APPENDIX D
Extended Speaker Abstracts1

ADDRESSING MULTIPLE STRESSES

Eric J. Barron

The University of Texas at Austin


The nature of the environmental issues facing any nation demands a capability that allows us to enhance economic vitality, maintain environmental quality, limit threats to life and property, and strengthen fundamental understanding of the earth. In each case it is the ability to anticipate the future (e.g., a forecast of an impending storm, a prediction of the water quality change in response to a new source of pollutant) that makes information about the earth system truly useful. Reliable information about the future (i.e., predictions) is the key to addressing environmental issues. However, society requires greater access to and greater confidence in both information and forecasts or projections in order to weigh the advantages and risks of alternative courses of action by private and public decision makers. Such information is a key commodity in enhancing economic vitality and societal well-being. What stands in our way of providing this information?

THE NATURE OF THE PROBLEM

The driving forces that alter environmental quality and integrity are widely recognized, involving primarily weather and climate, patterns of land use and

1

Presented in the order given during the workshop.



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Understanding Multiple Environmental Stresses: Report of a Workshop APPENDIX D Extended Speaker Abstracts1 ADDRESSING MULTIPLE STRESSES Eric J. Barron The University of Texas at Austin The nature of the environmental issues facing any nation demands a capability that allows us to enhance economic vitality, maintain environmental quality, limit threats to life and property, and strengthen fundamental understanding of the earth. In each case it is the ability to anticipate the future (e.g., a forecast of an impending storm, a prediction of the water quality change in response to a new source of pollutant) that makes information about the earth system truly useful. Reliable information about the future (i.e., predictions) is the key to addressing environmental issues. However, society requires greater access to and greater confidence in both information and forecasts or projections in order to weigh the advantages and risks of alternative courses of action by private and public decision makers. Such information is a key commodity in enhancing economic vitality and societal well-being. What stands in our way of providing this information? THE NATURE OF THE PROBLEM The driving forces that alter environmental quality and integrity are widely recognized, involving primarily weather and climate, patterns of land use and 1 Presented in the order given during the workshop.

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Understanding Multiple Environmental Stresses: Report of a Workshop land cover, and resource use with its associated waste products. But a key feature of most regions is that more than one driving force is changing simultaneously. Consequently, most locations are characterized by multiple stresses. The effect of a combination of environmental stresses is seldom simply additive. Rather, they often produce amplified or damped responses, unexpected responses, or threshold responses in environmental systems. Multiple, cumulative, and interactive stresses are clearly the most difficult to understand and hence the most difficult to manage. In contrast, most research, analysis, and policy are based on studies that examine discrete parts of these complex problems. Basically, earth and environmental sciences tend to focus on cause and effect, where we seek to understand how a specific element of the system may respond to a specific change or perturbation (e.g., acid rain on lake fisheries). The lack of an ability to assess the response of the system to multiple stresses limits our ability to assess the impacts of specific human perturbations, to assess advantages and risks, and to enhance economic and societal well-being in the context of global, national, and regional stewardship. However, the problem is not limited simply to moving from analysis of discrete parts of complex problems to a more comprehensive analysis. First, economic vitality and societal well-being are increasingly dependent on combining global, regional, and local perspectives. A “place-based” imperative for environmental research stems from the importance of human activities on local and regional scales, the importance of multiple stresses on specific environments, and the nature of the spatial and temporal linkages between physical, biological, chemical, and human systems. We find the strongest intersection between human activity, environmental stresses, earth system interactions and human decision making in regional analysis coupled to larger spatial scales. Second, a decade of research on greenhouse gas emissions, ozone depletion, and deforestation has clarified many critical unanswered questions. However, the last decade of effort has also revealed a number of challenges, most notably the challenge of creating integrated global observational capabilities and the computational and scientific limitations inherent in creating a truly integrated, global, coupled system modeling capability suitable for assessing impacts and adaptations. These problems are noteworthy in global change science, but they become intractable at the scales of human decision making. A major part of the problem is simply a matter of scale combined with the sheer information required to combine physical, biological, chemical, and human systems if the framework is global. For example, whereas a global integrated observing system is challenging but tractable and plays a fundamental role on the scale of a global circulation model, it collapses under its own weight at higher spatial resolutions if we demand a truly comprehensive data system involving the host of observations spanning biology, hydrology, soils, weather, etc., required to address problems at

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Understanding Multiple Environmental Stresses: Report of a Workshop the scales of human decision making. For this reason, we have never fully realized the objective of “earth system science.” Recognition of the importance of developing a more integrated approach to environmental research was abundantly clear in the U.S. National Assessment of Climate Change Impacts on the United States (NAST, 2000). The first recommendation for future research focused on developing a more integrated approach to examining impacts and vulnerabilities to multiple stresses. There were many examples in which the key limitation to the assessment of potential impacts to climate change was a lack of knowledge of other stressors. For example, changes in insect-, tick-, and rodent-borne diseases could be clearly tied to weather and climate, but a number of other environmental factors that could influence the disease vectors (e.g., the importance of land cover/land use on disease hosts), transmission dynamics, and population vulnerabilities severely limited our ability to make robust conclusions on how climate change might influence the distribution and occurrence of many infectious diseases in the future. ADDRESSING SOCIETAL NEEDS The need for society to enhance economic vitality, while maintaining environmental quality and limiting threats to property and life, should drive the environmental research and operational enterprise. These societal needs lead to a vision that requires a focus on multiple stresses. To address this vision, we need to develop a comprehensive regional framework for environmental science. This vision includes five elements: an integrated regional web of sensors, including physical, chemical, biological, and socioeconomic factors, that link existing observations into a coherent framework and enable new observations to be developed within an overall structure; an integrated and comprehensive regional information system, accessible to a wide variety of researchers, operational systems, and stakeholders; directed process studies designed to examine specific phenomena through field study to address deficiencies in understanding; a regional, high-resolution modeling foundation for constructing increasingly complex coupled system models at the spatial and temporal scales appropriate for the examination of specific and integrated biological, hydrological, and socioeconomic systems; and a strong connection to significant regional issues and stakeholders. These five elements are described in detail below: 1. A Web of Integrated Sensors. The current U.S. observation strategy appears to be haphazard when viewed in the overall context of environmental

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Understanding Multiple Environmental Stresses: Report of a Workshop problems. The reason is clear. The observations are driven by different mission needs and tend to focus on the measurement of discrete variables at a specific set of locations designed to serve the different needs of weather forecasting, pollution monitoring, hydrological forecasting, or other objectives. The mission focus results in a diverse set of networks that are supported by a large number of different federal agencies, states, or regional governments. Increased awareness of a host of environmental issues drives demand for additional new observations. However, these new observations are frequently viewed independently of any overall structure or integrated observing strategy. Operational needs and research or long-term monitoring needs are also often independent. Importantly, regular and consistently repeated observations present added challenges in garnering sufficient financial resources. The end result is almost certainly fiscally inefficient, and undoubtedly limits our ability to integrate physical, biological, chemical, and human systems. The limitations of the current observing strategy are widely recognized, and they have spurred efforts to develop global observing systems for global change, climate, and oceanic and terrestrial systems in the international arena. These efforts are commendable and must be encouraged, but they are also extremely challenging because of the breadth of measurements, nations, capabilities, and policies that are involved. In contrast, at a regional level in the United States we have the potential to (a) link observing systems into a web of integrated sensors building upon existing weather and hydrological stations and remote sensing capability; (b) create the agreements across a set of more limited agencies and federal, state, and local governments needed to create a structure to the observing system; (c) provide a compelling framework that encourages or demands the integration of new observations into a broader strategy; and (d) create strong linkages between research and operational observations that result in mutual benefit. The result is likely to create new efficiencies through the development of measurement systems that are more comprehensive, rather than a suite of separately funded, disconnected systems. The result is also likely to result in greater scientific benefit to society and greater understanding due to the co-location or networking of many different measurement capabilities. The demonstration of fiscal efficiency and improved capability and resulting benefit are likely to create a significant additional impetus for developing national and global integrated observing systems. 2. Regional Information Systems. Society has amassed an enormous amount of data about the earth. New satellite systems and other observational capabilities promise enormous increases in the availability of earth data. Fortunately, technological innovations are allowing us to capture, process, and display this information in a manner that is multiresolution and four-dimensional. The major challenges involve data management; the storage, indexing, referencing, and retrieving of data; and the ability to combine, dissect, and query information. The

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Understanding Multiple Environmental Stresses: Report of a Workshop ability to navigate this information, seeking data that satisfy the direct needs of a variety of users, is likely to spark a new “age of information” that will promote economic benefit and engender new research directions and capabilities to integrate physical, biological, chemical, and human systems. The efforts to create comprehensive information systems increasingly reflect federal and state mandates to make data more accessible and useful to the public and to ensure that our investments in research yield maximum societal benefit. The development of a global digital database is again an enormous challenge. In contrast, a regional or state focus becomes a logical test bed, enabling the participation of universities; federal, state, and local governments; and industry in the development of a regional information system that is tractable and for which immediate benefit for a state or region can be evident. Again, the demonstration of capability and resulting benefit are likely to create a significant additional impetus for developing national and global information systems. 3. Framework for Process Studies. Process studies are a critical element of scientific advancement because they are designed, through focused observations and modeling, to probe uncertainties in knowledge about how the earth system functions. In many cases mismatch between model predictions and observations can drive targeted investigations to limit the level of error. Frequently, efforts to couple different aspects of the earth system (e.g., the atmosphere and land-surface vegetation characteristics) prompt targeted exploration because the level of understanding is still rudimentary. The objective is to use field study to address deficiencies in our understanding. The benefit of these intensive studies is maximized when they can be coupled with a highly developed, integrated set of sensors, with readily accessible spatial and temporal data within a regional information system, and with a predictive model framework that readily enables the entrainment and testing of new information from process studies. Hence, a regional focus is empowered by process studies that are directly tied to answering specific questions designed to assess the impacts of specific human perturbations, to assess advantages and risks, and to enhance economic and societal well-being. 4. Predictive Capability. The value of reliable advanced information is widely recognized. For example, we have considerable experience with the benefit of reliable weather forecasts, whether it involves the planning of a day around a precipitation forecast, the protection of life and property that stems from severe weather warnings, or the economic benefit of weekly, seasonal, or interannual forecasts used by climate- or weather-sensitive industries such as agriculture, forestry, fisheries, construction, or transportation. For example, millions of dollars in commodity markets can be saved by regional utilities with advanced weather or seasonal forecasts, and El Niño forecasts a season in advance can substantially modify agricultural practice.

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Understanding Multiple Environmental Stresses: Report of a Workshop Prediction is central to the translation of knowledge about the earth system into economic benefit and societal well-being. Over the last several decades we have experienced enormous increases in our ability to forecast weather and to project climate and climate variability into the future. The demand for new forecasting products, involving air quality, energy demand, water quality and quantity, ultraviolet radiation, and human health indexes is also growing rapidly, and as we demonstrate feasibility and benefit, society is likely to demand a growing number of new operational forecast products on prediction timescales of days to decades into the future. Further, we already clearly sense that environmental issues will demand an even greater capability to integrate physical, biological, chemical, and human systems in order to develop the predictive capability needed to examine the response of critical regions or cases to multiple stresses. Global weather and climate models provide the strongest physical foundation for more comprehensive predictive capability. The numerical models that underpin this type of forecast are increasingly becoming the framework for the addition of new numerical formulations designed to predict air quality, the water balance for river forecast models, and a host of other variables, including the migration of forests under climate change conditions. As we attempt to produce predictions at the scale of human endeavors, mesoscale models (capable of predicting synoptic weather systems) and downscaling of coarser resolution model output are increasingly becoming the focal point of weather and climate studies because of their potential to make predictions on the scale of river systems, cities, agriculture, and forestry. Enormous potential exists if we can institutionalize a mesoscale numerical prediction capability that meshes with regional sensor webs and information systems. Such a capability enables a strategy and implementation capability for building tractable coupled models, initiating experimental forecasts of new variables, assessing the outcomes associated with multiple stresses, and taking advantage of the discipline of the forecasting process to create a powerful regional prediction capability. This capability, built upon the numerical framework of weather and climate models, can be extended to air quality, water quantity and quality, ecosystem health, human health, agriculture, and a host of other areas. It is time to bring a demanding level of discipline to the forecasting of a wide variety of environmental variables. The objective is to stimulate the interplay between improvements in observation, theory, and practice needed to develop capabilities of broad value to society. The discipline of forecasting is dependent on four steps: (1) collection and analysis of observations of present conditions; (2) use of subjective or quantitative methods to infer future conditions; (3) assessment of the accuracy of the prediction with observations; and (4) analysis of the results to determine how methods and models can be improved. At a minimum we are capable of bringing a much greater level of structure and discipline into our predictions of the future, ranging from specific forecasts to statistical ensembles

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Understanding Multiple Environmental Stresses: Report of a Workshop that include a measure of expected accuracy to an assessment of the range of possibilities. 5. Creation of a Vigorous and Continuous Link to Users and Decision Makers. We need to create a vigorous connection between the research and decision makers by (a) incorporating the variety of space and timescales and the diversity of variables that are important to decision makers; (b) emphasizing the education of the user in the meaning and significance of climate and land use information in order to promote greater use and more robust applications; (c) ensuring mutual information exchange and feedback; (d) focusing on communication and accessibility of information; (e) continuously evaluating and assessing the use and effectiveness of the services; (f) employing active mechanisms to enable the transition from research discovery to useful products; and (g) employing a variety of methods of education and outreach. SUMMARY The above structure is inherently a hybrid between research and operational functions. Both benefit from the level of integration of observations and information, the targeted process studies, and the model development capability. An emphasis on a region-specific predictive capability will drive the development of new understanding and new suites of comprehensive interactive high-resolution models that focus on addressing societal needs. A key objective is to bring a demanding level of discipline to “forecasting” in a broad arena of environmental issues. Common objectives and an integrated framework will also engender new modes and avenues of research and catalyze the development of useful operational products. With demonstrated success, the concepts of integrated regional observation and information networks, combined with comprehensive models, will grow into a national capability that far exceeds current capabilities. Such a capability is designed to address a broad range of current and future regional and global environmental issues. Eric Barron is dean of the Jackson School of the University of Texas at Austin. Prior to assuming his current position he served as dean of the College of Earth and Mineral Sciences and Distinguished Professor of Geosciences at the Pennsylvania State University. His research interests are in the areas of climatology, numerical modeling, and earth history. Dr. Barron received his Ph.D. in oceanography from the University of Miami.

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Understanding Multiple Environmental Stresses: Report of a Workshop DROUGHT: OBSERVATIONS, MECHANISMS, POTENTIAL SURPRISES AND CHALLENGES Jonathan Overpeck University of Arizona INTRODUCTION Drought is one of the most challenging and costly environmental concerns confronting society. Over time, many institutions have been developed to deal with drought, but there is still a regular multi-billion dollar annual drought impact in the United States alone. Moreover, a complete consideration of drought provides a sobering view of the future. The purpose of this presentation is to provide an overview of drought variability and related issues. Drought is a concern worldwide, but by necessity this presentation will focus on North America only. Nonetheless, many of the North American lessons can inform climate-society debates elsewhere—particularly in Africa, where there is also a rich history of observations, as well as research on the causes and impacts of drought variability. THE INSTRUMENTAL RECORD OF DROUGHT Drought is always affecting some part of North America, and even a single-year drought has impact and is thus important. The longer droughts are of greater concern, with the droughts of the 1930s, 1950s, and 1999 to the present being the droughts of record and of most concern. These longer droughts all affected large portions of North America. The most recent drought is particularly notable in that it was hotter than the similar drought of the 1950s. In general, western North America has seen significant warming over the last 100 years, particularly in the last couple of decades. It is notable that the recent period of unprecedented population increase in the western United States coincided with one of the wettest periods on record. It is also troubling that Colorado River water was divided up among basin states during the one of the other wettest periods: in total, 16.5 MAF of water was allocated per year, even though the measured flow during the early 20th century wet period was less than 15 MAF per year. THE PALEOCLIMATIC RECORD OF DROUGHT Even a quick glance at the paleoclimate record of drought makes it clear that the instrumental record provides a biased record of drought due to a shortness of record. Droughts comparable to the 1930s, 1950s or early 2000s have occurred,

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Understanding Multiple Environmental Stresses: Report of a Workshop in general, once or twice per century over the last 2,000 years. The true long-term average flow of the Colorado is well below what is allocated to western states and Mexico. All droughts of the 20th century were eclipsed by past droughts, both in terms of annual maximum severity, duration, and geographic extent. It is clear from the paleoclimatic record that droughts longer than a decade (i.e., “mega-droughts”) were not that rare and that droughts impacting much of the western United States have lasted as long as a century or more within the last 2,000 years. Paleoclimatic research has shown that at least one lake in the Sierra Nevada of western North America went dry for decades on more than one occasion—something that has not occurred since Europeans settled the West. The true range of “natural” drought variability is thus substantially larger and more complex than suggested by the last century of instrumental drought variation. In general, most of the large droughts of the western United States have been large enough to affect more than one major river basin at a time, and some (e.g., the late 16th-century megadrought) apparently impacted the United States from coast to coast and from northern to southern borders. Many (all?) long-duration droughts moved spatially from year to year and usually included years with normal or above-normal rainfall. Another key aspect of drought variability illuminated by the paleoclimatic record is that decades- to centuries-long hydrological “regimes” (e.g., characterized by rare/short or frequent/longer droughts) have begun and ended abruptly— transitions between drought regimes can take place over years to decades, whereas the regimes themselves can be significantly longer. MECHANISMS OF DROUGHT VARIABILITY Great strides have been made recently with respect to understanding the proximal cause of drought in North America. We have long known that drought in the southwestern United States (e.g., 1950s and the recent drought) have connections with ENSO and that dry winters are favored in La Niña years. More recently, modeling studies have confirmed that anomalous sea surface temperature (SST) patterns, particularly in the tropics, and particularly in the Indo-Pacific, can explain both 20th-century and earlier droughts. Moreover, research has now also identified strong relationships between decadal modes of Pacific and Atlantic variability with decadal patterns of wet and dry conditions over North America. Of course, the major challenge is to explain the causes of the anomalous—and persistent—ocean conditions that lead to North American drought. Although land-surface feedbacks can play key roles in amplifying or damping drought, it appears that these feedbacks are not dominant in driving temporal drought variability. More work is needed on the role these feedbacks play, but only after recognizing that coupled atmosphere-ocean variability is likely more important.

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Understanding Multiple Environmental Stresses: Report of a Workshop POTENTIAL SURPRISES It is just a matter of time until North America gets hit with a decadal mega-drought. This is likely regardless of how large any anthropogenic impact might be. Thus warned, why would anyone be surprised? This shortcoming of human nature needs to be understood and overcome. ANTHROPOGENIC VERSUS NATURAL DROUGHT INFLUENCES The IPCC (TAR and a recent CLIVAR-PAGES-IPCC workshop convened by Overpeck and Trenberth) concluded that anthropogenic forcing will likely increase the probability of drought in central and western North America. Exacerbating this likelihood is the fact that temperatures are already rising significantly in the West, and snowpack is already retreating in the same region (as a result of the warming). A lesson of the paleoclimatic record is that anthropogenic forcing could trigger an abrupt transition into a more drought-prone climatic regime, thus increasing the frequency and duration of drought. Given that these possibilities could materialize with or without significant future human-induced climate change, it makes sense to consider no-regrets strategies to reduce vulnerability to drought in either case. Most recently it has been proposed that unprecedented warming in the tropical Indian and western Pacific Oceans—likely a result of global warming—is the cause of the ongoing western North American drought. This hypothesis is well supported by modeling studies and is troubling in that the anomalous warming could become the norm in the future in years without El Niño events. If dry conditions intensify this winter, it could be a sign that we are in what could turn out to be the first megadrought since Europeans settled North America. CHALLENGES AND OPPORTUNITIES Needless to say, there is a great deal of additional insight that could be revealed through a more comprehensive study of past drought and megadrought. Can we define the full range of possible drought sufficiently for successful no-regrets adaptation? What are the empirical links between drought and variability in sea surface temperatures? What sets up the anomalous SSTs? Are the anomalies forced or generated by internal variability in the coupled system? What are the potential triggers of abrupt hydrological change? Are there early warning signs to be monitored for? Can droughts and megadroughts be predicted? Are surprises avoidable? Although the mechanisms of drought cannot be understood fully without much improved observations (particularly paleo), the most important challenge might be in the area of ocean and coupled atmosphere-ocean modeling. Whereas the instrumental record of drought can be simulated fairly well given specified (observed) SST fields, the same drought record cannot be simulated with state-

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Understanding Multiple Environmental Stresses: Report of a Workshop of-the-art coupled models. Clearly, the development of more realistic coupled models must be an urgent priority. Dealing with drought requires the ability to understand regional climate variability over all seasons and to eventually be able to deliver reliable seasonal to interannual climate outlooks. At present, advances are limited by modeling regional-scale processes, and this limitation is in turn related by the lack of good regional-scale climate monitoring. Thus, there is an increased need for denser in situ climate observing in the topographically complex western epicenter for U.S. drought. BOTTOM LINE? Even if we develop an ability to predict drought, we must work with stakeholders in society (particularly in central and western North America) to develop adaptation strategies that reduce vulnerability to megadrought. There is little doubt that such a drought will occur at some time in the future and that anthropogenic climate change will exacerbate the situation. There is also little doubt that stakeholders and institutions are ill prepared for the inevitable megadrought. Jonathan Overpeck is both a professor and director of the Institute for the Study of Planet Earth at the University of Arizona. Dr. Overpeck’s research focuses on global and regional climate dynamics. His research aims to reconstruct and understand the full range of climate system variability, recognize and anticipate possible “surprise” behavior in the climate system, understand how the earth system responds to changes in climate forcing, and detect and attribute environmental change to various natural (e.g., volcanic, solar) and nonnatural (e.g., greenhouse gases or tropospheric aerosol) forcing mechanisms. His work also focuses on improving the use of climate knowledge by decision makers in society.

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Understanding Multiple Environmental Stresses: Report of a Workshop then cities from both the developed and the developing world may become vulnerable. Consider the 2003 heat wave in Europe as example of an event a developed country like France was vulnerable to. This did not necessarily result from lack of resources. But it rather related not only to health conditions and health services for the elderly people, but also to social conditions and organization (i.e., to inadequate climate conditioning in buildings; to the fact that the elderly people were alone while their families were on vacation). Think about environmental change’s possible impacts on the pool of resources and ecosystems an urban area relies on. As some scenarios foresee, climate change will strongly affect already stressed watersheds in both the developing world (e.g., Lerma and Cutzamala for Mexico City) and the developed world (Colorado River for Southern California). The problem is that most scholars tend to focus either on some drivers of emissions trajectories (e.g., IPCC’s Work Group III) or on the vulnerability or impact to multiple stresses (e.g., IPCC’s Work Group II using vulnerability assessments). And knowledge would advance faster if both groups could explore and model the complex linkages between drivers of development pathways and stressors facing urban sectors and localities. Consider another example. Market forces and the declining role of the state as urban planner are key drivers of urban growth in risk-prone areas of developing countries and even of industrialized countries—as New Orleans has recently shown us. The retrenchment of the state in its role as regulator usually appears as one of the multiple stresses facing urban dwellers. Wouldn’t it be better to explore how market forces and other drivers relate or cascade with other and multiple stresses to produce certain vulnerabilities/adaptive capacities? Isn’t it a challenge to develop an integrated perspective to understand the pathways through which socioeconomic, institutional, and environmental processes influence livelihoods, economic activities, urban life, migration, and other realms where adaptive capacity takes place in urban areas? RELEVANCE OF SCALE Scale is important in diverse and not yet fully explored ways when assessing the socioeconomic impacts of changes in atmospheric composition and dynamics. First, the referred changes are but a part of a set of multiple stresses operating at diverse scales in space and through time (e.g., markets, deficiencies in housing, or in the supply and operation of urban services, infrastructure, sanitation, and health). The problem is that research on this issue is in its infancy. We need to better understand—and if possible model—the global and regional socioeconomic, geopolitical, and environmental processes affecting the vulnerability of urban systems.

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Understanding Multiple Environmental Stresses: Report of a Workshop Second, both the exposure to and the distribution of urban groups and localities sensitive to the impacts of changes in atmospheric composition and dynamics vary greatly across scale. The primary social and economic conditions that influence adaptive capacity (e.g., access to financial resources or to governmental relief) also differ with scale. One could say, for instance, that at a national scale cities in industrialized countries such as Norway or the United States can cope with most kinds of gradual environmental changes, but focusing on more localized differences (between New York and New Orleans for instance) can show considerable variability in stresses and capacities to adapt. This is another area where more research is needed. Third, temporal scale is a critical determinant of the capacity of urban systems to adapt to environmental changes. The history of the city—path dependency—will determine the diversity and complexity of its population’s current and future adaptive capacity. Of course, rapid changes or abrupt changes (e.g., flooding, droughts) are more difficult to absorb without painful costs than gradual change. But gradual change can accumulate until urban areas reach a threshold in which their adaptive capacity is no longer feasible. Consider how slow changes in the length and frequency of seasons could affect water supplies in cities, or how slow changes in temperature and humidity could affect the livelihood of urban people. These issues have received little attention so far. ANALYTICAL TOOLS Rather than using one-dimensional perspectives to understand the responses of urban areas to the impacts of changes in the composition of the atmosphere, we need broader multidimensional and multiscale approaches. This is a challenge indeed. Examples of such tools and concepts that will be described in this section are the Kaya identity, vulnerability/adaptation assessments, livelihoods, and tolerable windows approach. According to the IPAT identity, environmental impact is the product of the level of population combined with affluence (e.g., measured by income per capita) and the level of technology (e.g., measured by emissions per unit of income). Numerous articles use this kind of identity to analyze the drivers of CO2 emissions (Kaneko and Matsouka, 2003), often referring to it as the “Kaya identity,” according to which:2 2 Note that some of the components can be analyzed for sectors of activity to get greater detail of emissions sources.

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Understanding Multiple Environmental Stresses: Report of a Workshop The Kaya identity has the advantage of being simple and allowing for “some standardization in the comparison” and analysis of diverse emissions trajectories (Nakicenovic, 2004). Clearly, it is a very general way of looking at emissions; for example, it assumes that each variable enters linearly and independently, which is surely not the case, and it omits other factors (such as institutional ones) as emissions drivers that are left as residual of the equation if looking at past emissions evolution (IPCC, 2000; Nakicenovic, 2004). The identity is broadly used to construct scenarios; it helps to identify proximate but not ultimate drivers, but it fails to identify many key drivers—e.g., government regulation, social organization, and economic organization, as well as public perceptions, which influence patterns of technologies in use affecting trajectories of greenhouse gases and other atmospheric releases.3 The question is whether a similar equation in which the variables do not enter independently could be applied to the analysis of multiple stresses, whether such an equation could at least allow for some standardization in the comparison of diverse cases. Rather than selecting a particular environmental stress of concern and trying to identify its consequences as impact assessment does, vulnerability/adaptation assessments: Choose a group or unit of concern (e.g., informal or wealthy settlements, poor or rich urban dwellers). Try to evaluate the risk of specific adverse outcomes for that unit when confronted with a set of stresses (e.g., climate variability and change, new patterns of foreign direct investment and of industrial location, and structural adjustment programs). Note that all these stresses redefine the economic base of urban areas, drive new territorial patterns of urban growth and new emissions trajectories (Romero Lankao et al., 2005); at the same time they define a new physiognomy and geography of vulnerable groups and localities within the cities. Seek to identify a set of factors (e.g., institutions, assets, social capital) that may reduce or to the contrary enhance adaptation to those stressors. Precisely because vulnerability assessments concentrate on exposure units, they assume that vulnerability is highly dependent on scale and context. This has two consequences we should address in our workshop. Assessments focusing on a narrow range of scales will miss most of the importance for societal efforts to cope with the impacts of changes in the atmosphere. It is therefore essential for 3 One such case is two institutional changes—privatization of state firms and decreased public expenditures—happening during the 1990s in Mexico City. They were aimed at eliminating inefficient and insolvent enterprises, thereby reducing public expenditure. Those transformations became one of the drivers of the shift in mode share from Metro and buses to minibuses and low-capacity modes, by this in increasing GHG emissions by the transportation sector (Romero Lankao et al., 2005).

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Understanding Multiple Environmental Stresses: Report of a Workshop vulnerability assessments to address multiple drivers and stresses that interact across a variety of scales. One tool is under development within the IPCC community and intends to deal with the future: the tolerable windows approach. This tool selects an exposure unit and classifies the potential outcomes either as acceptable or adverse. The next step is to try to define the dynamic combination of environmental and socioeconomic and institutional stresses that could result in negative outcomes. For this it is necessary to develop scenarios of the future that include not only environmental stresses but also socioeconomic stresses (Toth, 2001). Livelihood analysis is another multidimensional concept applied to both rural and urban studies. It pays attention to the way in which a living is obtained and gives especial consideration to agency. Livelihood analysis comprises “the capabilities, assets (stores, resources, claims, and access) and activities required for a means of living” (Ellis, 2000). The tool is useful to study how individuals, households, and communities in cities adapt to the impacts of changes in the composition of the atmosphere. It pays attention to the social, economic, institutional, and environmental dimensions of adaptation strategies by those agents; it explores how those dimensions interact at different scales. This tool can offer insights to design policies aimed at both enhancing adaptation to the impacts of atmospheric changes and reshaping the socioeconomic impacts of existing urban development pathways. I would like to close this paper with one citation and some thoughts on the role of institutions in adapting to the impacts of changes in the composition of the atmosphere. According to Steffen et al. (2003): The current states of vulnerability research and vulnerability assessment exhibit both the potential for substantial synergy in addressing global environmental risks … as well as significant weaknesses which undermine that potential. A substantial base of fundamental knowledge has been created. However it is highly fragmentary in nature, with competing paradigms, conflicting theory, empirical results often idiosyncratic and tied to particular approaches, and a lack of comparative analysis and findings. My guess is that one research path for us is to develop meta-analytic tools to tease out the paradigms behind those approaches and to see whether and, if so, at which levels it is possible to make those analyses and their findings comparable. INSTITUTIONS Last but not least, institutions play a significant role both as drivers/stressors (IDGEC, 2005; Romero Lankao et al., 2005) and as enhancers of urban systems’ ability to cope with and adapt to the negative impacts of changes in atmospheric

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Understanding Multiple Environmental Stresses: Report of a Workshop composition and land use (IDGEC, 2005). As already mentioned in this paper the first task we are confronted with is to understand within an integrated perspective the pathways through which institutions together with other socioeconomic and environmental processes influence livelihoods, economic activities, urban life, migration, and other realms where adaptive capacity takes place in cities. The second and more difficult task is to consider existing research on the science policy interface, which may help us understand why and how decision makers relate to scientific information and findings on socioeconomic and institutional impacts of changes in land use and in atmospheric composition; the resources and institutional capacity decision makers have to design and implement adaptation strategies; the role of other organizations, institutions, and stakeholders in the design and implementation of adaptation strategies. REFERENCES Barkin, D., con la colaboración de Adriana Zavala. 1978. Desarrollo regional y reorganización Campesina: La Chontalpa como reflejo del problema agropecuraio mexicano. Mexico: Editorial Nueva Imagen. Bruchner, T., G. Petschel-Held, F. L. Tóth, H.-M. Füssel, C. Helm, M. Leimbach, and H.-J. Schellnguber. 1999. Climate change decision-support and the tolerable windows approach. Environmental Modeling and Assessment 4:217-234. Ellis, F. 2000. Rural Livelihood and Diversity in Developing Countries. Oxford: Oxford University Press. Kaneko T., and Y. Matsouka. 2003. Driving forces behind the stagnancy of China’s energy related CO2 emissions from 1996-1999: The relative importance of structural change, intensity change and scale change. Draft Nakicenovic, N. 2004. Socioeconomic driving forces of emission scenarios. Pp. 225-239 in The Global Carbon Cycle: Integrating Humans, Climate and the Natural World, C. B. Field and M. R. Raupach, eds. Washington, D.C.: Island Press. Rees, W., and M. Wackernagel. 1996. Urban ecological footprints: Why cities can not be sustainable—and why they are a key to sustainability. Environmental Impact Assessment Review 16:223-248. Romero Lankao, P., H. López Villafranco, A. Rosas Huerta, G. Günther, and Z. Correa Armenta, eds. 2005. Can Cities Reduce Global Warming? Urban Development and the Carbon Cycle in Latin America. México, IAI, UAM-X, IHDP, GCP. 92 pp. Steffen, W., A. Sanderson, P. D. Tyson, J. Jäger, P. A. Matson, B. Moore III, F. Oldfield, K. Richardson, J. Schellnhuber, B. L. Turner II, and R. J. Wasson. 2004. Global Change and the Earth System: A Planet Under Pressure. Berlin, Heidelberg, New York: Springer-Verlag. Dr. Patricia Romero Lankao is a professor in the Department of Politics and Culture at the Autonomous Metropolitan University, Campus Xochimilco, in Mexico City, Mexico. Her general field of expertise and interest is in the interface of the human dimensions of global environmental change. She has published on

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Understanding Multiple Environmental Stresses: Report of a Workshop issues such as the design of Mexican environmental policy, water policy in Mexico City, environmental perceptions and attitudes toward public environmental strategies and instruments, and vulnerability to climate variability and change among farmers and water users. Dr. Romero, a sociologist by training, has two doctoral degrees, one in regional development from the Autonomous Metropolitan University and one in agricultural sciences from the University of Bonn, Germany.

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Understanding Multiple Environmental Stresses: Report of a Workshop UNDERSTANDING VULNERABILITY OF ECOSYSTEM GOODS AND SERVICES AND RESPONSE STRATEGIES Richard B. Norgaard University of California, Berkeley Questions suggested: (1) What has been the economic impact of large-scale stresses to ecosystems, and how has this impact been characterized? (2) How is vulnerability of ecosystem goods and services characterized? (3) How best can society value ecosystems and ecosystem goods and services to effectively prepare for the impact of multiple stresses? BROAD RESPONSE It is important to approach these questions from a dynamic systems perspective within which environmental and socioeconomic systems are interacting over time, each affecting the other. Economic impacts are not simply “there” to be identified by the economist but rather are a product of prior conditions. Thus the economic impact of large-scale or multiple stresses is very dependent on how well we are prepared for and how well we respond to the stresses. Hurricane Katrina laid bare the human and economic costs of being ill prepared and unresponsive. The critical point here is that a particular stress, or particular combination of stresses, does not map to a particular economic impact. Between a stress and an impact there are typically human-modified environments, technological systems, and socioeconomic institutions and capabilities whose states and hence responses to stresses depend on both preceding stresses and human decisions to recognize, develop, and protect environmental qualities, technological capacities, and institutional capabilities. Thus the economic implications of an extended drought in the Midwest that seriously jeopardized corn, soybean, and wheat production depends on the existence, or not, of the agroecological, technological, and socioeconomic conditions necessary to raise alternative grains that are quite normally grown, for example, in arid regions of India. The definition of a drought (i.e., is there enough water?) is not simply a matter of the difference between rainfall and crop needs, or between soil storage, rainfall, and evapotransporation. Need, evapotransporation, and soil storage depend on the crops grown. As we saw in the case of Katrina, the distribution of income can also critically affect the impacts observed. The human toll of an extended drought in the Midwest could be no more than the discomfort of foregoing beef and eating soy burgers. During the stress of World War II, margarine became a normal food in the American diet through programs that restricted the availability of butter for all. But if the rich continue to eat beef through a drought, the price of grains could quickly become a major hardship on the poor.

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Understanding Multiple Environmental Stresses: Report of a Workshop Similarly, there are scalar issues associated with risk that are critical. Historically, near-subsistence farmers planted a variety of crops in the expectation that some of them would fit the weather conditions of a particular year. With trade and specialization, risks and risk reduction strategies become distributed more globally. Thus, low corn, soybean, and wheat yields in the United States in any particular year or decade are dampened by global production unless, as is possible with climate change, much of the globe is affected in the same period. A rapid transition in climate conditions could also occur globally such that globalizing risk becomes a less effective strategy. We should be as concerned about combinations of social and environmental stresses as about combinations of environmental stresses. It was much more difficult to be prepared for and to respond to the combination of stresses known as the “dust bowl” during the Great Depression because the social system was already highly stressed by a dysfunctional economy. No doubt environmental stresses during World Wars I and II also resulted in greater hardship because social system resources were devoted to the wars. It is also important to keep in mind that the social conditions, specifically the movement of soldiers and material at the end of World War I, helped spread the Spanish Flu virus, which ended up killing 10 times as many Americans as the Great War. We have a tendency to think of fair to good socioeconomic times as normal and bad as the exception, but surely 20 percent of the years in the United States during the 20th century were pretty bad. And just as surely, 20 percent of the world’s population at any one time is engaged in a civil or regional war or having bad economic times. Yet most of our scenarios for “sustainable development” are built around fair to good times being an uninterrupted norm. Acknowledging the dynamic interactions between social and environmental systems has not yet led to the incorporation of appropriate models to address periodic stresses in environmental assessments, let alone combinations of stresses. Efforts to date to portray the interactions between social systems and environmental systems in assessments tend to forecast alternative smooth scenarios. For example, the assessments by the Intergovernmental Panel on Climate Change are tied to alternative scenarios that differ, for example, by overall rates of growth, types of technology, and differences between industrialized and less industrialized countries, but these scenarios play out without discontinuities. The scenarios of the Millennium Ecosystem Assessment are more heuristic and the differences between them with respect to resilience overall, patchiness globally, and protection of the poor to stresses are discussed but not actually quantified. Valuation of ecosystem services as a technique has also presumed a steady forecast of good times, both environmentally and socially (at least for the rich). Because a dollar of a poor person tends to be counted the same as the dollar of a rich person, ecotourism values, for example, can swamp subsistence ecosystem services important to the poor. Clearly it is these more basic values that are more important to be studying now that we are more concerned about multiple stresses.

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Understanding Multiple Environmental Stresses: Report of a Workshop In any case, we value what we know, and as the uncertainty of the future becomes more clear to more people, we will value ecosystem services differently. This is rather a circular problem, for we want the values to inform people of the importance of ecosystem services. But to the extent that some of the ways economists derive values flow from an informed public expressing choices, most ecosystem services, especially under conditions of stress, are highly undervalued because people are less aware of the importance of the services than they should be. Richard B. Norgaard is a professor in the Energy and Resources Program at the University of California, Berkeley. His areas of expertise include environmental epistemology; ecological, environmental, and resource economics; environment and development in less developed countries; development as social system and ecological system coevolution; tropical rain forests; pest management; petroleum development; and water development. His recent research addresses how environmental problems challenge scientific understanding and the policy process, how ecologists and economists understand systems differently, and how globalization affects environmental governance. Dr. Norgaard received his Ph.D. in economics from the University of Chicago.

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Understanding Multiple Environmental Stresses: Report of a Workshop PATTERNS, SOURCES, AND IMPACTS OF DECADAL-TO-MULTIDECADAL CLIMATE VARIABILITY IN THE WEST Julio L. Betancourt4 U.S. Geological Survey Desert Laboratory Both instrumental and tree-ring records show that the western U.S. climate exhibits low-frequency modes in the form of persistent and widespread droughts that alternate with pluvials. Some notable examples are the dry Medieval period (A.D. 900-1300) and the ensuing wetter Little Ice Age (A.D. 1400-1850); the dramatic switch from the megadrought in the late 1500s to the megapluvial in the early 1600s; and the bracketing of epic droughts in the 1930s and 1950s by two of the wettest periods (1905-1920 and 1965-1995) in the last millennium. Such decadal-to-multidecadal (D2M) hydroclimatic variability is assumed to operate through the oceans and clearly can occur independent from anthropogenic forcing. Statistical and modeling studies show teleconnections to low-frequency SST variability in the Pacific, Indian, and North Atlantic Oceans, and there is mounting interest in both mechanisms and predictability. D2M precipitation variability in the western United States tends to be spatially coherent and can synchronize physical and biological processes in ways that are complex and difficult to forecast and monitor. D2M variability can synchronize fluctuations in surface water availability across major basins and can thus overextend regional drought relief and interbasin transfer agreements. Traditionally, both water resource and floodplain management in the West have been based mostly on stationary assumptions about surface flow—that the mean and moments of the annual or peak discharge distributions do not change over time. Federal flood insurance relies on the concept of the 100-year flood, which is calculated routinely with flood frequency methods that assume stationarity. And we also assume stationarity in annual operations of critical water resources. For instance, Article III of the Compact apportions 7.5 million acre feet (MAF) per year each to the Upper and Lower Colorado River Basins, stipulates that Upper Basin states cannot deplete the flow at Lees Ferry by more than 75 MAF over a period of 10 consecutive years and mandates a moving 10-year average release of 8.23 MAF/year from Lake Powell into the Lower Basin. In the case of D2M variability, 100 years may not be long enough to evaluate stationary assumptions in water resource planning, and we are forced to rely on tree-ring reconstructions of precipitation and streamflow. These reconstructions vary in coverage and quality, but nonetheless are a good first approximation of the history and long-term probability of D2M precipitation and streamflow regimes. In particular, probability distribution functions from long reconstructions of hydroclimate (precipitation or 4 Dr. Betancourt was unable to attend the workshop; his slides and perspectives were integrated into Jonathan Overpeck’s presentation.

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Understanding Multiple Environmental Stresses: Report of a Workshop streamflow) or climatic index series (AMO, PDO, etc.) can be used to calculate the occurrence and return probabilities of climatic episodes. This information can then be mapped to decisions about annual water resource operations or facilities planning. By synchronizing ecological disturbances and recruitment pulses, D2M variability also plays a key role in structuring woodland and forest communities in western watersheds. In the event of longer, hotter growing seasons, D2M variability will still determine the timing and pace of ecosystem changes. Oscillations between warm-dry and warm-wet regimes will continue to produce uncommonly large disturbances followed by accelerated regeneration and succession. Such large-scale vegetation changes will have complex hydrological effects and will add further uncertainty to water resource availability. A principal challenge for land managers in the 21st century will be to manage for disturbance and succession in purposeful and systematic ways that promote asynchrony and patchiness at local to regional scales while still preserving goods and services that ecosystems provide. Julio L. Betancourt is project chief, National Research Program, Water Resources Division, U.S. Geological Survey and adjunct professor in the Departments of Geoscience and Geography at the University of Arizona. The focus of his research is ecosystem and watershed responses to climate variability on different temporal and spatial scales. Dr. Betancourt received his Ph.D. in geosciences from the University of Arizona, Tucson.