The past

The past 100 years have brought unprecedented gains in many of the indicators that we use to gauge progress in human development, from life expectancy to per capita income to education.
During the same period, however, human impact on the natural world has risen dramatically as the scope and intensity of human activities ha sincreased. Although there has been progress recently in tackling air and water pollution problems in some countries, many negative trends, such as the loss of tropical forests and the buildup of greenhouse gases in the atmosphere, continue unabated.
An overview of environment and development trends yields the following snapshot:
*. World population now at nearly 6 billion is growing more slowly than experts predicted just a few years ago but is still expected to increase substantially before stabilizing. Projections of future population, which are always highly uncertain, put world population at between 8 and 12billion in 2050, with nearly all of this growth expected in the developing world. An increasing number of the world’s people are receiving some degree of education, a factor closely tied to human well-being. During the past 30 years, a higher proportion of children have been attending school, and adult literacy has climbed.
*. The economic fortunes of a number of developing nations have risen steadily in the past two decades (although the recent downturn in Asian economies shows this growth may be fragile), but many other nations have experienced economic decline and falling per capita incomes since 1980. The disparity in incomes between the rich and poor within nations and between wealthy and poorer nations in general continues to widen, meaning that a relatively small percentage of the world’s people and nations control most of the world’s economic and natural resources.
*. Global food production is generally adequate to meet human nutritional needs, but problems with distribution mean that some 800 million people remain undernourished. World food production is still rising, but several trends will make it more challenging to feed an additional 3 billion people over the next 30 years. Yields of the major grain crops are rising more slowly now than in the past, and postharvest losses remain high. Soil degradation from erosion and poor irrigation practices continues to harm agricultural lands, jeopardizing production in some regions. In general, without a transition to more resource-efficient and less toxic farming methods, itwill be difficult to meet world food needs in the future without increasing agriculture’s environmental burden.
*. Consumption of natural resources by modern industrial economies remains very high—in the range of 45 to 85 metric tons per person annually when all materials (including soil erosion, mining wastes, and other ancillary materials) are counted. It currently requires about 300 kilograms of natural resources to generate US$100 of income in the world’s most advanced economies. Given the size of these economies, this volume of materials represents a truly massive scale of environmental alteration. For this reason, extending this kind of resource-intensive economic model to developing nations as is now occurring around the world is not environmentally viable.
*. Global energy use, which has increased nearly 70 percent since 1971, isprojected to increase at more than 2 percent annually for the next 15 years. This increase will bring more energy services such as refrigeration and transportation to people but will raise greenhouse gas emissions about 50 percent higher than current levels, unless a concerted effort takes place to increase energy efficiency and move away from today’s heavy reliance on fossil fuels. The low price and familiarity of fossil fuels work against the switch to renewable energy sources, such as wind, solar, geothermal, hydro, and others, but these clean energy sources are nonetheless undergoing considerable expansion and technical progress.
*. Nations have cut consumption of ozone-depleting substances some 70 percent since 1987, demonstrating that they can work together to address an environmental crisis, such as the depletion of the stratospheric ozone layer. However, the ozone layer is still not safe. Phaseout of chlorofluorocarbons (CFCs) and other ozone-destroying chemicals is not complete, and a significant black market in illegal CFCs has sprung up, endangering some of the gains already made.
*. In the past 50 years, excess nitrogen, principally from fertilizers, human sewage, and the burning of fossil fuels, has begun to overwhelm the global nitrogen cycle, with a range of ill effects ranging from reduced soil fertility to eutrophication in lakes, rivers, and coastalestuaries. The amount of biologically available (“fixed”) nitrogen may double over the next 25 years, increasing the current excess.
*. Acid rain is a growing problem in Asia, with sulfur dioxide emissions expected to triple there by 2010 if current trends continue.
*. Deforestation continues to shrink and degrade world forests, with deforestation rates in most countries surveyed increasing from 1990 to 1995 despite a surge of public awareness about the loss of forests, especially in the tropics. Deforestation in the Amazon doubled from 1994 to 1995 before declining in 1996, and forest fires in both Indonesia and the Amazon took a heavy toll in 1997. The world has lost half its forests over the past 8,000 years through conversion to farms, pastures, and human settlements or commercial sites.
*. Competition from nonnative plant and animal species “bioinvasions” represents a relentless and growing threat to natural ecosystems, with some 20 percent of the world’s endangered vertebrate species threatened by exotic invaders. Burgeoning world trade is one of the prime agents in the increasing pace of bioinvasions, which are now considered the second greatest threat to global biodiversity after habitat loss.
*. Risks to the world’s ecosystems are nowhere greater than in aquatic environments such as coral reefs and freshwater habitats in rivers, lakes, and wetlands. These fragile zones face an array of assaults from dams to land-based pollution to destructive fishing techniques. Some 58 percent of the world’s reefs and 34 percent of all fish species may be at risk from human activities.
*. Global water consumption is rising quickly, and water availability is likely to become one of the most pressing and contentious resource issues of the 21st Century. One third of the world’s population lives in countries already experiencing moderate to high water stress, and that number could rise to two thirds in the next 30 years without serious water conservation measures and coordinated watershed planning among water users.
What do these trends portend for the global environment? On the surface, they paint a troubling picture of the future, with many critical environmental indicators continuing to decline at their current pace or at increasing speed. Although global food supply and economic growth appear robust in the short term, such accumulating environmental harmultimately puts at risk the ecosystems and environmental processes such as climate that form the basis of human health and well-being. Yet, interpreting environmental trends requires care. Environmental threats are not always comparable or additive, since they differ greatly in termsof scale, effect, and the time frame in which they act, from the local and immediate threats of overfishing or deforestation, to long-acting and global-scale threats such as climate change.
Overall, the trends sketched above and detailed in the following pages support some important conclusions. First, changes to natural ecosystems are occurring on a larger scale than ever before, involving entire landscapes. Such large-scale landscape changes—through deforestation, expansion of agricultural land, and urban and suburban growth—will likely dictate the physical condition and extent of terrestrial ecosystems in the next several decades. Progressive fragmentation of the world’s remaining forest blocks; buildup in coastal areas; and the spread of cities, suburbs, and attendant roads and infrastructure over once-rural tracts will do much to degrade the habitatand watershed values of these areas. The map showing the current extent of “domesticated” land (see Chapter 5) indicates the extent to which these landscape-level changes have already altered the Earth’s surface.
Second, the very scale of these landscape-level changes, as well as the increasing intensity of industrial and agricultural processes, are inducingchanges in the global systems and cycles—such as the atmosphere and the nitrogen cycle—that underpin the functioning of ecosystems. These changes in what can be called the “global commons” represent long-term environmental threats of a profound and far-reaching nature. Global warming from the buildup of greenhouse gases is the best-knownexample, with the potential for large-scale disruption of natural ecosystems, agriculture, and human settlements due to changes in rainfall and temperature patterns and rising sea levels. Disruption of the global nitrogen cycle through extensive use of fertilizers, the burning of fossil fuels, and other activities also has the potential to change the structure and composition of terrestrial and aquatic ecosystems.
Third, threats to biodiversity from all sources are quickly reaching a critical level that may precipitate widespread changes in the number and distribution of species, as well as the functioning of ecosystems. Current extinction rates are 100 to 1,000 times higher than prehuman levels, and projected losses of habitat from land conversion, as well as increasing competition from nonnative species, will probably push this rate higher still.
Even as these trends indicate the environmental challenges ahead, it is important to remember that they can be modified with human resolve. Already, the transition to more environmentally benign ways of growingfood, producing goods and services, managing watersheds, and accommodating urban growth has begun in many far-sighted communities and companies. How fast this transition to more “sustainable” forms of production and environmental management will proceed, and whether it can effectively mitigate the effects of large-scale environmental change, is the real question..