Annual Review of Environment and Resources - Volume 28, 2003

Variability of the atmospheric and oceanic circulations in the earth system gives rise to an array of naturally occurring dynamical modes. Instead of being spatially independent or spatially uniform, climate variability in different parts of the globe is orchestrated by one or a combination of several climate modes, and global changes take place with a distinctive spatial pattern resembling that of the modes-related climate anomalies. Climate impact on the dynamics of terrestrial and marine biosphere also demonstrates clear signals for the mode effects. In this review, we view modes as an important attribute of climate variability, changes, and impact and emphasize the emerging concept that future climate changes may be manifest as changes in the leading modes of the climate system. The focus of this review is on three of the leading modes: the North Atlantic Oscillation, the El Niño-Southern Oscillation, and the Pacific Decadal Oscillation.

The atmosphere is a chemically complex and dynamic system that interacts significantly with the land, oceans, and ecosystems. Most trace gases emitted into the atmosphere are removed by oxidizing chemical reactions involving ozone and the hydroxyl free radical. The rate of this self-cleansing process is often referred to as the oxidation capacity of the atmosphere. Without this process, atmospheric composition and climate would be very different from what we observe today. The fundamental chemistry involved and the influence of human activity on oxidation capacity are reviewed. Both the current measurements designed to determine rates of oxidation and evidence for changes in oxidizing capacity over recent decades are critically discussed.

This review evaluates analyses that are or may be performed to estimate uncertainties associated with air quality modeling used in regulatory planning to meet National Ambient Air Quality Standards for ozone. The sources of uncertainties in photochemical air quality simulation models (PAQSMs) are described. Regulatory requirements for evaluating PAQSM performance and uncertainty concerns not addressed through standard performance evaluations are discussed. Available techniques for evaluating uncertainties are presented. Experiences with analyses conducted most commonly are reviewed, as are those that might be used in a cohesive model uncertainty evaluation. The review concludes with a call for renewed emphasis on applying current techniques complemented by heretofore sparsely used diagnostic, corroborative, and alternative approaches and enhanced observational databases.

A variety of transport processes operate within the biosphere at all temporal and spatial scales. Temporary events or chronic conditions, both scale-dependent, instigate the transport of entities having material, energetic, or informational properties via several different transport vectors. The fluxes and influences imparted by these transport phenomena shape the physical environment, underlie gene flow, facilitate animal communication, and constrain the nature of local systems. These transport phenomena have been highly altered in the last century as humankind has become an ever more potent force in the earth system. As a result, issues of environmental and earth system science are, to a considerable extent, aspects of transport phenomena. A general appreciation for transport phenomena, broadly defined, is vital to gaining an appropriate perspective on the fluid nature of the earth system and to defining system structure and function through present and past events.

Biodiversity, a central component of Earth's life support systems, is directly relevant to human societies. We examine the dimensions and nature of the Earth's terrestrial biodiversity and review the scientific facts concerning the rate of loss of biodiversity and the drivers of this loss. The estimate for the total number of species of eukaryotic organisms possible lies in the 5–15 million range, with a best guess of ∼7 million. Species diversity is unevenly distributed; the highest concentrations are in tropical ecosystems. Endemisms are concentrated in a few hotspots, which are in turn seriously threatened by habitat destruction—the most prominent driver of biodiversity loss. For the past 300 years, recorded extinctions for a few groups of organisms reveal rates of extinction at least several hundred times the rate expected on the basis of the geological record. The loss of biodiversity is the only truly irreversible global environmental change the Earth faces today.

Forests are an important source for fiber and fuel for humans and contain the majority of the total terrestrial carbon (C). The amount of C stored in the vegetation and soil are strongly influenced by environmental constraints on annual C uptake and decomposition and time since disturbance. Increasing concentrations of atmospheric carbon dioxide (CO2), nitrogen deposition, and climate warming induced by greater greenhouse gas (GHG) concentrations in the atmosphere influence C accumulation rates of forests, but their effects will likely differ in direction and magnitude among forest ecosystems. The net interactive effect of global change on the forest C cycle is poorly understood. The growing demand for wood fiber and fuel by humans and the ongoing anthropogenic perturbations of the climate have changed the natural disturbance regimes (i.e., frequency and intensity); these changes influence the net exchange of CO2 between forests and the atmosphere. To date, the role of forest products in the global C cycle have largely been ignored, and important emissions associated with the production, transport, and utilization of the forest products have been excluded, leading to erroneous conclusions about net C storage in forest products.

We highlight the complexity of land-use/cover change and propose a framework for a more general understanding of the issue, with emphasis on tropical regions. The review summarizes recent estimates on changes in cropland, agricultural intensification, tropical deforestation, pasture expansion, and urbanization and identifies the still unmeasured land-cover changes. Climate-driven land-cover modifications interact with land-use changes. Land-use change is driven by synergetic factor combinations of resource scarcity leading to an increase in the pressure of production on resources, changing opportunities created by markets, outside policy intervention, loss of adaptive capacity, and changes in social organization and attitudes. The changes in ecosystem goods and services that result from land-use change feed back on the drivers of land-use change. A restricted set of dominant pathways of land-use change is identified. Land-use change can be understood using the concepts of complex adaptive systems and transitions. Integrated, place-based research on land-use/land-cover change requires a combination of the agent-based systems and narrative perspectives of understanding. We argue in this paper that a systematic analysis of local-scale land-use change studies, conducted over a range of timescales, helps to uncover general principles that provide an explanation and prediction of new land-use changes.

As increasing proportions of the world's population, production, and consumption become concentrated in urban areas, the need for urban development patterns that are more ecologically sustainable becomes obvious. A large proportion of the world's urban population also has needs that are unmet. We review the scale and nature of urban change worldwide, the environmental impacts of these changes, and the potentials and the difficulties in better meeting sustainable development goals in urban centers. The discussion of the interaction between city-based production and consumption and the resources and sinks on which these rely that are outside city boundaries is a reminder that the goal is not sustainable cities but cities that contribute to sustainable development within their boundaries, in the region around them, and globally.

Water managers and planners are slowly beginning to change their perspective and perceptions about how best to meet human needs for water; they are shifting from a focus on building supply infrastructure to improving their understanding of how water is used and how those uses can best be met. This review discusses definitions of water use, explores the history of water use around the world and in characteristic regions, identifies problems with collecting and analyzing water data, and addresses the question of improving water-use efficiency and productivity in different regions and economic sectors. There is growing interest on the part of water managers around the world to implement these approaches to lessen pressures on increasingly scarce water resources, reduce the adverse ecological effects of human withdrawals of water, and improve long-term sustainable water use.

Agriculture is a resource-intensive enterprise. The manner in which food production systems utilize resources has a large influence on environmental quality. To evaluate prospects for conserving natural resources while meeting increased demand for cereals, we interpret recent trends and future trajectories in crop yields, land and nitrogen fertilizer use, carbon sequestration, and greenhouse gas emissions to identify key issues and challenges. Based on this assessment, we conclude that avoiding expansion of cultivation into natural ecosystems, increased nitrogen use efficiency, and improved soil quality are pivotal components of a sustainable agriculture that meets human needs and protects natural resources. To achieve this outcome will depend on raising the yield potential and closing existing yield gaps of the major cereal crops to avoid yield stagnation in some of the world's most productive systems. Recent trends suggest, however, that increasing crop yield potential is a formidable scientific challenge that has proven to be an elusive goal.

The total world catch from marine and freshwater wild stocks has peaked and may be slightly declining. There appear to be few significant resources to be developed, and the majority of the world's fish stocks are intensively exploited. Many marine ecosystems have been profoundly changed by fishing and other human activities. Although most of the world's major fisheries continue to produce substantial sustainable yield, a number have been severely overfished, and many more stocks appear to be heading toward depletion. The world's fisheries continue to be heavily subsidized, which encourages overfishing and provides society with a small fraction of the potential economic benefits. In most of the world's fisheries there is a “race for fish” in which boats compete to catch the fish before a quota is achieved or the fish are caught by someone else. The race for fish leads to economic inefficiency, poor quality product, and pressure to extract every fish for short-term gain. A number of countries have instituted alternative management practices that eliminate the race for fish and encourage economic efficiency, use lower exploitation rates that deliberately do not attempt to maximize biological yield, and encourage reduced fishing costs and increased value of products. In fisheries where this transition has taken place, we see the potential for future sustainability, but in those fisheries where the race for fish continues, we anticipate further declines in abundance, further loss of jobs and fishing communities, and potential structural change to marine ecosystems.

Green chemistry and engineering is the design of chemical manufacturing systems to minimize their adverse affects on the environment. Thus, a primary goal of green chemistry and engineering is to reduce the environmental impact of chemical processes and chemical manufacturing while simultaneously enhancing the overall process performance. Although it is beneficial to simply reduce the use of organic solvents in chemical processes, green chemistry and engineering goes further, in that it evaluates the entire manufacturing operation to identify techniques that can be applied to minimize the overall process hazard, while maintaining economic practicality. Evaluation of the environmental impacts of the manufacturing process requires a systems approach and appropriate metrics that permit quantitative assessment of environmental hazards. Thus, this chapter begins with a discussion of the drivers for green engineering and the metrics through which processes can be evaluated. Then, the hydroformylation process is used as a case study to illustrate the way in which green chemistry principles can be applied to real processes. Two elements are specifically highlighted: (a) the use of catalysts to facilitate active and selective chemistry and the immobilization of said catalysts within the reactor system, and (b) the development of processes based on benign reaction solvents, and the benefits that can accrue from simplified separations operations.

International environmental agreements (IEAs), legally binding intergovernmental efforts directed at reducing human impacts on the environment, are common features of global environmental governance. Using a clear definition allowed creation of a comprehensive database [available online at (31)] listing over 700 multilateral agreements (MEAs) and over 1000 bilateral agreements (BEAs), which included treaties, protocols, and amendments that address numerous pollutants; preservation of many species; and, increasingly, protection of various habitats. Research into the factors that explain the timing, content, and membership in environmental agreements clarifies that the interests and power of influential states create pressures for, or constraints on, progress in global environmental governance but that discourse, actors, and processes also play important roles. Variation in the effects of these agreements on environmental behaviors and outcomes often depends as much on characteristics of member countries, the international context, and the underlying environmental problem as on the differences in agreement design.

Widespread observations of organic pollutant compounds in vegetation, soil, animals, and human tissue have motivated research on more accurate characterizations of chemical transport over regional, continental, and global scales. Efforts to assess human and ecosystem exposure to contaminants from multiple environmental media have been evolving over the last several decades. In this review, we summarize the development and evolution of the multimedia mass-balance approach to pollutant fate and exposure evaluation and illustrate some of the calculations used in multimedia assessments. The concepts that form the foundation of Mackay-type mass-balance compartment models are described, and the ongoing efforts to use multimedia models to quantify human exposures are discussed. A series of case studies of varying complexity are used to illustrate capabilities and limitations of selected multimedia approaches. We look to the future and consider current challenges and opportunities in the field of multimedia contaminant fate and exposure modeling.

The geographic context is essential both for environmental research and for policy-oriented environmental management. Geographic information systems are as a result increasingly important computing applications in this domain, and an understanding of the underlying principles of geographic information science is increasingly essential to sound scientific practice. The review begins by defining terms. Four major sections follow that discuss advances in GIS analysis and modeling, in the supply of geographic data for GIS, in software design, and in GIS representation. GIS-based modeling is constrained in part by architecture, but a number of recent products show promise, and GIS continues to support modeling through the coupling of software. The GIS data supply has benefited from a range of new satellite-based sensors and from developments in ground-based sensor networks. GIS software design is being revolutionized by two developments in the information technology mainstream: the trend to component-based software and object-oriented data modeling. Advances in GIS representation focus largely on time, the third spatial dimension, and uncertainty. References are provided to the more important and recent literature. The concluding section identifies three significant and current trends: toward increasing interoperability of data and services, increasing mobility of information technology, and increasing capabilities for dynamic simulation.

Agriculture and industrial development have led to inadvertent changes in the natural carbon cycle. As a consequence, concentrations of carbon dioxide and other greenhouse gases have increased in the atmosphere and may lead to changes in climate. The current challenge facing society is to develop options for future management of the carbon cycle. A variety of approaches has been suggested: direct reduction of emissions, deliberate manipulation of the natural carbon cycle to enhance sequestration, and capture and isolation of carbon from fossil fuel use. Policy development to date has laid out some of the general principles to which carbon management should adhere. These are summarized as: how much carbon is stored, by what means, and for how long. To successfully manage carbon for climate purposes requires increased understanding of carbon cycle dynamics and improvement in the scientific capabilities available for measurement as well as for policy needs. The specific needs for scientific information to underpin carbon cycle management decisions are not yet broadly known. A stronger dialogue between decision makers and scientists must be developed to foster improved application of scientific knowledge to decisions. This review focuses on the current knowledge of the carbon cycle, carbon measurement capabilities (with an emphasis on the continental scale) and the relevance of carbon cycle science to carbon sequestration goals.

Sustainable development has broad appeal and little specificity, but some combination of development and environment as well as equity is found in many attempts to describe it. However, proponents of sustainable development differ in their emphases on what is to be sustained, what is to be developed, how to link environment and development, and for how long a time. Despite the persistent definitional ambiguities associated with sustainable development, much work (over 500 efforts) has been devoted to developing quantitative indicators of sustainable development. The emphasis on sustainability indicators has multiple motivations that include decision making and management, advocacy, participation and consensus building, and research and analysis. We select a dozen prominent examples and use this review to highlight their similarities and differences in definition of sustainable development, motivation, process, and technical methods. We conclude that there are no indicator sets that are universally accepted, backed by compelling theory, rigorous data collection and analysis, and influential in policy. This is due to the ambiguity of sustainable development, the plurality of purpose in characterizing and measuring sustainable development, and the confusion of terminology, data, and methods of measurement. A major step in reducing such confusion would be the acceptance of distinctions in terminology, data, and methods. Toward this end, we propose an analytical framework that clearly distinguishes among goals, indicators, targets, trends, driving forces, and policy responses. We also highlight the need for continued research on scale, aggregation, critical limits, and thresholds.

This review presents existing data and research on the global distribution of the impacts of oil production and consumption. The review describes and analyzes the environmental, social, and health impacts of oil extraction, transport, refining, and consumption, with a particular focus on the distribution of these burdens among socioeconomic and ethnic groups, communities, countries, and ecosystems. An environmental justice framework is used to analyze the processes influencing the distribution of harmful effects from oil production and use. A critical evaluation of current research and recommendations for future data collection and analysis on the distributional and procedural impacts of oil production and consumption conclude the review.