Forests in Time is an edited volume of scientific studies and related essays that rely on observations made mainly at the Harvard Forest (established in 1907) near Petersham, Massachusetts over the past century. Delving further back into history using tools ranging from fossil records to personal journals, much of the book is dedicated to determining changes in the scientific characteristics of New England's forests over the past millennium. The research is empirically solid and pertinent to broader questions about climate change, land use, and natural and human-induced ecosystem evolution. The book is divided into five sections. The first three sections focus on the broader environmental impacts of human-induced change, and the latter explore detailed consequences of ecosystem change from natural events, including infrequent but severe hurricanes, on nutrients and nutrient cycling. The early chapters of the book are perhaps of greater immediate interest to the economist and economic historian, as they speak more directly to human-induced environmental impacts. The latter chapters may, however, in patient hands, help improve economists' ability to parse out characteristics of forests that generate value through ecosystem services and to design policy that more optimally matches scientific processes with economic values generated from these processes.

New England forests experienced human-induced change from Native American populations that was accelerated by European settlement 400 years ago. Both direct and indirect forces have influenced forest quality and quantity: the arrival of Europeans brought not only increased resource use but also new species, new pests, and new patterns of settlement that led first to extensive deforestation to make way for agriculture. This shift toward agricultural land uses reversed toward reforestation in the mid nineteenth century as agriculture in New England dwindled. The characteristics of this lengthy and sizable reforestation are one of the most interesting results of the book. The scientific evidence makes clear that the forests of today reveal strong residual impacts due to the human and natural-induced changes of years past, regardless of any initial visual similarities that may appear to exist. Several of these findings, such as the discovery of a long-term increase in nitrogen cycling on former agricultural lands and the roles of soil and atmospheric warming in the carbon cycle can help policy makers and scientists alike understand more completely the implications of human-induced changes ranging from logging to global warming.

The book highlights some useful distinctions for economic historians studying environmental impacts and change. Path dependency of environmental quality can be measured by several different sorts of scientific parameters, including soil nutrients, species composition, biomass, and nutrient cycling in soil and air. The scientific studies indicate that as human interventions and multiple uses of the forest over millennia have changed the structure and composition of the New England forest in visible as well as less direct ways. The forests are not in a long run steady state equilibrium; nor does restoration to a “pre-human” influence appear a feasible, or even possibly desirable, goal.

The Harvard Forest has conducted a number of experiments described in the book that highlight the complications of managing nature, even when we are attempting to manage it as nature would have done in the absence of human influence (such as prescribed burning to mimic natural fire disturbances, which has been a controversial goal of many public land managers in recent years). The reader may not absorb all the scientific details of phosphorus uptake, nitrogen fixing, or ecosystem respiration, but she should come to appreciate the ways in which long-run forest dynamics are inextricably entwined with human decisions regarding land use.

The book's insights into the evolution of species composition over time may prove most useful as we face increased disturbances from pests and invasive species that have already removed the American chestnut and elms as dominant species in our Eastern forests and now threaten the eastern hemlock significantly as well. Although the research may not provide solutions that allow these species to thrive, it may serve two other important roles: to enhance our scientific understanding of their ecology, giving us the information needed to create the best chances for survival; and to enhance our economic understanding of how the patterns of human resource use drive long-term ecosystem change so that future forests and their users might benefit from more knowledgeable decision making. The founders of the Harvard Forest had foresight, and the authors of these pages make admirable use of a unique and rich data source to provide today's decision makers with better information about our past impacts.