The Effects of Climate Change on Forest Resources

The Environmental and Energy Study Institute (EESI) held a briefing about the likely effects that global climate change will have on the structure, function, and ecological dynamics of forest ecosystems in the United States. As Congress discusses climate change policies and legislation, it is important to develop a better understanding of these impacts.

Changes in average annual temperature, precipitation, length and timing of the growing seasons, and other climate-related factors can result in a number of both short- and long-term changes to forests, including altered growth rates, changes in stand structure and dynamics, and shifts in geographic distribution of both individual tree species and forest types. In addition to these direct effects, climate change has the potential to indirectly change the structure and dynamics of the entire forest ecosystem by affecting insect infestations, wildfire patterns, and other key processes and components of forested landscapes. In 2005, mortality due to mountain pine beetle (Dendroctonus ponderosae) alone affected over 3 million acres, and this number is rapidly increasing over a significant portion of the intermountain West. Recent studies have tied both increases in catastrophic wildfires and the rapid expansion of bark beetle infestations to climate change. These changes will have dramatic and far-reaching effects on biodiversity, ecosystem functioning, water management, and recreation and tourism, as well as the multi-billion dollar forest products industry in the United States.

This briefing was part of an EESI initiative focusing on sustainable forest bioenergy. To adequately assess the role that forests can play in addressing climate change, it is critical that we first have a firm understanding of the effects that climate change will have on forests. Biomass assessments and carbon sequestration formulae that pre-suppose static forest dynamics and processes will inevitably result in unreliable conclusions. As one of the key elements of the global carbon cycle, it is essential that the dynamic interaction between forests and climate must be taken into account when discussing bioenergy, carbon sequestration, afforestation or other forest-based solutions to climate change.