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Carbon counting in the USA - with a ground-breaking new biomass map

By Martin Leggett - 20 Apr 2011 16:0:0 GMT
Carbon counting in the USA - with a ground-breaking new biomass map

Image Credit: Woods Hole Research Center (www.whrc.org).

In many ways 'carbon-counting' - putting numbers to the flow of the carbon cycle in both the natural world and in man's activities - can be seen as the new accountancy of the ecological world. With the future of the planet being tied back in so many ways to man-made carbon emissions, getting those numbers right has become an essential task for scientists across the world. Now the US has its very own Domesday Book of carbon-counting - an incredibly detailed map of biomass, tree heights and above-ground carbon stocks that covers the hole of the lower 48 US States, which has been published today by the WHRC (Woods Hole Research Center)

After more than 5 years of toil, scientists from a diverse range of governmental and scientific bodies can finally unveil the National Biomass and Carbon Dataset (NBCD). This freely available dataset will allow users to dig down into the finer details of carbon and biomass distribution - which pinpoints forest and vegetation details to less than a 100 feet resolution. It is hoped that the breadth and scale of the information will provide an invaluable resource for those involved in everything from forest management and conservation, to land-use planning and climate change monitoring

The project to map the living 'green architecture' of the US was kick-started back in 2005 by NASA, as part of its Terrestrial Ecology Program. Building on NASA's Landsat satellite imagery, various government organizations helped to weave in information from land use, bio-ecological mapping and forestry inventory data sources. Pulling all these information pieces together allowed the scientists to create an accurate model of the height, thickness and types of vegetation - and so calculate the above ground carbon stored in plant materials - in every hectare of the US. That is something that has never before been available to researchers.

Dr. Wayne Walker, a WHRC scientist who worked on the project, explained, ''Maps of key forest attributes like canopy height and carbon stock have not existed for the U.S. at this level of spatial detail and consistency. They will provide ecologists and land managers with new and better information to support biodiversity conservation, wildfire risk assessment, and timber production while helping climate scientists and others to better understand the role that U.S. forests play in the global carbon cycle.''

It is hoped that this baseline will only be the start of efforts to track carbon in the USA - scientists associated with the project are already looking forward to expanding their work. Dr Josef Kellndorfer, project leader at the WHRC, said ''Naturally we are keen to produce the next generation data sets of this kind to assess in detail how carbon stock and forest structures are changing in this country, and internationally. We look forward to working with an ever growing community of colleagues in the U.S. and abroad on pushing the science of understanding the World's forests forward.''

(Image Caption: This map shows the first high-resolution (ca. hectare scale) map of aboveground live dry biomass and carbon stock for the conterminous United States. Sample postings are 30 meters and are spatially aligned with the National Land Cover Database 2001 published by the United States Geological Survey. The map was produced by integrating ca. year-2000, multi-sensor satellite imagery (Landsat ETM+ and Shuttle Radar Topography Mission data), bio- and geo-physical gradient data (elevation, slope, aspect, canopy density, and land cover), and USDA Forest Service Forest Inventory and Analysis field reference data. Empirical regression models were developed and applied in 66 ecoregional mapping zones. Final map assembly was performed by mosaicking the 66 zone-level biomass maps. The map shown here is accompanied by a map of predicted vegetation height, produced using a similar modeling approach and serving as a key input variable to the production of the biomass map. Aboveground woody carbon stock was estimated as 50 percent of the aboveground biomass predictions.)