NWI at 50: the Impact and Future of Wetlands Data

Image: Map displaying the difference between field-surveyed wetland boundaries using Ecobot against the outdated NWI wetland polygon.

If you’re an environmental scientist, you’ve likely used the tools derived from the National Wetlands Inventory (NWI) many times for environmental assessments. But do you know how and when NWI data is collected, and how the program runs?

The National Wetlands Inventory (NWI) and Its Use Cases

Let’s start with some background. NWI is a 50-year-old public geospatial dataset maintained by the U.S. Fish and Wildlife Service (USFWS). It was created in 1974 to record and monitor wetland area, location, type, and trends, to inform land use and conservation decisions at scale. The dataset covers the conterminous United States, Hawaii, Puerto Rico, the Virgin Islands, Guam, the major Northern Mariana Islands and Alaska. Coverage varies by region, with some areas more recently mapped than others.

NWI data is disseminated via two primary outputs:

• Status and Trends Reports These reports are released on a decadal basis to congress per a mandate by the Emergency Wetlands Resources Act (Public Law 99-645). These reports provide a view of long-term wetland evolution across the country to inform conservation and management strategies and policy implementation. Read our summary of the most recent report: Takeaways from the USFWS 2019 Wetlands Status and Trends Report

• Wetlands Mapper This tool provides a map view of wetland and riparian areas across the country. Natural resources professionals can use this tool to prepare for site visits, and provide an idea of what to expect.

  Note: The Wetlands Mapper was designed based on a biological definition of wetlands, and does NOT define regulatory scope or boundaries. Therefore, the map cannot be used for jurisdictional determinations in lieu of an official wetland delineation.

• Status Mapper
  This tool is a corollary to the Wetlands Mapper, and provides a separate view of when mapping efforts were completed or are currently underway.

These tools are widely used by consultants, agency staff, researchers, and NGOs for pre-field planning or scoping.

NWI data supports Clean Water Act permitting, conservation planning, ecological restoration, mitigation banking, infrastructure development, and long-term environmental research. Some recent use cases include:

• Bioenergetics modeling: Ducks Unlimited uses NWI to model food availability for dabbling ducks at the HUC12 watershed level, informing conservation priorities through tools like the American Black Duck Decision Support Tool.
• Climate resilience planning: New Mexico’s Wetland Jewels initiative prioritizes wetland restoration and conservation in areas that mitigate drought, wildfire, and flooding.
• Infrastructure risk reduction: Dewberry applies NWI data in FEMA hazard mitigation projects and storm surge modeling to support early-stage siting and permitting.

NWI Updates—Cadence, Technology, and Challenges

NWI data updates follow a biannual release schedule. USFWS says the data has been updated at a rate covering 50–100 million acres of project area per year. The May 2025 update included over 91 million project acres across 17 states. USFWS says that 2024 was one of the largest ever updates to NWI, and they expect 2025 to match or exceed that standard. 

The NWI dataset is developed using remote sensing techniques and field verification. Trained analysts use aerial imagery to identify and classify wetlands. GIS tools are then used to digitize, classify, and distribute the data. 

During a June 2025 NWI-focused webinar hosted by the National Association of Wetland Managers (NAWM), Megan Lang, Chief Scientist of the NWI program, described ongoing efforts to employ artificial intelligence for wetlands identification and mapping, though the results produced by AI do not yet meet NWI’s spatial and categorical standards. Andy Robertson of St. Mary’s University of Minnesota, said machine learning technology has already enabled 20-30% time savings when producing map layers, while Jes Skillman of Ducks Unlimited described the benefits of deep learning to support data interpretation. As Lang put it: “We have found [AI] to be useful in some respects…but it’s not an easy button just yet.” Those working on NWI remain hopeful that improvements to the technology will increasingly bolster efficient and cost-effective data production in the future.

Some states like Missouri are driving modernization efforts by integrating Elevation-Derived Hydrography (EDH), leaf-off and leaf-on high-resolution imagery, and LiDAR-based topography, said Frank Nelson of the Missouri Department of Conservation. This allows for more precise mapping of wetlands, including small water bodies that were previously missed. In Missouri’s Ozarks, recent mapping reclassified large areas of general “riverine” wetlands into distinct categories (emergent, forested, and shrub) demonstrating the power of better imagery and collaborative data layering.

Lack of Funding Hinders NWI Updates

Technologically, NWI has made enormous strides since its inception. Back then, the maps were drawn by hand, and staff used stereoscopes to identify low-lying land typical of wetland formations. Now, the tools used for NWI include automated approaches that rely on satellite imagery and artificial intelligence, and partnerships with private companies, nonprofits, universities, and other government agencies are driving ever faster innovations.

But even with these advances, much of the country relies on NWI maps derived from imagery that is decades old: as of February 2024, 63% of the NWI map data was over 30 years old, and 88% was over 10 years old. This is especially true in regions where updates have not been possible due to limited funding. Patchy coverage can make it harder to identify recent wetland changes and may complicate early-stage field planning or regulatory coordination, even though NWI data itself does not determine jurisdictionality.

These gaps matter, both for long-term monitoring purposes, and as an effective tool for land use planning in the short term. Better mapping supports better science and policy.

Funding the NWI is an ongoing problem. The budget has been flat since 2016, despite expanding data needs and technology costs. In early 2024, Ecobot joined NAWM, Ducks Unlimited, Environmental Policy Innovation Center (EPIC), St. Mary’s University of Minnesota, and other environmental groups in Washington D.C. to advocate before Congress for funding the NWI. This effort, organized by partners in conservation, was grounded in a shared belief that accurate, accessible data is foundational—not optional—for environmental work.

During NAWM’s recent NWI webinar, panelists discussed the patchwork nature of NWI funding  and updates. Congressional funding has not historically addressed NWI’s needs fully. Instead, state environmental leaders and major NWI data contributors described how ongoing updates are funded in parts by EPA, BLM, DOTs, universities, or other invested parties who benefit from the data, often by way of a “pass of the hat” fundraising effort to track down money as data needs arise. 

Additional funding would allow USFWS to accelerate updates in under-mapped regions, expand QA/QC efforts, and modernize data access platforms. We know that the value of NWI is directly tied to its accuracy, coverage, and frequency of update. From field consultants to regulators to restoration planners, a robust NWI is in everyone’s best interest. As wetland policy, restoration, and climate adaptation efforts grow more urgent, ensuring the NWI remains current and well-supported is essential to meeting those goals.

Ecobot’s mapping tool includes the NWI data layer. This layer is updated with each NWI release.