New National Wetlands Inventory Product Line Supports Strategic Decision Making

The U.S. Fish and Wildlife Service National Wetlands Inventory (NWI) Program provides users with information on wetland and deepwater habitat location, extent, type and change to promote the understanding and conservation of America’s wetlands. The NWI Geospatial Dataset, commonly known as NWI maps, supports a wide array of applications, including climate change climate change
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resilience, infrastructure planning, habitat and species conservation, energy production and clean drinking water provision. The American public frequently relies on the dataset, as illustrated by nearly a million website views and 40,000 dataset downloads annually, but resources have not been available to regularly update the entire dataset.

To address this challenge the NWI Program is working with partners to leverage the best of different datasets and techniques, thus enhancing dataset utility and production efficiency. One example of this is NWI’s newly developed Difference Product Line, which provides information on where land cover change is most likely to have occurred since NWI data production. This product line: 1) supports effective investment in the Geospatial Dataset by allowing stakeholders to strategically target geographies in greatest need of updates; 2) empowers dataset users to make critical decisions regarding dataset suitability; and 3) enables more effective coordination with the NWI Program.

Wetland to Impervious Surface Difference Product for census tracts in the Contiguous US. Census tracts with ≤0.05% of wetland to impervious surface difference, calculated by area, are displayed in gray, while those that have greater than half a percent difference are displayed in dark red. Patterns are largely controlled by the age of National Wetlands Inventory (NWI) data and development trends. Thus areas that exhibit greater difference (i.e., change) may have older NWI data, more development, or both. These areas are commonly found near cities. Note that although there are concentrated areas of difference, likely change due to impervious increase, the vast majority of the United States has not experienced this level of change since NWI data production and therefore has NWI data that better represent current land cover. Geographies with the greatest levels of difference could be prioritized for NWI updates
Upland to Open Water Difference Product for HUC12 watersheds in the contiguous U.S. Watersheds with ≤0.5% of upland to open water difference, calculated by area, are displayed in gray, while those that have greater than 2% difference are displayed in dark blue. Patterns are largely controlled by the age of National Wetlands Inventory (NWI) data and land cover trends, including the addition or increase in pond and lake area via natural and anthropogenic forces. Areas exhibiting the greatest amount of difference (i.e., change) include the Prairie Pothole Region and the southeastern U.S. Geographies with the greatest levels of difference could be prioritized for NWI updates.
Vegetated Wetland to Open Water Difference Product for HUC12 watersheds in the contiguous U.S. Watersheds with ≤0.5% of vegetated wetland to open water difference, calculated by area, are displayed in gray, while those that have greater than 2% of difference are displayed in dark blue. Patterns are largely controlled by the age of National Wetlands Inventory (NWI) data and land cover trends, including the conversion of drier-end vegetated wetlands to open water via natural and anthropogenic forces. Areas exhibiting the greatest amount of difference (i.e., change) include the Prairie Pothole Region and the Mississippi River Floodplain and Delta. Geographies with the greatest levels of difference could be prioritized for NWI updates.

Difference Products were created, in partnership with the University of Maryland, by comparing the NWI Geospatial Dataset with other federal land cover products to identify areas where wetland or deepwater habitats are likely to have been gained or lost since Geospatial Dataset production. More specifically, areas are identified where the following changes are likely: 1) wetland or deepwater habitat lost to impervious surface; 2) vegetated wetland changed to open water; and 3) open water gained on upland.

Raster Difference Product for an area near Houston, Texas. Mapped classes highlight areas that have likely experienced land cover change since National Wetlands Inventory Geospatial Dataset production, including loss of wetlands or deepwater to impervious surface (red), gain of open water on upland (dark blue), and gain of open water on drier-end vegetated wetland (light blue).

In celebration of American Wetlands Month NWI is providing early access to this information for watersheds or census tracts throughout the contiguous U.S. Since these data highlight differences, mostly land cover change, relative to dataset production date the products should not be used to indicate wetland loss/gain trends at the national scale. Instead, they can be used to identify geographies that could be prioritized for NWI Geospatial Dataset updates, or to inform data use decisions. The products and related information can be accessed below.

Upland to Open Water Difference Product – HUC12 Watersheds

Vegetated Wetland to Open Water Difference Product – HUC12 Watersheds

Wetland to Impervious Surface Difference Product – Census Tracts

Stay tuned for more news on this product line, as well as more detailed products!

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Wetlands