Landsat Helps Bolster Food Security: Satellites in the Famine Early Warning System

In sub-Saharan Africa, where famine can be the only yield of a scorched land, survival may hinge on how far away the feeding centre is and how close the nearest well. Satellite imagery has become a valuable tool for the officials who must respond. In 1966 Interior Secretary Stewart Udall proposed turning satellites on Earth's natural resources — "a vision to observe Earth for the benefit of all." That idea became central to the Famine Early Warning Systems Network (FEWS NET), started in 1985 by the U.S. Agency for International Development (USAID), which relies heavily on the U.S. Geological Survey and other federal agencies for timely, accurate data to help countries detect agricultural drought early and head off famine.

Landsat's growing role

Coarse images from weather satellites have been part of FEWS NET almost from the start. Landsat's role has grown in recent years, says Michael Budde, a USGS geographer at the Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota. Large-scale processing by Google Earth Engine and others now makes huge global datasets easy to analyse — made possible by the USGS decision in 2008 to release Landsat data free — opening the door to products useful for FEWS NET in Africa, Central America and Central Asia.

Water

Combining Landsat data with rainfall and runoff data, USGS scientists have built models that accurately predict how much water is available and used in a region. They work well in the western United States, where researchers map evapotranspiration (ET) — water given off by plants and evaporated from the ground. Landsat-based ET measures are useful worldwide, at local scale, to spot water shortages for crops and the resulting drop in food production.

Evapotranspiration in an irrigation district of South Africa, October 2013–February 2014: blue and green mark greater water use, yellow and orange less; the blue circles are center-pivot irrigation, where use is highest. USGS.

Crops

Satellite sensors measure the wavelengths of light that green plants absorb and reflect, and the data become vegetation indices that describe how dense and healthy vegetation is. With Landsat's 30-metre resolution, these assessments are nearly 70 times more detailed than those from moderate-resolution satellites.

Because the European Space Agency's Sentinel-2 is compatible with Landsat 7 and 8, the same places are imaged more often. That helps study crop management where fields are big enough, and to check coarser products on snowmelt, flooding and the mapping of irrigation.

For decision makers

Landsat gives decision makers crucial information on crops, natural vegetation and water. It helps agencies decide where to send food aid by showing where flooding or drought has left one area worse off than another, and USAID officials say FEWS NET's evidence matters in their decisions. As remote sensing improves, Landsat and FEWS NET will keep providing answers for people whose survival depends on them.

Sources

• U.S. Geological Survey, Landsat Helps Bolster Food Security, Fact Sheet 2016–3060, version 1.1, September 2019. https://doi.org/10.3133/fs20163060
• USGS Earth Resources Observation and Science Center: https://www.usgs.gov/centers/eros
• A photograph on the sheet's cover, without a credit, is not reproduced here.