Climate change futures: health, ecological and economic dimensions

HEALTH AND ECOLOGICALIMPLICATIONSOutbreaks of the spruce bark beetle have causedextensive damage and mortality from Alaska toArizona and in every forest with substantial sprucestands (Holsten et al. 2000). The dead stands providesuperabundant kindling for lightning or human-inducedwildfires and are particularly vulnerable duringdrought. Wildfires are hazardous for wildlife, propertyand people, and they place demands on public healthand response systems. While some fires are naturaland can have positive effects on vegetation and insectbuildup, extensive, cataclysmic-scale wildfires poseimmediate threats to firefighters and homeowners, andparticles and chemicals from blazes and wind-carriedhazes cause heart and lung disease. Some fire byproducts(primarily from buildings) are carcinogenic.Hampshire. It is moving north with each warm winter.Those trees in Boston’s historic Arboretum, designed byFrederick Law Olmstead, have been drastically culledto try to control the infestation.Eastern Hemlock conifers play unique ecological roles.Hemlocks colonize poor soils and scramble to the crestsof mountains. Their arbors are umbrellas for resting deerin winter and the pine needles they shed nourish fish inthe deep forest streams they line. When stands ofHemlocks die, their needles add large amounts of nitrogento the streams and tributaries, and the impacts oftheir loss is under intense study (Orwig and Foster2000; Snyder et al. 2002; Ross et al. 2003).Figure 2.23 Hemlock Wooly Adelgid66 | NATURAL AND MANAGED SYSTEMSCASE STUDIESLosing forests to fire also threatens the ecological servicesthey provide: a sink for carbon dioxide, a source ofoxygen, catchments (“sponges”) for flood waters, stabilizersof soils, habitat for wildlife and, via extensivewatersheds, clean water. As sources of evaporanspiration(evaporation, and transpiration through leaves) andcloud formation, forests are integral to local climateregimes and to the global climate system. The resilienceof large areas of boreal spruce forests that have succumbedto beetle infestations, with resulting large-scalediebacks and fire, are not well understood.Figure 2.22 Spruce TreesDead stands of spruce trees infested with bark beetles.Image: Natural Resources Canada, Canadian Forest ServiceHemlock Wooly AdelgidWooly adelgid poses a risk to New England foreststoday. This aphid-like bug has already infected EasternHemlock trees in Connecticut, Rhode Island and,Massachusetts, and has moved into southern NewImage: Dr. Mark McClure, CT Agricultural Experiment StationECONOMIC DIMENSIONSAccording to the US Department of Agriculture ForestService (Holsten et al. 2000), more than 2.3 millionacres of spruce forests were infested in Alaska from1993 to 2000 and the infestation killed an estimated30 million trees per year at the peak of the outbreak.The Kenai Peninsula in Alaska, Anchorage’s playground,is a devastated forest zone. In Utah, thespruce beetle has infested more than 122,000 acresand killed over 3,000,000 spruce trees. The losseshave amounted to 333 million to 500 million boardfeet of spruce saw timber annually. Similar losses havebeen recorded in Montana, Idaho and Arizona, withestimates of over three billion board feet lost in Alaska,and the same in British Columbia.In British Columbia, nearly 22 million acres of Lodgepole pine have become infested — enough timber tobuild 3.3 million homes or supply the entire US housingmarket for two years (The Economist 9 Aug 2003).In the summer and fall of 2003 the wildfires cost morethan US $3 billion (Flam 2004). The loss of tree cover