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The USGS Earth Resources Observation and Science (EROS) Center has released a new online tool to help the public better visualize county-by-county land change across the United States.
The National Land Cover Database (NLCD) Enhanced Visualization and Analysis (EVA) tool lets users pick any county in the U.S. and see how much change has occurred between 2001-2016.
The interactive mapping tool breaks down change with graphs, charts and spreadsheets, and includes special sections showing growth or loss of impervious urban surfaces, forested lands and wetlands. A cropland change viewer is in development.
The release comes in advance of NLCD 2019, which will update the project’s land cover data to reflect 2019 conditions and include additional data on wind energy production, historical information on impervious surfaces, and more.
The EVA tool, developed in partnership with NOAA's Office for Coastal Management, is a user-friendly alternative to bulky data downloads or multi-layered online maps. Jon Dewitz, the NLCD coordinator at EROS, foresees EVA being valuable to students and teachers, new users, and the general public.
“It’s one more way for people to access our land cover information,” Dewitz said. “Land cover has moved from a niche product to one being used every day in people’s lives.”
People began to see a version of land cover each time they put a destination into their phone’s mapping application, Dewitz noted, but smartphone apps don't offer much information about changes through time. The EVA tool helps users without previous GIS training find answers about change and explore an area's history in greater detail.
“This starts to fill that need for new users who want to ask questions and learn more,” Dewitz said. “It also helps land managers and planners quickly get answers to the questions that NLCD was built to answer.”
All of the statistics presented by the EVA tool come from NLCD’s suite of satellite-derived mapping products, which sort each 30-by-30-meter plot of ground in the country into a thematic land cover class, such as cultivated crops, deciduous forest, developed and the like.
NLCD also offers data layers showing developed impervious surfaces (think roads, parking lots and buildings in urban areas) and forest canopy cover for the U.S., as well as layers breaking down rangelands of the Western U.S. into their component parts (sagebrush, shrub, herbaceous and litter, for example).
NLCD data is already available to download at no cost to the user through the Multi-Resolution Land Characteristics (MRLC) consortium website. There are also interactive mapping tools that allow users to zoom in on an area of interest and look at each data later from 2001-2016.
What makes EVA unique is the amount of work that's already done for users. Visitors can limn the outlines of meaningful local stories of landscape change through the county-level stats, which might signal shifts in local industry, climate change impacts, the ripple effects of urban development, agricultural practices, wildfires, invasive species and more.
Since 2001, cropland conversion has been the major driver of change across Potter County, SD's 900 square miles. The EVA tool captures that trend, as well as more nuanced change. The county saw an additional 42.61 square miles of cropland appear from 2001-2016, with a loss of 41.8 square miles of grassland. Open water declined by 7.93 square miles, while emergent herbaceous wetlands grew by 7.15.
Ramsey County, N.D. also saw gains in cropland (23.41 square miles) and losses in grassland (10.8 square miles) from 2001 to 2016, as well as losses in pasture (29.83 square miles). The starkest change, however, came in the form of expansion to the county's most prominent water body: Devil’s Lake. Ramsey County saw an additional 28.29 square miles of open water emerge from 2001-2016, with many of those miles overtaking wetlands.
A different sort of grassland displacement played out in Denton County, TX, a county on northern edge of the Dallas-Fort Worth metro area that's home to the growing exurban enclaves of Denton and Frisco. Denton County added 64.28 square miles of developed land within its borders from 2001-2016, with grassland losses of 63.71 square miles. Nearly one-quarter of the county’s land was developed by 2016, compared to just over 17 percent in 2001.
Denton County also saw an additional 7.36 square miles of cropland, and losses to tree cover of 8.65 square miles.
In Owyhee County, Idaho, the tale is not one of urban growth or cropland expansion, but of fire and invasive grasses. The sparsely-populated western county's 7,697 square miles saw sagebrush areas ravaged by fire several times during the 15 years covered by NLCD mapping products, and the EVA tool’s statistics reflect as much.
More than 656 square miles of grassland were added by 2016—much of it fast-growing, fire-fueling invasive varieties like cheatgrass or Medusa head—while shrubland declined by nearly 671 square miles.
Interested in seeing the story of your own county? Follow this link to access the EVA tool. You’ll be able to see the stats, generate custom reports and download data.
Look for new land cover products to appear with release NLCD 2019, currently scheduled to release in the coming months.
Eyes on Earth is a podcast on remote sensing, Earth observation, land change and science, brought to you by the USGS Earth Resources Observation and Science (EROS) Center. In this episode, we hear how Landsat helps monitor vulnerable rangelands in the Western U.S.
Eyes on Earth is a podcast on remote sensing, Earth observation, land change and science, brought to you by the USGS Earth Resources Observation and Science (EROS) Center. In this episode, we talk about the National Land Cover Database.
The National Land Cover Database (NLCD) provides nation-wide data on land cover and land cover change at the Landsat Thematic Mapper (TM) 30-meter resolution. NLCD provides spatial reference and descriptive data for characteristics of the land surface such as thematic class (e.g., urban, agriculture, and forest), percent impervious surface, and percent tree canopy cover.
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