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Landscapes on the Edge: New Horizons for Research on Earth’s Surface Summary S.1 INVESTIGATIONS OF EARTH’S SURFACE Earth’s surface is a dynamic interface across which the atmosphere, water, biota, and tectonics interact to transform rock into landscapes with distinctive features crucial to the function and existence of water resources, natural hazards, climate, biogeochemical cycles, and life. Interacting physical, chemical, biotic, and human processes—“Earth surface processes”—alter and reshape Earth’s surface on spatial scales that range from those of atomic particles to continents and over time scales that operate from nanoseconds to millions of years. The study of Earth surface processes and the landscapes they create is rich with open questions and opportunities to make fundamental scientific advances and to understand and predict the interactions, causes, and effects of these processes. Scientists who study Earth’s “surface processes” have a distinctive and novel ability to contribute to understanding how Earth’s surface changes with time and resolving important environmental challenges that may arise from these changes. Research in Earth surface processes has grown significantly in the last two decades, in response largely to two factors. First, scientists, policy makers, and the public have become increasingly aware of the impact of human activity and climate change on Earth’s surface. The changes to Earth’s surface affected by natural events and by humans, notably through land use, have altered the physical, chemical, and biological integrity of soils, mountains, prairies, rivers, coasts, and watersheds. Thus, society has heightened its demand for scientific guidance in making decisions concerning the future of Earth’s surface. Second, development of new analytical and computing tools has markedly increased our ability to examine Earth’s surface at high spatial and temporal resolution and to develop models that can help to understand the speed and magnitude over which surface processes interact and affect changes. Recognizing the growing importance of understanding Earth’s surface and the processes that shape it, the National Science Foundation (NSF) requested the National Research
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface BOX S.1 Statement of Task Earth’s surface is a dynamic interface where physical, chemical, biological, and human processes cause and are affected by forcings in the Earth system. This impact-feedback loop occurs over a wide range of temporal and spatial scales. It binds the Earth’s surface to a host of scientific and societal issues, and within this context the committee will: Assess the state of the art of the disciplinary field of Earth surface processes and the fundamental research questions in the field; Identify rate-limiting challenges or opportunities for making significant advances in the field; and Identify the necessary intellectual collaborations and high-priority needs to meet these challenges. Council (NRC) to establish a committee to address challenges and opportunities in Earth surface processes (Box S.1). In response to its charge, the committee has identified nine overarching scientific challenges for increasing our understanding of Earth’s surface processes and has established four high-priority research initiatives drawn from these challenges. The four research initiatives emphasize the dynamic interactions among the various processes operating on Earth’s surface and require fundamentally new interdisciplinary research approaches to develop and support them. Designed to transform and strengthen the field of Earth surface processes, the initiatives represent promising pathways to meet urgent demands for scientific guidance on issues related to planning, mitigation, and response to changes in Earth’s surface now and in the future. Some of the key intellectual and technical barriers to advance these research initiatives also are identified, as are strategies to overcome these barriers. Because the committee comprised primarily Earth scientists, the focus of the report is on the terrestrial Earth surface. S.2 GRAND CHALLENGES IN EARTH SURFACE PROCESSES Each of the nine grand research challenges identified by the committee is presented in the form of a primary research question with associated opportunities for further investigation. The grand challenges are representative of exemplary, interdisciplinary research areas in Earth surface processes deemed by the committee as poised for significant advances. The list is not intended to be a comprehensive list of all important research activities in Earth surface science:
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface What Does Our Planet’s Past Tell Us About Its Future? This challenge highlights the extent to which Earth’s surface system records its own evolution, how that record can be tapped to understand changes in the surface environment through time, and thus how Earth’s surface may change in the future. Some of the key opportunities within this challenge include (1) accelerating the ability to reconstruct past Earth surface history quantitatively through the examination, for example, of detailed sediment or ice core records and (2) measuring the rate of surface change through application of surface-dating methods. How Do Geopatterns on Earth’s Surface Arise and What Do They Tell Us About Processes? Earth surface processes create myriad spatial patterns at all scales—from microscopic fabrics observed in soils, to the repeated patterns of sand dunes and barrier islands. An unmistakable human footprint also is evident on many landscapes. These geopatterns often are self-organized—emerging spontaneously from local interactions rather than being imposed by some outside influence—and dynamic, in that they develop and evolve over time. They also are resilient; unstable patterns do not persist. Landscape geopatterns provide a template for understanding a broad spectrum of processes on the land surface. This understanding can be used to improve predictions of the response of the Earth’s surface to natural and human-induced changes. How Do Landscapes Influence and Record Climate and Tectonics? One of the major advances in the Earth sciences of the last two decades is recognition of both broad and more subtle connections between climate and tectonic systems. Some of the most intriguing research questions in the interaction of landscapes, climate, and tectonics center on the relative sensitivity and rates of the numerous feedback mechanisms among climate, topography, ecosystems, physical and chemical denudation, sedimentary deposition, and the deformation of rocks in active mountain belts. Four research opportunities emerge as particularly promising to advance understanding of these linkages: (1) quantification of the role of climate in surface processes; (2) influence of mountain building and surface processes on climate; (3) sedimentation and mountain building; and (4) interactions of surface processes, climate, tectonics, and mantle dynamics. How Does the Biogeochemical Reactor of the Earth’s Surface Respond to and Shape Landscapes from Local to Global Scales? Chemical erosion and weathering of bedrock and soil are major factors in Earth surface processes because of their potential effects on climate, the chemistry of groundwater and rivers, the strength of rocks, the erodibility of landscapes, the availability of nutrients in soils, the fate of anthropogenic contaminants, and the properties of ecosystems. Nonetheless, the breakdown of bedrock and soil is among the least understood of the important geological processes, perhaps most significantly with respect to the manner in which biogeochemical reactions affect carbon cycling. Understanding the biogeochemical
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface cycling of elements needed by biota and essential to Earth’s climate in the present and the past will allow better understanding, for example, of the magnitude of the effects of human-induced land-cover change on the balance of biogeochemical cycles. Advances in technologies to monitor and analyze biogeochemical changes in shallow subsurface geophysics, in geobiology, in nanogeoscience, and in rock mechanics will help to move research in this area from correlation to explanation and from observation to prediction. What Are the Transport Laws That Govern the Evolution of the Earth’s Surface? A mechanistic (quantitative and process-based) understanding of links among climate, hydrology, geology, biota, land use, topography, and rates of erosion and deposition is a fundamental goal of Earth surface process research. To tackle this challenge we need to discover, quantify, test, and apply mathematical laws that define the rates of processes shaping Earth’s surface. Significant progress has been made recently in developing and applying laws for the mass transport of soil on hillslopes and river incision into bedrock. However, we still lack transport laws for such fundamental processes as landsliding, overland flow erosion, glacial erosion, chemical erosion, and transport and deposition of mud. The breakdown of bedrock into erodible debris, the first step in hillslope erosion, also is poorly understood. The study of landscape history is essential for testing landscape evolution theories. How Do Ecosystems and Landscapes Coevolve? Life—through digesting, dilating, exhaling, decaying, pushing, and weaving—strongly influences the form and pace of surface erosion and modulates biogeochemical cycling, with simultaneous effects on climate, hydrology, erosion, and topography. Recent developments indicate that we are in a position to make significant advances in understanding the coevolution of landscapes, life, and ecosystems. New opportunities to investigate these interactions are found in the emerging fields of geobiology, ecohydrology, and ecogeomorphology. Coordinated efforts that explicitly address linkages among biota, Earth surface processes, and landforms are under way at field observatories. However, a need exists for greater mechanistic understanding of life-landscape interactions in order to make modeling predictions and perform experiments to explore and discover the causes, effects, rates, and magnitudes of these interactions. What Controls Landscape Resilience to Change? The shapes of landforms and their rates of evolution fluctuate within ranges, reflecting the stochastic nature of the processes that drive their operation. However, when conditions change with sufficient magnitude and duration, landscapes may become altered beyond the range within which they can recover. The driving agents have then exceeded the resilience of the landscape. Some areas of the Earth’s surface are more vulnerable than others to changes in state. Polar, glacial, and periglacial regions, for example, currently are nearing, or are in, a change of state predicted to continue with global warming. This
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface research challenge highlights the state of scientific knowledge related to rapid and abrupt change on Earth’s surface and to the factors and processes that control the resilience of landscapes to change. The science goals include identifying thresholds of change, understanding the environmental processes most vulnerable to change, understanding the mechanisms that make some landscapes resilient to change, and investigating options for mitigating or even reversing the effects of change. Studying the impact of abrupt changes on Earth’s surface requires examining both geologic and recent records of their occurrence. How Will Earth’s Surface Evolve in the “Anthropocene”? The environmental impacts of human activities are pervasive. The term “Anthropocene” has emerged in the scientific literature to suggest the onset of a new geologic era in which humans have become dominant. This overprint of human actions on Earth’s surface has made even the identification of “natural” landscapes difficult. Understanding, predicting, and adjusting to changing landscapes increasingly altered by humans constitute pressing challenges that fall squarely within the purview of Earth surface science. Mechanistic models that account explicitly for human-landscape interactions are needed, especially for adaptive management and for assisting decision making in the face of change. Science is far from developing a general theory of coupled human-natural systems, even though such a theory may offer the potential to slow or reverse environmental degradation. Because such a theory would include knowledge of societal perceptions of environmental impacts and the ability and willingness of societies to react to these changes, much focused inductive and empirical work is still required to investigate these interacting processes in a range of Earth surface environments and human societies. How Can Earth Surface Science Contribute Toward a Sustainable Earth Surface? With increasing scientific understanding of the causes and cumulative, long-term effects of human-induced changes to Earth’s surface, a consensus has emerged that at least some of these disrupted or degraded landscapes can and should be “restored” or “redesigned”. Specific research challenges arise about the size and geometry of redesigned rivers, tidal creeks and inlets, deltas, and beaches and how they are controlled by the expenditure of flow energy and by sediment supplies. Landscape restoration is a complex, high-priority goal for many researchers, practitioners, policy makers, and the public. These different communities have only recently begun to examine together the successes and limitations of past restoration efforts using new data from specific regions of Earth’s surface. Earth-surface scientists can contribute to these efforts as restoration activities move toward quantitative models and predictions. This research will provide guidance for future decisions regarding both natural and managed landscapes and will be critical for enhancing the goods and services that Earth’s surface provides for society.
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface S.3 FOUR HIGH-PRIORITY RESEARCH INITIATIVES Overarching elements of the nine grand challenges in Earth surface processes research are synthesized into four major research initiatives. Timely and rich in scientific merit, these high-priority research areas are expected to transform the field of Earth surface processes. Because the initiatives emphasize the interacting physical, chemical, biological, and human processes on Earth’s surface, they will require coordinated, sustained, interdisciplinary approaches to develop new intellectual collaborations among scientists, and to generate new scientific approaches, tools, and models. The emerging science of Earth surface processes remains challenged by intellectual and disciplinary barriers that have fragmented research in this area in the past and by the fact that the science often has relied on fairly simple, descriptive approaches. A variety of mechanisms existing within NSF could provide the research support necessary to help develop the initiatives. The scientific objectives of each initiative are described below, together with specific examples of implementation mechanisms to establish and support these initiatives. Interacting Landscapes and Climate A major research initiative in the area of climate-landscape interactions (Box S.2) would develop a quantitative understanding of climatic controls on Earth surface processes and the influence of landscape on climate over time scales that range from individual storm events to the evolution of landscapes. This initiative has the potential to transform our understanding both of the role of climate in changing the Earth’s surface and of the feedbacks between surface change and climate. The primary science objectives for this initiative include the following: Development of theory for the interactions among topography, land cover, and global, regional, and local climate that determine the biogeochemically and geomorphically significant attributes of climate Development of geomorphic transport laws that explicitly account for climate and incorporate interactions with biota, including theories for river and glacier incision; production, transport, and deposition of sediment; and geochemical processes Monitoring, experimentation, and modeling of climatic controls on the weathering of rock and soil and their influence on physical erosion rates and vice versa Study of the feedbacks between global and regional climate and (1) the operation of terrestrial carbon reservoirs and (2) the controls on atmospheric dust concentration Modeling and monitoring of landscape evolution under diverse and varying climatic conditions; identification of climatic signatures in landscapes; and evaluation of thresholds of landscape response and the limits of resilience
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface BOX S.2 Potential Implementation Mechanisms: Interacting Landscapes and Climate Collaboration between Earth surface scientists and atmospheric scientists is the primary need for developing and advancing this initiative. Improved communication between these communities is essential and could be developed, for example, through the following: Workshops, joint field campaigns and summer schools involving climate scientists and Earth surface scientists that address fundamental problems of the interaction of climate and Earth surface processes Collaborative model-building efforts between climate scientists and Earth-surface scientists that may include effects of land cover for regional and microclimate modeling, wind and wave energy, and glacier dynamics Instrumentation advances that join engineers and Earth surface scientists in the development of satellite- and land-based sensors to monitor factors relating to climatic control of Earth surface processes (for example, rainfall, soil temperature, and glacier sliding velocities) Development of theories for subglacial hydrology, basal sliding of glaciers, subglacial sediment deformation, and ocean-ice interactions at ice-sheet margins Improvement of the coupling between surface processes and existing climate models, explicitly incorporating the effects, feedbacks, and conditions outlined above Quantitative Reconstruction of Landscape Dynamics Across Time Scales This major research initiative (Box S.3) is focused on developing quantitative, detailed reconstructions of Earth surface evolution from instants to eons based on information recorded in landscapes and the sedimentary record. A confluence of interest exists between developing an understanding of surface evolution over various time scales and mining the long-term, sedimentary archive for information on the variability of surface dynamics. This archive applies, in particular, to the frequency of rare but potentially catastrophic events. Reconstructed evolution of the Earth’s surface will be used (1) to test and develop models that couple tectonics, climate, biota, lithology, and landscape evolution; (2) to constrain the frequencies and causes of rare but important surface events; and (3) to provide baseline information on pre-human landscapes and their response to change as a guide for restoration and management.
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface BOX S.3 Potential Implementation Mechanisms: Quantitative Reconstruction of Landscape Dynamics Across Time Scales The necessary intellectual collaborations for this initiative to succeed are primarily those between researchers studying deep- and surface-Earth processes, from both academic and industry backgrounds. Addressing the objectives in this initiative requires (1) application and development of specific analytical techniques and tools and (2) incorporation of data acquired with these tools in coupled models. Specific mechanisms to foster these collaborations include the following: Development of natural deep-time laboratories to focus on reconstruction of Earth surface evolution from short-term to geologic time scales Targeted projects with joint industry and academic participation, organization, and products to apply noncommercially sensitive portions of three-dimensional seismic surveys to key initiative objectives Continued development of cosmogenic, optically stimulated luminescence, and isotopic and low-temperature thermochronological methods, and encouraging use of existing community laboratories and research that apply these tools to new minerals Coordinated community development of fully coupled climate—tectonic, geochemical, ecological—surface process models that engages existing numerical modeling initiatives and organizes interdisciplinary workshops to include atmospheric, ecological, and paleontological disciplines Development and support of shared, community experimental laboratory facilities for landscape research across time scales and testing of models in a controlled environment The primary science objectives for this initiative include the following: Improving methods for quantitative reconstruction of past Earth surface states from the record of landforms, paleobotany, geochemistry, paleo-soils, and sedimentary deposits Developing detailed paleoclimate, tectonic, and sedimentary records of abrupt changes in Earth surface processes and of landscape resilience over long time scales to understand the tolerable limits of stochastic variability within different geomorphic systems Developing and testing quantitative predictive models for the Earth surface system across time scales with focus areas that include using realistic crust and mantle rheologies; coupling to mantle convection; modeling glacial erosion and transport; and coupling to biogeochemical cycles
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface Developing and improving technical capabilities and data collection in near-surface geophysical methods to image and measure Earth’s near-surface structure and physical properties in three dimensions Coevolution of Ecosystems and Landscapes With new ways of measuring how the living and the nonliving surfaces coorganize and an increasing ability to link biotic processes and landscape evolution, the opportunity exists to forge a new understanding of the coevolution of ecosystems and landscapes (Box S.4) and to address pressing problems of future environmental change. This initiative could lead to the transfer of concepts and theories on physical systems to ecological research and to the use of ecological principles to guide coupled ecosystem and landscape modeling. A primary goal is to build the capability to predict future coupled ecosystem and landscape states under varying climate and land-use conditions. BOX S.4 Potential Implementation Mechanisms: Coevolution of Ecosystems and Landscapes This initiative emphasizes work at the interface of Earth and biological sciences. The ultimate goal is to create opportunities for discoveries that are equally advanced in the fields of ecology and Earth surface processes and are obtainable only with strong interdisciplinary interactions. Specific mechanisms to develop these collaborations include the following: Establishing working groups that organize regular meetings to focus on research at the interface of ecosystems and landscape processes and evolution and on opportunities for interdisciplinary teaching and formulating joint research plans—special sessions on ecosystems and landscapes at national meetings of many organizations are a start A community-level modeling program for ecologists and Earth scientists to collaborate on models for short-term forecasts and long time-scale predictions of the coevolution of ecosystems and landscapes Joint field campaigns conducted by ecologists and Earth surface scientists, including climate scientists, geomorphologists, and hydrologists, to help identify and quantify underlying mechanisms that link biota, ecosystems, and Earth surface processes Employing the network of observatory sites to explore ecological and Earth surface processes Co-development of instrumentation, geochemical, and geochronological tools that could facilitate significant advances
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface The primary science objectives for this initiative include the following: Improvement of theory and observations that relate spatial patterns and dynamics of biota to landscape setting (topography, hydrology, and geology) for given climatic conditions Development of models that incorporate both the geomorphic transport laws and the requisite biogeochemical equations to account mechanistically for the role of biota Development of landscape evolution theory that includes the effects of biota (and its possible coevolution with landscape) Development of models to predict the coevolution of climate, biota, and landscape processes under a scenario of increased greenhouse gases Development of observations and models for the interaction of biota with stream channel and floodplain morphology and dynamics Future of Landscapes in the “Anthropocene” Substantial advances have been made in understanding the range and extent of human impacts on Earth surface systems. These advances, coupled with technological breakthroughs, present opportunities to provide answers to a fundamental and urgent question: How can we understand, predict, and respond to rapidly changing landscapes that are increasingly altered by humans? The overarching goal of this initiative is to transform our understanding of integrated human-landscape systems and our ability to predict how they might evolve in the future (Box S.5). The primary science objectives for this initiative include the following: Improved understanding of the long-term legacies of human impacts on landscapes and quantification of current rates of impacts, especially in environments that are sensitive to global climate change Development of mechanistic models linking multiple and cumulative effects of human activity Development of integrated models of the complex interactions within human-dominated landscapes, incorporating decision making and human behavior Greater understanding and predictive capacity for coupled human-landscape dynamics Capacity building to anticipate and guide options for mitigating, reversing, and adapting to human-caused landscape change Coordinated collection and database management of sociological and geographical information on land use for incorporation into quantitative models
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface BOX S.5 Potential Implementation Mechanisms: Future of Landscapes in the “Anthropocene” Developing and advancing this initiative require new collaborations among Earth surface scientists and a range of social and behavioral scientists—including economists, political scientists, sociologists, and human geographers—to incorporate decision making and human perception and behavior in quantitative models. Collaboration with geospatial scientists is further needed to integrate geospatial technologies into modeling and field-based efforts, as is collaboration with engineers and applied practitioners to use manipulated landscapes for experimentation. Increased collaboration among Earth surface scientists, ecologists, and climate scientists, among others, is also needed to investigate the interacting processes within human-dominated landscapes. These collaborations could be advanced through: Workshops for Earth surface scientists and social scientists to build integrated community approaches, research questions, methodologies, scales of inquiry, and theories for human-landscape systems Workshops for geospatial scientists and Earth surface scientists to examine the integration of geospatial technologies with experimental, modeling, and field approaches and to process and synthesize remote-sensing data Development of community field and modeling centers to acquire the data necessary for new integrative and predictive models that involve multiple stressors within human-dominated landscapes, including social processes that influence those interactions Focused field studies in sensitive environments vulnerable to anthropogenic and climate change, including coastal and urban areas, mountain and polar environments, and arid and semiarid areas—existing environmental observatories could be employed Collaborative research using engineered landscapes and restoration and redesign projects. These relatively controlled research conditions can improve fundamental knowledge of processes relevant to a range of environments and problems. This collaboration could involve engineers and applied practitioners working with Earth surface scientists Use of restoration and redesign projects to test hypotheses about how to build self-maintaining ecogeomorphic systems S.4 CONCLUDING REMARKS Earth’s surface is the only habitat available to humans, and understanding the processes by which that habitat has been created and the ways in which it changes is important to determining the causes of environmental degradation, to restoring what is degraded, and to guiding decisions toward a sustainable future. We have the technological ability to monitor closely the response of landscapes to climate change and human activities, as well as to interactions with other Earth surface processes. The need to model all of
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Landscapes on the Edge: New Horizons for Research on Earth’s Surface these interactions in a predictive fashion is clear. To develop this capability, fundamental research is needed to understand the process-based linkages among life, climate, tectonics, human activity, and landscapes. Environmental restoration and design requires thoughtful consideration of Earth surface processes, landscape history, and the interactions between human activities and surface processes. This area is of great consequence for contributions from scientists in the integrative, emerging field of Earth surface processes that lies at the intersection of natural science disciplines in Earth, life, atmospheric, ocean, and social sciences. With the rise of new scientific questions relating various components of the Earth system, new opportunities and tools for research, rapid growth of human population, and unprecedented changes in biota, land cover, process rates, and global climate, an appraisal of the study of Earth surface processes is timely and crucial.