Site: Harvard Forest LTER
David Kittredge.

We are living in times of rapid social and environmental change. Scientists and policy makers urgently require analyses of multiple interacting processes in order to anticipate and adapt to future global change. Understanding future environmental change will require new approaches to synthesizing ecological and social sciences. This is no easy task. The study of coupled human and natural systems is fraught with complex interactions, feedbacks, and time lags.

At Harvard Forest (HFR), research to understand the aggregate and interactive effects of climate and land-use change as they are superimposed onto naturally dynamic ecosystems is revealing the current and plausible future trajectories of regional forest change. This research has taken scientists off Harvard Forest property and into private woodlots throughout the state. In Massachusetts there are more than 200,000 private forestland owners; they are the front line of land-use decision making and they will largely determine the future condition of the forest. Their independent land use decisions represent a form of landscape disturbance, the cumulative effect of which can have long-lasting effects. Using the tools of social science, HF researchers have determined that private woodland owners are largely apathetic when it comes to professional advice and management of their land, and as a result often make reactive, uninformed decisions about its fate when exogenous circumstances (e.g., death, divorce, unanticipated expense) arise. Owners often rely instead on informal social networks for information and experience. These findings have been borne out and enhanced through analyses of more than 20 years of public records describing timber harvest and land use.

Spatially interactive landscape simulation models are now being used to integrate information about land owner tendencies with long-term ecological research at HFR, including 20 years of eddy flux measurements and permanent forest dynamics plots. In one example, HFR researchers conducted a landscape simulation experiment to evaluate regional forest change within the forests of Massachusetts over the next fifty years (2010 to 2060). Their objective was to estimate — assuming a linear continuation of recent trends — the relative influence of continued forest growth and recovery, climate change, forest conversion to developed uses, and timber harvest on above-ground forest carbon and tree species composition. They found that continued forest succession had the largest effect on total forest carbon, increasing stores by as much as seventy percent over the fifty-year period. Forest conversion and timber harvest reduced gains in forest carbon by 18 percent and four percent, respectively. Anticipated changes in temperature and precipitation had a positive effect on growth, increasing gains in carbon by 14 percent. There were few changes in species composition over the fifty-year simulation. Under the simplistic assumption that future land use patterns will resemble the recent past, they concluded that continued forest growth and recovery will be the dominant mechanism driving forest dynamics over the next fifty years, and that while climate change may enhance growth rates, this will be more than offset by land-use, primarily forest conversion to developed uses.

Graph for
State-wide average change in live aboveground biomass for each of the simulations used within a factorial experiment, which treated climate change (CC), forest conversion to developed uses (FC), and timber harvests (Harv) as treatments relative to a static climate (SC). Inset: Change in AGB from year 0 to year 50 for each scenario.
Thompson et al. 2011.