Happy 40th Birthday to IMPROVE Program, research protecting visibility across the United States
By Theresa Barosh | April 2025
This year, a program called Interagency Monitoring of Protected Visual Environments, also known as IMPROVE, celebrates 40 years of monitoring to protect visibility in the country’s most pristine locations.
The IMPROVE program monitors air quality in national parks and wilderness areas. Data from the program are used to track progress under EPA’s Regional Haze Rule towards clear air. Countless scientific studies on air quality in the United States use data from the program, which is considered a “gold standard” for long-term monitoring programs due to the rigorous efforts of teams of researchers. Dramatic improvements in air quality across the U.S. have been demonstrated using IMPROVE data.
The program originated at Colorado State University’s Cooperative Institute for Research in the Atmosphere, a partnership between the University and NOAA. IMPROVE is a collaborative monitoring effort between the National Park Service, EPA and other key partners.
CIRA researcher Jenny Hand, lead scientist on the project, shared three facts about the research.
1. Haze can affect scenic vistas.
Unfortunately, views are sometimes obscured by haze, which consists of fine particles in the atmosphere. Although haze does occur naturally, due to things such as dust and wildfire smoke, it is primarily caused by air pollution resulting from human activity.
2. Visibility in national parks has improved dramatically over the past decades.
Due to successful regulatory activity that has reduced emissions of air pollution, the nation’s most scenic places have experienced significant improvements in visibility. Vistas which were once obscured by haze are returning to more natural conditions for visitors to experience. Tracking these changes in air quality would not be possible without the IMPROVE program.
3. IMPROVE researchers monitor air quality at over 150 sites.
IMPROVE monitors collect 24-hour samples of particles every three days at national parks and other remote sites. Researchers can use this information to determine how much haze is present as well as deduce the sources of the haze. Some sites also include a webcam for documenting scenic views.
Historical Context
Recognizing the importance of visual air quality, congress included legislation in the 1977 Clean Air Act to prevent future and remedy existing visibility impairment at national parks and other federally protected areas. To aid in the implementation of this legislation, the IMPROVE program was initiated in 1985 to provide monitoring of visibility in these locations. Researchers say they are proud of the uniquely long data record from the program, approaching four decades, and they look forward to continuing the important work of protecting visibility in these special places.
What is needed: Continued funding to maintain air quality monitoring to protect national park views.
