Natural and Human-induced Disturbances and Their Impacts on Forest Carbon Budgets in North America

Abstract:

Natural and human-induced disturbances have profound impacts on forest carbon dynamics, and may cause the greatest uncertainty in estimating forest carbon budgets. In North America, three countries show very different forest disturbance patterns: Canadian forests are dominated by natural disturbances such as wildfires and insect outbreaks; forests of Mexico are more affected by human-induced land disturbances such as land-use change; while US forests are equally affected by human-induced and natural disturbances. As human-induced disturbances are closely linked to socioeconomic factors, natural disturbances are usually viewed as a natural process in forests and have equilibrium impacts on forests over the long run. However, with climate change and related changes in natural disturbance regimes in terms of frequency, intensity and scale, there are now fundamental changes in the nature of the impact of natural disturbances on forest carbon dynamics and even greater uncertainty about forest carbon budgets and feedbacks to the atmosphere and climate. In this study, we synthesize disturbance information for North America based on existing remote-sensing products, ground-based observations and modeling studies, evaluating impacts of disturbances on forest carbon budgets that are relevant to disturbance types, scales, frequency and intensity. The work represents the initial step of a more ambitious project tackling this research challenge for North America that crosses a broad climate gradient and diverse socioeconomic entities. The goal is to ultimately improve the estimates of forest carbon budgets and their potential for climate mitigation under changing environments.