems of intensification (chemical and biological runoff, water logging, salinization, and the like) are serious in some areas and, without better policies, will get much worse.
Urbanization and pollution. Ninety percent of the world’s increased population will be located in urban areas, posing formidable problems of social and institutional change, infrastructure investment, and pollution control. Already many municipal authorities are overwhelmed by their current responsibilities’—yet the task ahead will only increase. Making clean water available to everybody in the next 40 years will require extending service to 3.7 billion more urban residents. And preventing pollution from worsening in some fast-growing countries will require that pollution per unit of industrial output fall by 90 percent between now and 2030.
Human encroachment. As human numbers and the scale of their activities increase, so does the pressure on fragile ecosystems. In the past decade, 7–10 percent of tropical forests and wetlands have been destroyed, important aquifers have been depleted, and coastal zones have been polluted at an unprecedented rate. We now know that income growth need not cause these problems and can help reduce them. But without better policies, the coming decades will witness even worse damage.