Summary

The research of the last decade has demonstrated that ecosystems and human systems are influenced by multiple factors, including climate, land use, and the by-products of resource use. Understanding the net impact of a suite of simultaneously occurring environmental modifications is essential for developing effective response strategies. This suite of simultaneous influences, or multiple environmental stresses, produces more than simply additive impacts. The term means that there is a confluence and interaction of stresses that both accumulate and, because of feedbacks, increase or become more complex. Multiple environmental stresses in composite lead to qualitatively and quantitatively different outcomes from single influences, and thus research that seeks to better understand these multiple stresses requires thinking differently from that used in traditional, sectoral, or single-problem approaches.

There are no generally agreed upon methodologies for studying complex systems of interconnected environmental influences that can have different impacts in varied and sometimes subtle directions. Understanding multiple stresses almost always requires consideration of multiple variables, nonlinear processes, and a variety of spatial and temporal scales. We typically have only a rudimentary understanding of the dynamics of interactions between different environmental variables in complex systems, making it extremely difficult to predict the combined effects of multiple interacting stresses. In addition to gaps in the scientific understanding of multiple environmental stresses, there is a lack of understanding of how to move from understanding to management and policy decisions, and in particular how to devise options that make sense in the face of significant uncertainties.



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Understanding Multiple Environmental Stresses: Report of a Workshop Summary The research of the last decade has demonstrated that ecosystems and human systems are influenced by multiple factors, including climate, land use, and the by-products of resource use. Understanding the net impact of a suite of simultaneously occurring environmental modifications is essential for developing effective response strategies. This suite of simultaneous influences, or multiple environmental stresses, produces more than simply additive impacts. The term means that there is a confluence and interaction of stresses that both accumulate and, because of feedbacks, increase or become more complex. Multiple environmental stresses in composite lead to qualitatively and quantitatively different outcomes from single influences, and thus research that seeks to better understand these multiple stresses requires thinking differently from that used in traditional, sectoral, or single-problem approaches. There are no generally agreed upon methodologies for studying complex systems of interconnected environmental influences that can have different impacts in varied and sometimes subtle directions. Understanding multiple stresses almost always requires consideration of multiple variables, nonlinear processes, and a variety of spatial and temporal scales. We typically have only a rudimentary understanding of the dynamics of interactions between different environmental variables in complex systems, making it extremely difficult to predict the combined effects of multiple interacting stresses. In addition to gaps in the scientific understanding of multiple environmental stresses, there is a lack of understanding of how to move from understanding to management and policy decisions, and in particular how to devise options that make sense in the face of significant uncertainties.

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Understanding Multiple Environmental Stresses: Report of a Workshop The concept of multiple environmental stresses taken alone can seem vague, and thus the steering committee organized this workshop around two examples to provide different perspectives on multiple stress scenarios. The first case selected was drought, a complex environmental condition that both is driven by multiple environmental stresses and leads to multiple stresses across a wide range of time and spatial scales. Drought is a normal climate variation that can vary in magnitude and intensity, and it provides a clear illustration of the feedbacks involved both in the occurrence of the natural event and in the human activities that may alter societal vulnerability (e.g., population growth, water management policies, and changes in land cover). The second case selected focused on a wide range of atmosphere-ecosystem interactions that taken together reflect characteristics of multiple, simultaneous environmental stresses. These two cases were selected because they offer very different problems, scales, and lessons. Because of this, the presentations and discussions—and the respective chapters in this report—are not perfectly parallel. Despite the differences in approach, the workshop participants did identify some important commonalities. As discussed in Chapter 4, the overarching lesson of the workshop is that society will require new and improved strategies for coping with multiple stresses and their impacts on natural and socioeconomic systems. Improved communication among stakeholders, increased observations (especially at regional scales), improved model and information systems, and increased infrastructure to provide better environmental monitoring, vulnerability assessment, and response analysis are all important parts of moving toward better understanding of and response to multiple-stresses situations. Workshop participants identified the development of comprehensive regional frameworks for conducting environmental studies as a key part of understanding multiple environmental stresses: An integrated regional web of sensors that links existing observations into a coherent framework 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 Complex coupled system models at the spatial and temporal scales appropriate to study specific and integrated biologic, hydrologic, and socioeconomic systems A strong connection to significant regional issues and stakeholders. Workshop participants identified the Regional Integrated Sciences and Assessments program (RISA) as a possible model for such regional frameworks. Overall, the degree to which progress is made on complicated environmental problems is proportional to the degree we are able to implement these five

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Understanding Multiple Environmental Stresses: Report of a Workshop organizing principles, and progress will be limited if we cannot. This will take a major reorganization in how we approach multifactor environmental problems and thus will be difficult. As an outcome of the workshop, seven near-term opportunities for research and infrastructure that could help advance our understanding of multiple stresses and make this understanding useful to decision makers were proposed. These are discussed in more detail in Chapter 4. Building a new U.S. ground-based ecological measurement network to understand multiple stresses at multiple scales Enhancing global information systems and satellite observations Synthesizing existing data to identify status and trends in ecosystems Analyzing extreme events of record to identify nonlinearities and thresholds for future change Identifying technologies, management, or institutional mechanisms to enhance resilience Developing regional foci to understand vulnerability and coping capacity in particular places Increasing stakeholder involvement to help identify problems and solutions and provide ideas on the kinds of information needed (and in what format) to be useful for decision making.

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