Climate change and forest disturbances

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Studies of the effects of climate change on forests have focused on the ability of species to tolerate temperature and moisture changes and to disperse, but they have ignored the effects of disturbances caused by climate change. Yet modeling studies indicate the importance of climate effects on disturbance regimes. Local, regional, and global changes in temperature and precipitation can influence the occurrence, timing, frequency, duration, extent, and intensity of disturbances. Because trees can survive from decades to centuries and take years to become established, climate-change impacts are expressed in forests, in part, through alterations in disturbance regimes. Disturbances, both human-induced and natural, shape forest systems by influencing their composition, structure, and functional processes. Within the United States, natural disturbances having the greatest effects on forests include fire, drought, introduced species, insect and pathogen outbreaks, hurricanes, windstorms, ice storms, and landslides. Each disturbance affects forests differently. Some cause large-scale tree mortality, whereas others affect community structure and organization without causing massive mortality (e.g., ground fires). Forest disturbances influence how much carbon is stored in trees or dead wood. All these natural disturbances interact with human-induced effects on the environment, such as air pollution and land-use change resulting from resource extraction, agriculture, urban and suburban expansion, and recreation. Each disturbance has both social and economic effects. Estimating the costs of each of these disturbances is very difficult. Of the eight forest disturbances considered in this article, ice storms are the least costly, averaging about $10 million and more than 180,000 ha annually; and insects and pathogens are the most expensive, with costs exceeding $2 billion and 20.4 million ha per year. The socioeconomic aspects of these damages are only part of the cost. Costs of impacts to ecological services (e.g., water purification) can be large and long term. This article examines how eight disturbances influence forest structure, composition, and function and how climate change may influence the severity, frequency, and magnitude of disturbances to forests. Examples are focused on the United States, although these influences occur worldwide. Also considered are options for coping with disturbance under changing climate. This analysis points to specific research needs that should improve the understanding of how climate change affects forest disturbances. As a consequence of climate change, forests may soon face rapid alterations in the timing, intensity, frequency, and extent of disturbances. The number and complexity of climate variables related to forest disturbance make integrated research an awesome challenge. Even if changes cannot always be predicted, it is important to consider ways in which impacts to forest systems can be mitigated under likely changes in disturbance regimes. The task for the next decade is to understand better how climate affects disturbances and how forests respond to them. Improved monitoring programs and analytic tools are needed to develop this understanding. Ultimately, this knowledge should lead to better ways to predict and cope with disturbance-induced changes in forests.

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ELECTRONIC FILE - Zoology: Multiple Species; ELECTRONIC FILE - Ecology

SWAP (2/19/2016) citation:
Dale VH, Joyce LA, McNulty S, Neilson RP, Ayres MP, Flannigan MD, Hanson PJ, Irland LC, Lugo AE, Peterson CJ, et al. 2001. Climate change and forest disturbances. [accessed 2015 Nov 19]; Bioscience. 51(9):723–734. http://flux.aos.wisc.edu/~adesai/documents/macrosys_papers-ankur/disturb....