If the nation could make New Year's resolutions, what would they be? Many possibilities come to mind, but one of the most pressing challenges that the United States - and indeed, the world - will face in the next few decades is how to alleviate the growing stress that human activities are placing on the environment. The consequences are just too great to ignore. Wildlife habitats are being degraded or are disappearing altogether as new developments take up more land. Plant and animal species are becoming extinct at a greater rate now than at any time in the Earth's history. As many as 30 percent of the world's fish stocks are overexploited. And the list goes on.

Yet there is reason to have hope for the future. Advances in computing power and molecular biology are among the tremendous increases in scientific capability that are helping researchers gain a better understanding of these problems. And scientific studies strongly suggest that measures such as establishing marine reserves and protecting endangered species are making a difference.

Much more could be accomplished. Recent developments in science and technology could provide the basis for some major and timely actions that would improve our understanding of how human activities affect the environment. I recently chaired a National Research Council committee that identified eight environmental science challenges with enormous potential for long-term benefit in the next decade. By focusing on these areas - think of them as New Year's resolutions for the environmental sciences - the U.S. government will ensure that precious research dollars are spent in areas that could make a real difference in addressing the most pressing problems of the relationship between humans and the environment. All the challenges are important and deserve strong support; four warrant immediate investment.

One is the study of biodiversity and ecosystem functioning. An improved understanding is needed of all of the factors - including human activities - that affect species diversity, and how that diversity relates to the overall functioning of an ecosystem. It is increasingly clear that humans and nature must exist side by side - in habitats that benefit all species. We do not yet know how to design such systems very well, and it is important that we find out.

Another immediate priority is improving hydrological forecasting. It has been estimated that the world's water use could triple in the next two decades. Already, widespread water shortages have occurred in parts of China, India, North Africa, and the Arabian peninsula. The need for water also is taking its toll on freshwater ecosystems in the United States. Only 2 percent of the nation's streams are considered in good condition, and close to 40 percent of native fish species are rare to extinct. Using a variety of new remote-sensing tools, scientists can learn more about how precipitation affects water levels, how surface water is generated and transported, and how changes in the landscape affect water supplies.

To prevent outbreaks of infectious diseases in plants, animals, and humans, more study is needed on how pathogens, parasites, and disease-carrying species - as well as humans and other species they infect - are affected by changes in the environment. The overuse of antibiotics both in humans and in farm animals has contributed to the growth of antibiotic-resistant microorganisms. Researchers can take advantage of new technologies in genetics and computing to better monitor and predict the effects that environmental changes might have on disease outbreaks.

Humans have made alterations to the Earth's surface - such as tropical deforestation, reduction of surface and ground water, and massive development - so dramatic that they approach the levels of transformation that occurred during glacial periods. Such alterations cause changes in local and regional climate, and will determine the future of agriculture. Recent advances in data collection and analysis should be used to document and better understand the causes and consequences of changes in land cover and use.

This knowledge won't come cheaply. Our committee roughly estimated that studying each of these areas will require several hundred million dollars - at a minimum - over a decade, for a total of perhaps $1 billion to $2 billion. This is, however, well within the $1 billion per year budget increase the National Science Foundation recommended for environmental sciences over the next five years. The wealth of information that would result will greatly outweigh the initial investments, and put us on track to a more sustainable future.