National and international policies—such as the European Union's Renewable Energy Directive—increasingly seek to encourage sustainable use and conservation of "highly biodiverse grasslands." But to date, no global distribution map for all of the types of grasslands has been available to guide this work. NatureServe and the World Wildlife Fund collaborated to systematically define the term “grassland” in a way that it can be applied worldwide.
We then integrated the grassland types described in the International Vegetation Classification (IVC)—a global classification that characterizes all vegetation types—with the Terrestrial Ecoregions of the World (TEOW), a mapping system for the earth’s major regions of terrestrial biodiversity. Our scientific analysis had three key steps:
- Create a definition for the term “grassland” as a distinct biotic and ecological unit
- Use the division level of the IVC to classify each kind of grassland into major regional types
- Use the TEOW to report the distribution of each grassland type using ecologically-meaningful regional units
Through literature review, input from regional grassland experts, and consultation of geographic datasets, we identified ecoregions for which at least 10 percent of the area would historically have been comprised of grasslands (based on IVC division types). We then developed a catalog of IVC divisions by ecoregion, leading to a global biogeographic representation of earth’s grassland types and their distribution. As a result, we mapped 47 taxonomically distinct grassland divisions. Fourteen other grassland divisions described in the IVC could not be mapped with our approach due to their fine-scale distribution and limited spatial extent.
The framework developed by NatureServe and the World Wildlife Fund provides one of the first systematic, spatial overviews of the world’s grasslands, and sets the stage for more detailed classification and mapping at finer scales. Each regional grassland type can be characterized in terms of its range of biodiversity, thereby assisting in definitions of “highly biodiverse grasslands.” Thus, our approach of combining a vegetation classification with spatial ecoregions will be useful to international initiatives and policies which need clarity to advance sustainable use and conservation of grasslands.
- Dixon AP, Faber-Langendoen D, Josse C, Loucks CJ, Morrison J. 2014. Distribution mapping of world grassland types. Journal of Biogeography. doi: 10.1111/jbi.12381