The current distribution of forest typeswas largely established at the beginning of the Holocene epoch (approximately 12,000 BCE), but forests are constantly in flux. Many regional scale stresses (e.g., drought, heat, fire, and insect) and even a few multi-regional or global stresses (e.g., 8200 BCE cooling, or the medievalwarming period) have occurred over the past 12 millennia. However, modern ecology is less than 200 years old, and large-scale anthropogenic impacts on climate are mainly confined to the latter half of the 20th century. Given the large number of potential climate, geographic, demographic combinations, and relatively short time of study, we should not be surprised that there are an increasing number of observed environmental stresses with no antecedent point of reference. Chronic anthropogenic stressors (e.g., elevated nitrogen, sulfur and heavy metal deposition, and tropospheric ozone) have mentality precondition human thought to accept these impacts as part of the environmental condition in the areas in which they occur. Therefore, the acceptance of non-antecedent variability is part of the challenge associatedwith climate change in which variability exceeds historic observation. This desensitizing of human reaction to disturbance impedes societies' ability to acknowledge unprecedented environmental change, and thereby delays measures to reduce or adapt to these non-antecedent stresses. A poor understanding of non-antecedent stress also contributes to the challenges of addressing these unprecedented disturbances.
McNulty, Steven; Du, Enzai; Paoletti, Elena. 2017.Virtual special issuep preface: Forest response to environmental stress: Impacts and adaptation. Science of The Total Environment. 607-608: 647-648. 2 p. http://dx.doi.org/10.1016/j.scitotenv.2017.06.204