LCMAP: How the USGS Tracks Land Change Across the United States

LCMAP turns each location's Landsat record — from Landsat 4 through Landsat 8 — into 5 spectral change products and 5 land cover products. USGS.

Why it exists

Land around the world is changing fast, and it needs to be monitored and understood. The U.S. Geological Survey's Land Change Monitoring, Assessment, and Projection (LCMAP) capability — the Earth Resources Observation and Science (EROS) Center's foundation for USGS-wide land change science — produces consistent data and land cover products over large areas, long periods and at higher frequency than before (Brown and others, 2020). It helps scientists and managers understand what drives land change, its consequences for people and nature, and its feedbacks.

What LCMAP provides:

• continuous tracking of land change;
• tools to monitor land cover and vegetation condition;
• assessments of the rates, causes and consequences of change;
• data on past, present and future landscapes;
• support for environmental management and policy;
• open sharing of data, information and tools.

Monitoring: every pixel, every year

Past large-scale efforts mapped a few reference dates. LCMAP's basic unit is the time series of satellite measurements at a single pixel — a 30-meter by 30-meter square — so it can use many more dates and date changes more precisely.

• Input: Landsat Analysis Ready Data (Dwyer and others, 2018).
• Method: the Continuous Change Detection and Classification algorithm detects spectral change in each pixel's history, and the model information feeds land cover classification.
• Coverage: results apply continuously from the mid-1980s to now, released as annual products, regularly updated. More frequent updates are being researched, and Sentinel-2 data may be added.
• Accuracy: checked against an independent reference set — land cover interpreted for each year from 1984 to 2017 at 25,000 random sites across the country.

One forested pixel in Washington through the Round Mountain fire of late summer 1994: land cover shows grass/shrub regrowth after the fire, and by 2016 parts of the burn had recovered to mature trees. USGS.

Assessment: where, how much, how fast, and why

Frequent land change mapping offers a new view of U.S. land use and land cover (LULC) change, and helps research on many environmental issues. LCMAP's first regional-to-national assessments ask: where did change occur, how much, at what rates, and what caused it?

Land cover change around Charlotte, North Carolina, grouped into multiyear intervals. The unchanged center is black; color shows change since 1986 — urban growth along the Interstate 485 beltway, a reservoir built in the early 1990s to the north, and patches of change to the southeast. USGS.

Projection

LCMAP land cover can be projected — extended into the future, or back into years before satellite data — to study effects on biodiversity, water, climate and weather. The Forecasting Scenarios (FORE-SCE) model makes 30-meter projections that match LCMAP's land cover, using real land management parcels for realistic landscape patterns.

Example: the tornadoes of April 2011

On April 27, 2011, a record number of tornadoes struck the southern United States, killing people and destroying property. Landsat confirmed their paths around Tuscaloosa and Birmingham, Alabama:

• Before and after: Landsat images from weeks before the outbreak, and from June, show the new tornado paths.
• Annual Land Cover Change: marks the land the tornadoes changed, as of July 1, 2011.
• Time of Spectral Change: estimates the day each change happened — early May 2011, just after the storm.
• Change Magnitude: shows three distinct tornado paths, with moderate surface change here, and other land changes as patches.

The Tuscaloosa–Birmingham area before and after the outbreak, and LCMAP's land cover change product. USGS.

Sources

Based on Land Change Monitoring, Assessment, and Projection, USGS Fact Sheet 2020–3024, U.S. Geological Survey; a work of the United States government in the public domain. The figures and the list of what LCMAP provides are taken from the fact sheet's PDF, which the import had left out.