How Landsat Helps New Hampshire

New Hampshire measures just 80 miles across at its widest and 175 miles from north to south, yet few states pack in as much rugged natural beauty per mile as the nation's fifth smallest. Its 93 state parks are home to moose, black bears, coyotes, beavers, river otters and foxes. The largest section of White Mountain National Forest crosses the north-central part of the state, drawing visitors to its lakes, streams, peaks and hardwood forests. Lake Winnipesaukee, the largest lake, is known for its floating post offices, a yearly contest to guess the date its ice goes out, and roles in films such as On Golden Pond and What About Bob?

The state's forests face invasive pests — the spongy moth, balsam woolly adelgid and emerald ash borer — and its lakes and streams have seen more cyanobacterial blooms in recent years. The U.S. Geological Survey's Landsat program, a consistent, reliable and unmatched record of Earth observations, helps map, monitor and manage the state's land and water.

Water quality

Too many nutrients in a lake cause bad smells, unsightly algae and, most seriously, cyanobacterial blooms that can endanger human health. New Hampshire has long relied on volunteers to collect water samples, but Landsat offers a low-cost supplement: its sensitive sensors, which see beyond visible light, can detect chlorophyll a, a measure of algal growth. A 2018 study found that Landsat 8 measurements of chlorophyll a closely matched on-the-ground measurements in several New Hampshire lakes, a quicker, less labor-intensive option.

In June 2016 USGS scientists deployed a high-tech buoy that helps determine when the water at Weirs Beach on Lake Winnipesaukee is safe for swimming; Landsat can help by spotting harmful algal blooms over wide areas. Photo by Richard Kiah, USGS.

Forests

Nearly 80% of New Hampshire is forested, second only to Maine, so forest health is a good gauge of the state's landscape as a whole. With repeated observations and 30-meter resolution — each pixel is about the size of a baseball infield — Landsat is well suited to studying forest change. Researchers have used it to track conifers slowly spreading into lower elevations of the White Mountains and to measure the forests' net primary productivity, the carbon trees absorb minus what they lose through respiration.

Landsat's near-infrared and shortwave infrared bands reveal forest damage such as this 2021 defoliation, in a summer when the invasive spongy moth reemerged as a threat. USGS image.

Land use and land cover

Landsat underpins national land cover mapping such as the National Land Cover Database and the National Oceanic and Atmospheric Administration's Coastal Change Analysis Program, which state and local officials can use to model changes to cities, wetlands, coasts, forests and grasslands. In 2017, geographers at the University of New Hampshire's Earth Systems Research Center modeled six scenarios for how the state's landscape might change from 2010 to 2100, guiding decisions on development and environmental policy.

Landsat nationwide

The USGS National Land Imaging Program makes Landsat data available worldwide, free of charge, through the USGS Earth Resources Observation and Science (EROS) Center. Landsat is the most widely used land remote sensing source in federal civilian agencies, and local, state and tribal agencies rely on it too, for decisions that protect life and property, safeguard the environment, advance science and education, and support the economy. Businesses use it to improve logistics and investment decisions, and a 2024 study put its total annual economic benefit at $25.6 billion, far more than its cost. Landsat 8 and 9 together image Earth's land every 8 days, and NASA and the USGS are working toward a 2031 launch of Landsat 10 to continue the more than 50-year record, the longest of Earth's land surface.

Sources

• U.S. Geological Survey: "New Hampshire and Landsat," a fact sheet citing Boucher and others (2018), Vogelmann and others (2012), Potter and others (2007), Thorn and others (2017) and Loomis and others (2024).