NatureServe and Partners Unveil Adaptable, Ecology-Based U.S. National Vegetation Classification

ARLINGTON, VA - NatureServe is proud to publicly launch the U.S. National Vegetation Classification (USNVC), a 20-year collaborative effort to devise a unified and consistent national reporting system for plant communities. The USNVC opens new avenues for broad-scale and long-term analyses of landscape change.

As a collaboration between NatureServe, the Ecological Society of America (ESA), and federal agencies, particularly the U.S. Forest Service and the U.S. Geological Survey, the USNVC is a reporting standard organized around ecological principles for the study of plant communities. It is the first classification of its kind designed to adapt to new ecological knowledge and expand to absorb new vegetation types. 

The organizing framework of the classification helps independent and federal scientists speak the same language, whether to monitor the high elevation red spruce forests of the Great Smoky Mountain National Park or conduct broad scale analyses of forest trends across the North American continent. 

Don Faber-Langendoen, Ph.D. is a senior research ecologist at NatureServe and editor-in-chief of the U.S. National Vegetation Classification. “We call it the eco-veg approach. The idea of the classification’s hierarchy is to reflect the functional ecology of plant communities,” said Faber-Langendoen. “The eight levels of the hierarchy are organized around ecological concepts at different scales and can be refined or expanded as new information emerges from ecological research.” 

The National Vegetation Classification provides a common rubric for reporting data about public lands, while allowing federal agencies to preserve their own classification systems through "cross walks." Vegetation types are best typified by collecting quantitative field plot data that record plant species, vegetation structure, and site factors. People from a great diversity of environmental sectors collect plot data, employing diverse databases and protocols. Bringing these data together in a consistent and well documented format was and continues to be a major challenge of the project. 

“Historically, vegetation classifications were built by field scientists with a lot of experience. The problem is that it was too subjective. Another scientist could not look at the classification types and replicate the methods used to derive them. The National Vegetation Classification is based on standardized, rigorous data rather than just subjective opinion. The plot data is publically available so that anyone can go back and see it, and the classification can be revised and improved moving forward,” said Robert Peet, a professor at the University of North Carolina at Chapel Hill. Peet was among the instigators of the new classification and has served on ESA’s Panel on Vegetation Classification since its inception, in 1995. 

The classification adopts traditional, widely shared concepts, with terminology that often dates to the early 1900s, but unites these concepts into an effective, coherent system. 

“The USNVC is the first dynamic standard that will evolve as information and data about vegetation in the U.S. is refined—and as global change occurs. We know that vegetation will respond to changes in the environment resulting in novel ecosystems,” said Alexa McKerrow, implementation manager for the U.S. National Vegetation Classification and a biologist for the U.S. Geological Survey. “That doesn’t mean the descriptions of the historical types will go away. We don’t rewrite the sage brush type just because pristine sage brush scrubland is invaded by cheatgrass. We will add new types based on the latest information.” 

NatureServe has worked with the U.S. Forest Service and the U.S. Geological Survey, along with the National Park Service, Bureau of Land Management, and others to ensure the scientific rigor of the classification and facilitate the classification’s development. These agencies continue to fund ongoing peer-reviewed revisions. Jason Harrison, vegetation ecologist at the Maryland Natural Heritage Program believes this collaboration has led to significant advancements in the U.S. National Vegetation Classification over the years.

"In particular," Harrison said, "refinements at the association level have been useful for tracking and assessing the conservation status of state-level vegetation data." 

Throughout the long development of the USNVC, NatureServe’s ecology staff have worked closely with Network programs and now,  using Biotics, are already distributing the classification to program databases, so they can access it for state-level work.  In Virginia, for example, ecologists have been working with other Network programs since 1989 to build the foundation of the USNVC in the Mid-Atlantic region.

"We've collected and analyzed quantitative data from over 4,700 vegetation plots throughout the state," said Karen Patterson, vegetation ecologist with the Virginia Natural Heritage Program. "The USNVC is the structure we use to fit our community classification and conservation efforts into a global context. The Virginia Natural Heritage program tracks 319 USNVC associations in the state of Virginia.  These associations are the conservation targets we use to guide our natural community inventory, protection, and stewardship efforts." 

The ESA Panel on Vegetation Classification will manage the peer review process for revisions and additions to the classification. Established by the Ecological Society in 1995, the panel developed the standards for plot-based survey methods and the peer review system for revising the classification. The panel represents the expertise of professional ecologists spanning academic, agency, and non-governmental sectors and acts as a forum for debate on scientific issues relating to vegetation science and taxonomy. It maintains VegBank, a public data archive for storing, sharing, and displaying information on vegetation types, including the multiple kinds of vegetation plots now being employed in the classification enterprise. Nearly 100,000 plots have already been archived—a good start, say panel members, but only a fraction of what is needed to represent the diversity of vegetation in the U.S. 

“Proposals for classification updates are submitted to a peer review process, much like articles are peer-reviewed for publication in a journal, but because we’re maintaining a system, we have to consider how individual changes or additions will affect the whole. If someone wants to change Mangrove types, we have to be sure that it doesn’t conflict with tropical forest swamp types,” said Faber-Langendoen. 

The panel expects that the lower levels will generate most input and review. The fine-grained, lower levels have also received the least scrutiny and review so far. Levels 5-8 will only change, at most, every five years. 

“People need assurance that it’s stable enough to work with and doesn’t go out of date before you can use it. Thankfully, we’re now at that point,” said Faber-Langendoen. 

The National Park Service has taken the lead in putting the National Vegetation Classification into action for its inventory and monitoring program. The Park Service has inventoried 159 parks, preserves, and other lands under its administration using the classification, and has 88 projects in progress. The Landscape Fire and Resource Management Planning Tools (LANDFIRE) program of the U.S. Department of Agriculture Forest Service and U.S. Department of the Interior is working to cross-walk their classifications based on NatureServe’s Ecological Systems to the group and macrogroup levels of the National Vegetation Classification, which will allow USNVC vegetation plot data to contribute to LANDFIRE’s nationwide mapping efforts. 

Faber-Langendoen and his colleagues hope the launch of the classification will bring it to the attention of a broader section of potential users and draw input from academics, consultants, and other as yet untapped environmental professionals. 

The U.S. National Vegetation Classification (USNVC) Partnership includes: NatureServe, U.S. Forest Service, USGS Core Science Systems, Ecological Society of America (ESA), and the Vegetation Subcommittee of the Federal Geographic Data Committee (FGDC). 

Read more about the details of the classification.