Monitoring carbon stocks in the tropics and the remote sensing operational limitations: from local to regional projects.

Current remote sensing technologies are effective tools for contributing to the estimation of terrestrial carbon stocks and carbon stock changes. This paper provides an overview of information requirements, sensor capabilities and limitations, and analysis approaches for the use of remotely sensed data in the generation of tropical carbon sequestration monitoring systems. While it is evident that remotely sensed data have tremendous utility for monitoring carbon stock changes, it is important to be aware of their limitations. Three critical limitations are: (1) the definition of methods and algorithms to accurately estimate forest age, (2) the provision of techniques that can yield accurate estimation of deforestation rates in both tropical dry and wet forest environments, and (3) the strong need to develop new approaches to link biophysical variables (e.g., leaf area index) to spectral reflectance to support spatially distributed carbon sequestration models. The validity of final estimates of carbon and carbon stock changes rests on complex issues at several levels, from the data themselves, to the analysis, interpretation, and validation of the data. Consideration of these issues, as well as the need for sound project planning and development within budget constraints, will be important in the development of carbon stock monitoring programs in the tropics.