Land-use Change and Biophysical Accounting in Forest Carbon Projects

Abstract:

Biological carbon sequestration by reforestation and afforestation is being promoted as an opportunity to help mitigate global warming and climate change. The scientific basis to support such forestry activities is shifting to include many biophysical dimensions beyond carbon storage. In this talk I address two questions: 1) Where can forests help slow the buildup of greenhouse gases in the atmosphere while also providing beneficial biophysical feedbacks? and (2) How many extra resources, including water and nutrients, may be needed to achieve this carbon storage and climate benefit? By comparing the biophysical forcings and climatic impact of vegetation replacement across North America using satellite-derived albedo, land surface temperature (LST), and evapotranspiration (ET) between adjacent vegetation types, we show that a carbon-centric accounting is, in most cases, insufficient for climate mitigation policies. Where afforestation or reforestation occurs, deciduous broadleaf trees are likely to produce stronger cooling benefits than evergreen needleleaf trees provide in temperate ecosystems. Our analyses also suggest that forestry activities will have the most climatic benefits at locations where background albedo prior to landscape change is low, snow cover is minimal, cloud cover is high, and soil water availability is ample.