This is Section 14.13 of the Arctic Climate Impact Assessment.
Lead Author: Glenn P. Juday; Contributing Authors: Valerie Barber, Paul Duffy, Hans Linderholm, Scott Rupp, Steve Sparrow, Eugene Vaganov, John Yarie; Consulting Authors: Edward Berg, Rosanne D’Arrigo, Olafur Eggertsson,V.V. Furyaev, Edward H. Hogg, Satu Huttunen, Gordon Jacoby, V.Ya. Kaplunov, Seppo Kellomaki, A.V. Kirdyanov, Carol E. Lewis, Sune Linder, M.M. Naurzbaev, F.I. Pleshikov, Ulf T. Runesson,Yu.V. Savva, O.V. Sidorova,V.D. Stakanov, N.M.Tchebakova, E.N.Valendik, E.F.Vedrova, Martin Wilmking.
This chapter focused mainly on annual crops and used GDD changes to estimate the likely effects of climate change on northern agricultural potential. Future assessments should include in-depth analyses of perennial crops and livestock, including scenarios of non-climate factors such as markets and public-sector policies. Better climate/crop models specific to agriculture in high-latitude regions (i.e., special crop varieties, long day-length effects) are also needed for future assessments. The effects of temperature increases and moisture changes on soil processes should be an integral part of the modeling systems. Future assessments should include many more climate stations in the boreal and arctic regions. The insect, disease, and weed issues that might accompany climate change and expanded agriculture should be addressed, particularly those with a unique high-latitude dimension unlikely to be part of ongoing studies in more southerly locations.
Given the critical role of public policy in agriculture in the region, an important issue is to identify national and international policies that might accommodate expansion of specific crops in the Arctic and subarctic. The infrastructure change needed to accommodate climate change should be identified along with the economic impacts of constructing new infrastructure and the economic impacts once such projects are constructed.
Boreal forests and climate change (14.13.2)
Given the large contribution of the boreal forest to the terrestrial carbon sink, and the large stocks of carbon stored in it, the health and vigor of the forests of this region are a particularly significant input to climate change policy, science, and management. Climatic models, recorded data, and proxies all indicate that there are significant spatial differences in temperature anomalies and associated tree growth changes around the globe. Not all species and relatively few forest site types have been examined to determine the strength and components of climate controls on tree growth. In order to determine the current and probable future carbon uptake of the boreal forest, these spatial differences in climate change and tree growth need to be systematically identified, both in the contemporary environment and in the recent historical past. Particular attention should be given to ways of effectively combining ground-level studies, which clarify mechanisms of control and provide a historical perspective, with remote-sensing approaches, which provide comprehensive spatial coverage that can be easily repeated and updated.
Trees and forest types that change their level of sensitivity to climate or even switch their growth responses to temperature are of particular interest. If climate controlled growth more at some times and less at other times in the past, tree-ring data used to reconstruct past climates will contain biases from the recorded climate data they are calibrated to, especially if the calibrating climate data cover a short time period. It is important to establish whether this change or reduction in tree growth–climate relationships is unique to the 20th century, whether the climate change of recent decades is largely responsible for growth declines, and finally, whether the mechanism of climate control is direct or indirect.
In order to better understand, measure, and project the rapid transformations that are possible in the boreal forest, better information is needed about the role of climate and forest condition in triggering major fire and insect disturbances. The specific characteristics of fires that result in maximum production of charcoal, which represents an important form of long-term carbon sequestration, are not well documented. Further insight is needed into the interaction of climate, forest disturbance, forest succession (and its influences on carbon dynamics), water and nitrogen dynamics, and changes in carbon stocks.
Forest advance into tundra has the potential to generate a large positive temperature feedback. Unfortunately, the understanding of change at this crucial ecological boundary comes from a small number of widely separated studies undertaken to achieve many different objectives. A coordinated, circumpolar treeline study and monitoring initiative will be necessary to address definitively the question of how and why this boundary is changing at the scale required to address its potential global importance.
Improvements in scaling output from GCM grid data to applications at a given location will improve confidence in scenario projections.
Boreal forests and ultraviolet-B radiation (14.13.1)
The UV-radiation survival strategies of evergreens appear to include simultaneous inhibition and avoidance. Late-winter and early-spring conditions are critical, and their importance should be studied further and effects quantified. More studies, longer-term studies, and well-designed ecosystem studies that incorporate the previously established effects from individual plot studies and consider the multiple influences of UV-B radiation on plant chemistry in settings of ecological communities will be needed to understand the cumulative effect of increased UV-B radiation levels on forests at high latitudes.
Chapter 14: Forests, Land Management, and Agriculture
14.2. The boreal forest: importance and relationship to climate
14.3. Land tenure and management in the boreal region
14.4. Use and evaluation of the ACIA scenarios
14.6. Tree rings and past climate
14.7. Direct climate effects on tree growth
14.8. Climate change and insects as a forest disturbance
14.9. Climate change and fire
14.10. Climate change in relation to carbon uptake and carbon storage
14.11. Climate change and forest distribution
14.12. Effects of ultraviolet-B on forest vegetation
14.13. Critical research needs