NCASI publications summarize results from studies of historical and projected forest growth response to climate factors

Forest ecosystems are a source of wood and fiber, clean water, recreational opportunities, habitat for wildlife, and other ecosystem services. Over the past century, various studies have reported changes in environmental factors such as CO2 concentrations, temperature, and precipitation, and in factors such as ozone, nitrogen deposition, and other pollutants. Changes in factors such as these have implications for forest ecosystems and the services derived from them.

Forest certification standards ask their participants to consider the potential for climate factors to affect forest growth, estimates of forest inventory, and planned harvests. Thus, NCASI recently published two reports, Technical Bulletin No. 1045 and Technical Bulletin No. 1046, summarizing results from studies of forest response to past and projected changes in climate factors.

For Technical Bulletin No. 1045, the author identified 62 publications that quantified historical forest growth trends in the US or Canada over periods ranging from 10 years to 300+ years. Reviewed papers used multiple sources of data, including remote sensing, permanent plots, growth models, tree ring analysis, and historical photography, to evaluate forest growth trends.  

The net conclusion from the reviewed studies is that, over the past century, forest growth has increased by over 40-60% in some cases. In some regions such as western Canada and Alaska, however, forest growth trends were mixed, with some forest types (e.g., aspen) experiencing dieback in certain locations due to recent droughts. Factors cited in the reviewed literature as causing enhanced growth varied by region, but included reduced fire frequency, rising CO2 concentrations, N deposition, warming temperatures, and changes in other environmental factors.

Technical Bulletin No. 1046 summarizes and evaluates current state of the art of model forecasts of forest growth responses to rising CO2 and hypothesized change in climate factors in North America, excluding Mexico, over coming decades. While it is difficult to make precise forest growth and yield predictions based on the publications examined, the reviewed results suggest increased forest growth in the regions where most commercial forestry takes place. This is so even when responses to the hotter global warming scenarios are simulated.

References 

National Council for Air and Stream Improvement, Inc. (NCASI). 2018. Forest growth trends in the United States and Canada. Technical Bulletin No. 1045. Cary, NC: National Council for Air and Stream Improvement, Inc. 

National Council for Air and Stream Improvement, Inc. (NCASI). 2018. Model-based forecasts of North American forest growth: A review. Technical Bulletin No. 1046. Cary, NC: National Council for Air and Stream Improvement, Inc.