The goal of this project is to document pan-arctic changes in large-scale disturbances (thermokarst, fire, insect outbreaks, and forest harvest), relate these to climatic and social change, and to assess their ecological, climatic, and societal consequences in high-latitude ecosystems (tundra and boreal forest). Recent trends suggest that continued high-latitude warming will likely be accompanied by increases in disturbances such as fire, insect outbreaks, thermokarst, and potentially forest harvest and land-cover conversion to grassland or agriculture. These disturbances have qualitatively different effects on the climate system, ecological processes, and therefore society than do those ecological processes that are more continuous functions of climatic change. Large-scale disturbances have the practical advantage that they can be quantified regionally by remote sensing so processes studied locally are more readily extrapolated to large scales. The program builds on existing research programs in Alaska, Canada, Scandinavia, and Russia and on global remote-sensing and inventory programs. We choose a pan-arctic scale so we can relate our results to the functioning of arctic climate system and take advantage of geographic variation in climate and disturbance regime. We also build from national and site-based research programs and databases, providing the opportunity to link processes and local, regional, and global scales. We address the following questions: 1. How have changes in climate affected disturbance regime across the arctic and boreal zones, and how have these changes in disturbance affected climate through changes in trace gas emissions, smoke, and energy exchange? Do feedbacks from land-surface processes to climate buffer or amplify the initial climate trends? In other words, what is the net effect of these high-latitude climate feedbacks on the global climate system? We currently have circumboreal databases of disturbances (fire, insects, and forest harvest), vegetation, climate (1900-2005; projected to 2100), and date of snowmelt, providing the datasets necessary to make preliminary estimates of high-latitude climate feedbacks. National programs will refine and improve these databases and develop climatic, geographic, and socioeconomic correlations as a basis for developing rules to estimate future disturbance rates. 2. How do changes in disturbance regime affect post-disturbance ecosystem development and future disturbance probability? Are there thresholds in disturbance severity or size that trigger qualitatively different patterns of ecosystem development? For example, are there conditions where fire at treeline or insect outbreaks at the southern margin of the boreal forest lead to a permanent land-cover transition? We will rely on regional studies to develop simple models of post-disturbance succession for fire, logging, insects, and agriculture. We are particularly interested in circumstances that trigger radically different vegetation succession such as wet tundra to shrub tundra; tundra to forest; conifer to deciduous forest; or forest to grassland. Based on preliminary studies, we are confident we can develop these models. 3. How have changes in disturbance regime and resulting changes in ecosystem structure and functioning affected ecosystem services on which society depends, and how have human activities (ignitions, suppression, and land-cover change) influenced the response of disturbance regime to climatic change? Many ecosystem services (timber, fuelwood, berries, moose, caribou, etc.) can be estimated from the interactive effects of climate and vegetation (stand type and age). Based on maps of climate and vegetation (#1) and disturbance frequency and successional trajectory (#2), we can estimate temporal and spatial patterns of ecosystem services. Based on local and regional studies we can estimate the validity of these estimates and the extent to which they are influenced by other factors such as human harvest. We will then explore the social, economic and cultural bases for these human impacts on ecosystem services. 4. How have policies changed in response to recent changes in climate and disturbance regime, and what factors influence the rigidity or flexibility of these policies and therefore the potential for adaptation or vulnerability at times of rapid change? Based on the patterns described above we will develop alternative scenarios of future ecosystem services (climate feedbacks and subsistence resources). We will explore with residents and policy makers policies that might influence the relative likelihood of these alternative scenarios. Summary provided by http://classic.ipy.org/development/eoi/proposal-details.php?id=275
POLAR DISTURBANCE AND ECOSYSTEM
P - R