October 26, 2009

Tools for the Carbon Economy

fall_treesBy Jonathan Dandois
Will the census of the future ask homeowners how many trees they have on their property?

With humanity now faced with a changing climate under even the most stringent efforts to reduce carbon emissions, carbon accounting has become a hot topic for scientists, politicians and economists. While carbon accounting at the scale of individual households and their landholdings is unlikely in the near future, nations and regions need efficient methods to determine how much carbon is held and released within their borders- and this applies even more to the monitoring of projects to store carbon by means of tree plantings and deforestation reduction (e.g.. REDD). Accurate and regularly updated measures of carbon sources and sinks are critical to effective global governance of carbon emissions and climate change.

You will not see the Carnegie Airborne Observatory (CAO) flying around your neighborhood in the U.S. this year, but Greg Asner and his team are using the latest remote sensing technology to measure carbon stored in the world’s tropical forests. Asner’s carbon measurement tools and their importance in managing carbon stored at local, regional and global scales were the subject of a recent news feature in Nature in the lead up to the global climate talks in Copenhagen in December (Tollefson 2009). I read this short piece and immediately thought- ”I like this! I want to help!” Here I briefly share with you why I found this piece compelling and encouraging in the context of my own research.

Forests are both sources and sinks of carbon that require measurement and understanding both at the broad spatial scales of entire forests and at the fine spatial scales of the trees they are composed of. Accurate measurements of carbon in forest biomass, composed of both the above and belowground parts of trees, requires extremely time and labor intensive field campaigns to measure the size, numbers and types of trees within a forest. Over the past 30+ years, advances in remote sensing technologies have facilitated more and more accurate measurements of forest biomass and other characteristics from both aerial and space-based platforms.

The state-of-the-art of such techniques, and the focus of Asner’s research, involves a combination of super-accurate GPS and high powered laser scanning (LiDAR; Light Detection and Ranging), together with optical cameras that can detect light beyond the spectrum of human vision. This fusion of very high resolution LiDAR and optical cameras allows Asner and his team to measure forest canopy structure (height, density and volume) and estimate key forest parameters like biomass and total carbon. The spectral information collected by the optical cameras can also be used to distinguish and map the different species of trees in both the forest canopy and the understory vegetation beneath. Repeated collections of such data allow measurements and understanding of changes in forest biomass, biodiversity and other ecological parameters caused by natural and anthropogenic change processes- these insights will be essential to assist local and regional planners charged with keeping track of carbon for global climate change initiatives.

While the CAO provides detailed information for initial surveys of forest and carbon resources, local managers may require additional tools to monitor changes in carbon and to enforce forest policies. For example, the CLASlite system that Asner is giving to managers and governments (Nature feature), uses readily-available Landsat satellite imagery to make regular assessments of forest biomass- a big help with planning and enforcement strategies.

Like many of the changes that come with a changing climate, the idea of carbon policing is new and we have yet to see how best to implement carbon emissions reductions policies. Recent research published in PNAS suggests that decentralizing forest carbon management- putting local communities in charge of the ‘forest commons’ may be a very useful strategy for implementing forest carbon policies, though the authors offer that more and better data is needed for more concrete conclusions (Chhatre 2009).

Whether it is local communities, national governments, or a carbon police force in charge of managing carbon, new tools will be needed to provide cheap and accurate forest biomass measurements on demand. Once forests have been fully measured and mapped, managers usually need only regular sampling to measure carbon changes, perhaps only at sites with changes identified by CLASlite or another rapid regional assessment system.

This opportunity excites us, as we are currently working on an inexpensive scanning system that can measure forest biomass across landscapes, much like LiDAR or CAO, though restricted to measurements of landscape samples, rather than entire regions. This system uses a combination of consumer-grade digital cameras, hobbyist aerial platforms, and computer vision technology. While still in its infancy, the system has shown great promise for accurately measuring tree height, the first step in remotely measuring biomass, in a platform that costs under $1000! It is our sincere hope that our research can help provide a key tool for the new carbon economy by providing local researchers and even local communities around the world with remote sensing tools that they can use to manage carbon on their own.

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