Our Understanding Today
Despite the economic and environmental significance of forests, we have only imprecise measurements of the physical variables that determine their valued attributes, whether for timber, carbon management, habitat, or other purposes. Experts agree that we poorly measure deforestation of tropical forests and devote even less attention to reforestation and forest preservation occurring in boreal and temperate forests. Yet nations may be on the verge of incorporating forests into complex and costly climate policies for managing carbon on a foundation of shaky forest inventories. Today, the trading of carbon credits on the European Climate Exchange, the World Bank’s recent initiative for a Forest Carbon Partnership Facility, and other major developments impart earnestness and require auditable measurement, adding urgency to that required for environmental warnings of the past.
The imprecision in forest measurement is a consequence of many problems, including nonstandard reporting methodologies and a patchwork of substandard tools and techniques. Nations self-report these data, differ in the political and fiscal priority given to accurate assessment, and vary widely in technical capability to inventory their forests. Data are updated only every five years or so and even then are often extrapolated from past trends.
New global satellite measurement and monitoring capabilities hold promise as a means of significantly improving measurements by providing the basis for an accurate, periodic, and cost-effective global forest “census.” Use of satellite technology has some shortcomings and risk, but the unique advantages include the potential for improvement in temporal and spatial resolution, standardized measurement protocols, regularly updated global observations, and transparent, replicable methodology. Yet few forest inventories incorporate satellite-based measurement. Advancing a state-of-the-art forest census requires a much stronger network of expertise and an international coordinating framework to organize the collection of measurements.
Our Efforts
Under the generosity of the Alfred P. Sloan Foundation, we have undertaken a one-year project to design and advance a framework for improved measurement and monitoring. We base this framework on the four critical and integral attributes of forests—area, timber volume, biomass, and carbon—and assess the advantages and limits of existing and near-term measurement technologies, including satellite observations, to measure these variables. To carry out this project, we have assembled a team of recognized experts in forestry and in satellite and in situ observations, and representatives of international organizations. Importantly, we will gather advice to learn the accuracy needed by those who would use these measurements, including national governments, private corporations, nongovernmental organizations, and in anticipation of a market for forest carbon, public and private lending agencies and investors who are likely market participants.
The outcome of our project will be a framework for effective global forest measurements and the first steps toward the development of an international network of people and institutions to evolve its implementation. We see this outcome as a necessary and even urgent action to provide information fundamental to managing competing demands on the world’s forests, providing accurate estimates of forest resources for the public and for decisionmakers, and serving as the basis for a forest carbon market.
Examples of Measurement Discrepancies (from Waggoner, 2009)
Table 3
Comparisons of six IPCC Tier 1 and IPCC Good Practice measurements of carbon density Units of t tons C/ha equal Mg carbon/ha. Tier 1 estimated by forest type and continent. Source: Brown et al. (2007) box 4.2.
Figure 1
Forest cover from Mexico to Panama classified by GLC2000 and by MODIS (lower panels) and the disagreement between them. The red circle identifies a hot spot of disagreement in Guatemala and El Salvador. Source: Geo-WIKI 2009.
