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Initial Research Priorities for U.S. Participation in the IGBP In this chapter, the committee identifies a number of the most critical gaps in our understancling of global change that most ur- gently need to be addressed in the initial U.S. contributions to the IGBP. The several research initiatives that are recommended in this chapter provide a framework for U.S. contributions to the IGBP in the current planning stage of the program's development. These rec- ommendations are not intended to include all future research needs for the program, but are intended to emphasize those issues not being addressed by ongoing programs. The committee adopter! the following criteria for selecting these initial research initiatives: ~ The issue must be global in nature, and research conducted on the topic must be expected to lead rapidly to a greater understanding of global environmental change. ~ The magnitude and breadth of the issue must transcend the boundaries of existing research programs and discipline-oriented en- deavors, making it unlikely that it-can be addressed within traditional disciplinary studies. ~ The issue must be amenable to research, with significant progress expected in a period of a few to 10 years or with immediate initiation required in order to build the Tong-term monitoring and 13

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14 research base needed for sustained progress in understanding global change. The research initiatives are recommender! on the basis of the committee's systematic review of the current state of knowledge from five perspectives on the earth system: climatic and hydrologic systems, ecological systems and dynamics, biogeochemical dynamics, the human dimension of global change, and earth system history (see the background papers in Part II for detailed discussions). From these analyses particularly from analysis of the interactions among these five components of the earth system and from a review of related ongoing programs, the committee identified a number of questions about key relationships that are currently insufficiently understood but essential to improving scientific abilities to predict global change, for example: ~ How is the climate system coupled to the dynamics of terres- trial ecosystems, and, specifically, what are the feedbacks between ecosystem dynamics and the hydrologic component of the climate system? What factors control fluxes of radiatively active gases be- tween the land and atmosphere and fluxes of biologically important elements from land to aquatic systems? What are the feedbacks between climate change and fluxes of these materials? What are the fluxes of biogenic substances from the upper ocean to both the atmosphere and the deep ocean? How do these fluxes affect climate, and how does climate change affect these flux rates? How is the coupling of human and enviornmental systems altered by long-term global trends in social, economic, and techno- logical development? How is the coupling altered by environmental change itself. RESEARCH INITIATIVES FOR EARLY IMPLEMENTATION . Answering these key questions about the earth system demands improved understanding of the influences of terrestrial and oceanic biota on the climate system, and the interactions with the hydrologic cycle, nutrient supply and transport, and surface climate conditions. Answers also depend on an understanding of how anthropogenic activities generate trace gases through changing land use, energy production, and industrial processes.

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15 The committee recommends that these gaps be addressed through major research initiatives on each of the following topics: Water-energy-vegetation interactions the coupling between the climate system, especially its hydrological processes, and the dynamics of terrestrial vegetation. ~ Fluxes of radiatively active trace gases and nutrients to and from the terrestrial biosphere. Biogeochemical dynamics in the ocean that regulate formation and influence the ocean's capacity to sequester or release radiatively active gases, such as carbon dioxide and organic sulfur species, and their interactions with climate. Earth system history and modeling to reconstruct the record of the past preserved in ice cores, sediment deposits, and other proxy indicators of change. Human interactions with the gloom environment to document and analyze land use changes and changes in industrial production and consumption over the past several hundred years, and to create useful scenarios of future changes in the processes that drive global change. Issues that need to be addressed in each of these initiatives are discussed below. These discussions, however, only outline the broad initiatives that should be pursued and illustrate the types of experiments, modeling efforts, and observations that wiB be required. Detailed research plans and schedules must be formulated by groups of experts engaged in the relevant research disciplines. Water- Energy-Vegetation Interactions The committee recommends an observational and research project a water-energy-vegetation experiment to study the cou- pling between the climate system, especially its hydrological pro- cesses, and the dynamics of terrestrial vegetation. The initiative has two objectives: (1) to develop validated global models of the response of terrestrial ecosystems to climate, water and land use change, atmospheric chemistry, and other global- or regional-scale stress factors such as changing atmospheric composition, fires, her- bivory, and disease; and (2) to determine how ecosystem structure and function affect evapotranspiration, soil moisture, and surface runoff on regional and global scales. The project would in essence be the biological complement to the Global Energy and Water Cycle

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16 Experiment (GEWEX), whose planning is just now beginning under the WCRP. This research initiative will require field and laboratory experi- ments, modeling efforts, and observations to address the response of ecosystems to climate changes, as well as the response of climate to ecosystem change. Included would be the following: Experiments on whole ecosystems in order to quantify effects of climate change and other stress factors. ~ Studies to scale up information on nutrient cycling and plant physiological processes to the level of the whole ecosystem, taking into account the dynamics of key species. ~ Recovery of records of past vegetation cover and other intli- cators suitable for validating the long-term hydrological response of climate models to global change. ~ Development of models of global and regional climate that emphasize hydrological and land surface processes (using parame- terizations derived and validated by field data and process studies) and that can be used to study the sensitivity of climate processes to vegetation changes. Analysis of the human causes and effects of changes in the hydrologic cycle, including documenting past and projecting future human activities important for the hydrologic cycle; defining those aspects of hydrologic change most important for human activities; and (leveloping frameworks for application of hy(lrologic projections to environmental assessment and management. ~ Observations at a global scale of seasonal and interannu~ variations in vegetation cover and evapotranspiration. A regional focus to study the coupling between vegetation and the hydrologic cycle in particularly important or sensitive geographic regions such as the Amazon Basin, the taiga-tundra transition zone, and the western United States is an important component of this initiative. Such a focus includes projections of the impacts of changes in terrestrial hyclrologic processes on ecosystem composition and ~ , - ~ unctlomng in speclnc regions. The initiative also requires strong input from other international research programs, such as GEWEX and the International Satellite Land-Surface Climatology Project (ISI:SCP), to address the ques- tions of global distributions of rainfall over land and atmospheric properties important for surface evapotranspiration.

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17 Fluxes of Radiatively Active Trace Gases and Nutrients to and Mom the Terrestrial Biosphere The committee proposes a research initiative focused on the fluxes of materials such as (1) radiatively active trace gases to and from the terrestrial biosphere, and (2) nutrients from land to aquatic and marine ecosystems. The objective of a research focus on radiatively active trace gas exchange between the terrestrial biosphere and the atmosphere is to improve understanding of those basic ecosystem processes that determine gas fluxes. This understanding is needed to construct functional models that can be used to predict how climate and land use change wiD alter emissions and absorption of radiatively active trace gases from the biosphere and, in turn, feed back to further changes in climate. The research should emphasize methane, carbon dioxide, and nitrous oxide, but other significant constituents, e.g., ammonia and organic compounds, are also of concern. The initiative will require the following: Experiments involving plants, soils, and peats to improve un- derstanding of processes affecting gas exchange between them and the atmosphere, such as changes in carbon storage; the influence of nutrient availability; the influence of population dynamics through nitrogen fixation, and microbial processes; hydrological influences on partitioning between production of carbon dioxide and methane and between nitrogen and nitrous oxide; and the influence of the chemistry of precipitation on such processes. Experiments on in- tact ecosystems that include the biota and soils will also be needed to measure the effect of environmental changes on the complex, in- teracting processes of vegetation change, nutrient cycling, and gas fluxes. Larger scale ecosystem experiments can involve, for example, manipulations of entire watersheds or can use natural or inadvertent anthropogenically induced perturbations for experiments. Investigations at local or regional scales, particularly in ecosys- tems such as the Arctic and the tropics that play significant roles in global change. A local and regional focus, including compara- tive studies along environmental gradients, is needed in order to extrapolate predictions of gas emissions to the global scale after a mechanistic understanding of gas emissions is achieved. Models that combine descriptions of the functioning of whole ecosystems (process-functional approach) with descriptions of changes in populations and communities within ecosystems (popula-

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18 tion-community approach), in order to predict the changing patterns of fluxes from ecosystems subjected to rapid change. Because this new generation of models wiB be mechanistic, they could be used to extrapolate beyond existing or past conditions, and to predict gas emissions from new combinations of vegetation, soils, climate, land use, and atmospheric processes. Increased attention to documentation of past ecosystems from the record of the past, in order to understand better the range of ecosystem form and function that could develop in the future in response to global change. Documentation on a global scale of the history of land uses believed to be sources of methane and other trace gases, and as- sessments of future changes in human activities that can result in changes in emissions. Similarly, prehistoric and historic activities that have affected carbon storage in vegetation and soils should be documented on a global scale. The component of this research initiative focused on fluxes of nu- trients from terrestrial to aquatic systems will, in addition to study- ing nutrient transfers in natural ecosystems, emphasize the effects of land use change on the amount and pathways of nutrient losses from terrestrial ecosystems. The objective is to broaden the initiative on trace gas emissions to include analysis of how global changes now under way will affect the transfer of nutrients to riverine, estuarine, and ultimately, ocean systems. As discussed in the following section, changes in ocean productivity have important long-term implications for climate. Thus nutrient transfers from the terrestrial to marine systems could have important feedback effects. Transfers of materials across ecosystem boundaries will be strongly affected by various aspects of global change. I,arge-scale experiments, involving manipulations of entire watersheds or intact ecosystems, are needed to assess the effects on nutrient Tosses of floods, increased fire frequency, loss of species, and other events related to global change. Rising sea level will also affect nutrient cycling and transfer to the ocean. Superimposed on these effects, and in some systems overwhelming them, are massive changes in land use, especially in the tropics, where the human population and activity are growing rapidly. Deforestation and increased intensity of agriculture in dry and humid tropical regions are affecting nutrient availability in soils and transfers to other systems via dust and runoff. Understanding the processes underlying nutrient Tosses from ter- restrial systems will require monitored watersheds. Once baseline

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19 data are established, experiments with different kinds of land use can be carried out, with paired watersheds left unchanged as con- trols. These experiments will separate human effects from other aspects of global change. Long-term observations are necessary, as some effects are cumulative and others have long response times. Long-term studies will also increase the opportunity to observe and hence understand unusual climatic events that stress the system. The important requirements are thus as follows: ~ Experimental manipulations of drainage basins to increase understanding of the mechanisms controlling nutrient transfer via water or air from the land to streams, lakes, rivers, and eventually, the ocean. ~ Examinations of systems along a gradient, e.g., from savanna to dry forest to rain forest, in order to quantify fluxes as a function of ecosystem type. Research to follow the fate of nutrients after they are lost from terrestrial ecosystems into rivers, lakes, groundwater, the ocean, and the atmosphere. Studies of estuarine processing of nutrients loaded into rivers should be emphasized. Analysis of the patterns and causes of anthropogenic land use change, including documenting past and projecting future human activities important for terrestrial nutrient fluxes, and defining those aspects of nutrient flux most important for human activities. ~ _ _1~ 1 _ _ 1 1 1 ~ , ~ ~ . rartlcular emphasis on phosphorus In nutrient balance stud- ies. While phosphorus is less mobile and dynamic than carbon, nitrogen, and sulfur, it exerts a strong control on productivity both on land and in aquatic systems. Some approaches appear promising in the context of this research focus. For example, stable isotope signatures of carbon, nitrogen, and sulfur as tracers of element movement and as integrated reflections of the processes controlling element transformation and loss will provide important information. While this approach is relatively well worked out for carbon, considerable development of research techniques is necessary before it can be applied to nitrogen and sulfur. Better measurements of both historic and current rates and types of land conversion also need to be developed and applied. Collaboration with the research component on fluxes of radia- tively active gas, discussed above, is needed to understand, model, and predict biosphere-atmosphere interaction following land clearing.

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20 Additionally, interaction with ongoing programs such as the Inter- national Union of Biological Science's Tropical Biology and Fertility Program and the International Atomic Energy Association-Centro Energia Nuclear na Agricultura (TAEA-CENA) Amazonia ~ Project will be needed for the research focus discussed here. The overall initiative should be linked with activities of experts concerned with land use change as a primary driving force in species extinctions worldwide (see "Human Interactions" initiative below). Both the information on rates of land use change and the measure- ments of the fate of nutrients once they are lost from cleared land are fundamental to these efforts, and knowledge of the functional significance of particular species in local areas is fundamental to this initiative. Biogeochemical Dynamics in the Ocean The committee recommends a research initiative to understand and predict the effects of climate change on ocean biogeochemical cycles and their corresponding feedback to climate. 'the objective of this effort is to develop the capability to predict the effect of projected global climate change on the ocean's physical/chemical and biogeochemical processes, especially as they feed back to climate via the release or absorption of radiatively important gases such as carbon dioxide and organic sulfur species. Changes in climate over the ocean will alter the physical condi- tions of the upper ocean. Incident irradiation, evaporation/precipita- tion, and wind shears on the ocean surface help to define the mixing state, and hence the nutrient supply and residence time for plankton. Nutrient supply and re-suspension properties are important factors in determining the nature of the planktonic food web. Greater rates of nutrient supply, and higher mixing rates, for example, promote the growth of large diatoms. These two different types of plankton sustain markedly different food webs and have significantly differ- ent consequences for the residence time of photosynthetically fixed carbon in the ocean. In addition, different plankton groups have different physiologies related to sulfur metabolism and play consid- erably different roles in the evolution of organic sulfur species, which have climatic implications when liberated to the atmosphere. This effort will require a gIobaI-scaTe assessment of the processes governing the rates of primary production and determining the fate of biogenic materials in the sea. A major international program, the

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21 Joint Global Ocean Flux Study (JGOFS) is now being defined in this area. It will consist of global observations, regional process studies, coastal ocean studies, and modeling. Some of the recommendations below will probably be included in JGOFS, some should be initiated as soon as possible, while other activities, especially those related to the biogeochemical implications of the anticipated climate change, may require results of JGOFS and other ocean programs such as the World Ocean Circulation Experiment before they can be initiated. A U.S. contribution in this area should include the following: Helping to establish the global remote sensing capability and appropriate sea surface verification necessary to assess temporal and spatial patterns in plankton distribution. ~ Studying the processes responsible for the initiation of plank- ton blooms (including dependence on temperature, mixing state, and nutrient supply) and their roles in (1) the flux of organic material and calcium carbonate to the deep sea and (2) the production of organic sulfur compounds, which, when liberated to the atmosphere, have implications for climate. ~ Developing modeling and scaling techniques to generalize the results of intensive local studies of plankton blooms to characteristic regional and basin scales. ~ Placing emphasis on those high-latitude ocean regions where vertical fluxes of carbon to the deep sea and vertical fluxes of nutri- ents to the surface waters give these regions disproportionately large global significance. Investigating the biogeochemical processes responsible for forming, transporting, and preserving in ocean sediments the hard parts of plankton used in studies of past climates. ~ Initiating large-scale models of upper ocean physical and bio- geochemical processes that can be used to assess the effects of climate change on biogeochemical processes that have potential to feed back to climate via the regulation of radiatively active trace gas release from the ocean. Human Interactions with Global Change This research initiative would focus on the relatively short-term record of the period of intensive human activities that have affected the global environment. Anthropogenic changes in the earth system need to be systematically documented over the past several hundred years and analyzed as a basis for developing useful reference scenarios

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22 of future change. In particular, two aspects of human activity are es- peciaDy relevant to global change: land use changes, which influence both physical (e.g., albedo, evapotranspiration, and trace gas flux) and biological (e.g., vegetative cover and biodiversity) variables; and the industrial metabolism that transforms resources into emissions that must be absorbed and processed by the environment. Investigation of global land use patterns would involve the fol- lowing: ~ Construction of a core conceptual mode] or theory of the causal relations underlying: changes in culture be.. Copulation. de- _ _ ~ ~ ~ ~ ~ velopment values) on one hand and changes in environment on the other hand, to human choices that affect long-term, large-scale pat- terns in the use of land. Documentation of how key variables of land use, population, agricultural prices, and so on, identified in the conceptual mode! have changed throughout the world over the last several hundred years. In-depth regional case studies of the general relationships suggested in the conceptual and historical work. Construction of future scenarios of global land use change, and exploration of how alternative human choices regarding global change could alter those scenarios. Parallel to the study of global land use change, a similar approach to the study of industrial metabolism would involve the following: Construction of a conceptual model linking demographic, eco- nomic, and institutional factors with the evolution of material and energy uses, and human consumption processes relevant to global change. Documentation of how particular material and energy re- sources have been metabolized through human production and con- gumption processes over periods of decades to centuries. In-depth regional case studies of the general relationships developed in the conceptual and historical work. Construction of future scenarios of industrial metabolism and associated materials and energy exchanges with the environment. Earth System History and Modeling The initiative on earth system history and modeling is con- cerned with documenting and understanding overall patterns of global change. The initiative would focus on reconstructing the past ... .. .. . . .

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23 over tens of thousands of years to provide a data base for validating global change models. The history of atmospheric composition arid climate, and of the spatial distribution of climate, vegetation, and ocean circulation would be developed. Special attention is needed on periods of rapid change to provide insight into poorly understood system processes. A research focus on the long-term record requires the following: . Data from polar and temperate latitude ice cores, ocean sed- iments and corals with 10- to 100-year temporal resolution, and various kinds of physical and biological terrestrial records. Theoretical studies and modeling to establish quantitative relationships between measured parameters and physical processes, in order to better interpret the record of the past. Sensitivity studies with global models to define the spatial and temporal resolution needed in the study of the record of the past and to suggest which types of data should be collected. ~ Development and improvement of global change models based on observations from the record of the past. Models can use infor- mation from the past record such as climate and vegetation and indirect measures of the carbon cycle. Past abundance of carbon dioxide, methane, carbon-13 and other stable isotopes, and other chemical species accessible from the record can be used for model validation. Data on the history of human interactions with the earth system, as developed in the previous initiative, will also be useful. Close collaboration between observational and modeling activities is essential. DEVELOPMENT OF RESEARCH INITIATIVES Two streams of activity are required to develop the research initiatives for the U.S. contribution to the IGBP into detailed plans for research programs: (1) involvement of scientists with particular expertise to develop the research plans, and (2) support of those related activities essential to the success of the IGBP. Steering groups should be established on each of the five research initiatives proposed above as research foci for the initial contribution to the IGBP. These groups should be closely coordinated with other relevant activities in the National Research Council. These steer- ing groups, operating under the Committee on Global Change over approximately the next two years, would engage scientists with the relevant expertise to further define programs of coordinated research

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24 in the respective area. The Committee on Global Change would en- sure that the research plans developed by each group are coordinated into an overall plan for the U.S. contribution to the IGBP. Support for existing programs related to the goals for the IGBP is also an integral part of the U.S. effort. Three categories of support can be identified: 1. As noted above, U.S. contributions to the IGBP are drawn from the broad suite of U.S. observational and research programs that have been described as the U.S. effort on global change. The U.S. program is based on the concept developed in the report of the NASA-sponsored Earth System Sciences Committee that study of the earth as an integrated system is an important and timely paradigm for the earth sciences. Strong support for such a broad national effort in the study of the earth is an essential foundation for the focused programs addressed in this report. 2. A number of existing, ongoing programs have objectives and weD-developed plans that clearly fall entirely or partly within the scope of the IGBP or the broader U.S. global change efforts. Among these are UNESCO's Man and the Biosphere Program, the several projects of the Scientific Committee on Problems of the Environment related to global change, and the United Nations Environment Pro- gram's Global Environmental Monitoring System (GEMS). Particu- larly relevant and essential are the components of the World Climate Program. One of these, the World Climate Research Program, or- ganized under the World Meteorological Organization (WMO) and ICSU, focuses on dynamic and hydrological processes in the climate system and has in planning or in progress a number of well-conceived projects (e.g., Global Energy and Water Cycle Experiment, World Ocean Circulation Experiment, Tropical Ocean/GIobal Atmosphere Program, International Satellite Cloud Climatology Project, and In- ternational Satellite Land-Surface Climatology Project) that promise to contribute greatly to the goals of the IGBP. The contributions of the Data, Applications, and Impacts components of the World CTi- mate Program should also be emphasized. The IGBP and these existing activities are highly complementary en cl mutually support- ~ve. The challenge is to harmonize and coordinate the practical work of the various planning bodies so that each activity can be effec- tively focused on appropriate objectives. Such an approach was successfully employed in the Global Atmospheric Research Program (GARP), where the WMO/ICSU Joint Organizing Committee, the

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25 ICSU Committee on Space Research, the International Association of Meteorology and Atmospheric Physics' (lAMAP) Radiation Com- mission, and other bodies pursued closely coordinated programs. Interaction within this family of closely related activities in the earth sciences should be strengthened, coordinated, and enhanced. 3. Support for discipline-oriented research related to the goals of the IGBP is needed to bolster the scientific foundations of the program. For research centered on the atmospheric and oceanic components, a long and mature history of previous studies and an array of coordinated research programs provide good foundations for contributions to the understanding of global change. In other areas, such as the biological and human components of global change, the existing research program is less wed developed. The relevant research communities should be encouraged to develop their own internally justified research priorities relevant to global change. An aggressive program to support research in these as well as other related disciplines is needed. For instance, a number of areas of needed research are highlighted in the background paper on ecological systems and dynamics (see especially the section on principal issues and research challenges). These include (1) research on physiological responses of plants and animals to the environment, especially to multiple stresses; patterns of genetic variability, including the development of theory regarding evolutionary responses to rapid environmental change; the direct ef- fects of elevated carbon dioxide concentrations on intact ecosystems; and characteristics that allow some species to adjust geographical ranges rapidly in the face of change while others become extinct; (2) monitoring of ongoing changes in distributions that may record the incipient effects of global change and of ongoing changes in Tend use; and (3) development of more complete paleorecords, particularly from littIe-explored parts of the earth. The existing research program on the human components of global change is also inadequately developed, as discussed in the background paper on the human dimension. Efforts to bring to- gether natural, social, behavioral, and engineering scientists to ex- amine in-depth the research required on the human dimension of global change should be supported. Several research areas identified in the background paper integrated methods to assess the risk and implications of Tong-term environmental change for resource avail- ability at the regional scale; ways that knowledge, perceptions, and values related to global change can be more effectively brought to

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26 bear on human choices that affect global change; and evaluation and design of institutional mechanisms for better management of global change require further development in close collaboration with those relevant scientific communities in the social, behavioral, and engineering sciences that were not adequately represented in current planning activities.