Summary

The polar regions are experiencing rapid changes in climate. These changes are causing observable ecological impacts of various types and degrees of severity at all ecosystem levels, including society. Even larger changes and more significant impacts are anticipated. As species respond to changing environments over time, their interactions with the physical world and other organisms can also change. This chain of interactions can trigger cascades of impacts throughout entire ecosystems. Evaluating the interrelated physical, chemical, biological, and societal components of polar ecosystems is essential to understanding their vulnerability and resilience to climate forcing.

Although climate change is occurring on a global scale, ecological impacts are often specific, local, and vary from region to region. Because impacts in high latitude ecosystems are already evident and are expected to be even more pronounced in the future, polar regions offer novel opportunities to begin exploring interdisciplinary questions such as: How are marine and terrestrial species currently responding to the changing climate and can we explain and predict future changes and responses? How clearly can we attribute particular ecological impacts (e.g., species movement or changes in biogeochemical cycles) to particular climate forcings? Do we understand the role of various ecosystem feedbacks well enough to anticipate the extent of impacts? What do we know about the nature and probability of reaching certain thresholds or triggers where impacts change rapidly in scope or nature? What is the importance of change in remote polar ecosystems for the global environment and society at large?



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Summary T he polar regions are experiencing rapid changes in climate. These changes are causing observable ecological impacts of various types and degrees of severity at all ecosystem levels, including society. Even larger changes and more significant impacts are anticipated. As spe- cies respond to changing environments over time, their interactions with the physical world and other organisms can also change. This chain of interactions can trigger cascades of impacts throughout entire ecosystems. Evaluating the interrelated physical, chemical, biological, and societal components of polar ecosystems is essential to understanding their vul- nerability and resilience to climate forcing. Although climate change is occurring on a global scale, ecological impacts are often specific, local, and vary from region to region. Because impacts in high latitude ecosystems are already evident and are expected to be even more pronounced in the future, polar regions offer novel opportunities to begin exploring interdisciplinary questions such as: How are marine and terrestrial species currently responding to the changing climate and can we explain and predict future changes and responses? How clearly can we attribute particular ecological impacts (e.g., species movement or changes in biogeochemical cycles) to particular climate forcings? Do we understand the role of various ecosystem feedbacks well enough to anticipate the extent of impacts? What do we know about the nature and probability of reaching certain thresholds or triggers where impacts change rapidly in scope or nature? What is the importance of change in remote polar ecosystems for the global environment and society at large? 1

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2 FRONTIERS IN UNDERSTANDING CLIMATE CHANGE AND POLAR ECOSYSTEMS The Polar Research Board (PRB) of the National Research Council organized a workshop to address these issues on August 24-25, 2010, in Cambridge, Maryland. Experts gathered from a variety of disciplines with knowledge of both the Arctic and Antarctic regions. The workshop sought to bring together different people and perspectives and to use existing information to illustrate the nature of multidisciplinary linkages among ecosystem components under a changing climate regime. It also sought to generate conversation about how to better study and understand these changes in the future. Participants were challenged to consider what is currently known about climate change and polar ecosystems and to identify the next big questions in the field. A set of interdisciplinary “frontier questions” (dis- cussed in more detail in Chapter 2) emerged from the workshop discus- sions as important topics to be addressed in the coming decades: • ill a rapidly shrinking cryosphere tip polar ecosystems into new W states? • hat are the key polar ecosystem processes that will be the “first W responders” to climate forcing? • hat are the bi-directional gateways and feedbacks between the W poles and the global climate system? • ow is climate change altering biodiversity in polar regions and H what will be the regional and global impacts? • ow will increases in human activities intensify ecosystem impacts H in the polar regions? The first frontier question concerns the need to identify the impacts of the rapidly disappearing cryosphere on polar ecosystems. Workshop participants noted that the continued loss of cryosphere will be a major driver of change in polar ecosystems and will play a role in amplification of climate change and its teleconnections with lower latitudes. The topic of tipping elements and thresholds is a key issue for polar ecosystems as well. In some instances, critical thresholds may have already been reached or may soon be reached that could bring ecosystems to a new state or level of activity or behavior. If potential tipping points are known or can be anticipated, then responses to the changes may be identified. The second frontier question addresses the important processes that still need to be included in regional to global system models in order to characterize the response of polar ecosystems to climate forcing. Without these key elements the models cannot reliably predict future change. The third frontier question seeks to identify the key polar gateways (connec- tions and feedbacks) to the global climate system, a considerable challenge due to the vast complexities of the Earth’s climate and its interactions

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3 SUMMARY with natural ecosystems. Many workshop participants emphasized that improved understanding of such gateways will require collaborations between scientists with a broad range of expertise in many aspects of nat- ural systems. The fourth frontier question examines the various elements of biodiversity (genetic, taxonomic, and functional) and the effects of recent biodiversity loss in the polar regions resulting from anthropogenic changes in the environment and the climate system, as well as changes in human development. Finally, the fifth frontier question aims to determine the increasing ecosystem impacts and responses to human activities (e.g., fishing, tourism, and resource extraction) in the polar regions. To begin to address these questions, workshop participants discussed the need for a holistic, interdisciplinary systems approach to understand- ing polar ecosystem responses to climate change. As an outcome of the workshop, participants brainstormed methods and technologies (see Chapter 3) that are crucial to advance the understanding of polar ecosys- tems and to promote the next generation of polar research. These include new and emerging technologies, sustained long-term observations, data synthesis and management, and data dissemination and outreach.

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