Have you ever questioned if there would be enough food at the store for everyone in your community? If you frequent a grocery store or market, probably not. Every Sunday I go to the grocery store with a list of foods I’ll need for the week and no contingency plan for what to do if there isn’t enough. If something is out of stock, I’ll just go to the next grocery store down the road. We take it for granted that certain foods will always be available for us to purchase. However, many people do not have the luxury of a reliable food source. In 2020, 34.8% of the people in Latin America, 55.5% of the people in Africa, 23.6% of people in Asia, 12.9% of people in Oceania, and 8% of people in North America and Europe experienced moderate or severe food insecurity (FAO, 2020). In Latin America, Africa, and Asia, these numbers are up from previous years—in 2015, only 27.9%, 48.8% and 19% of the population experienced food insecurity, respectively (FAO, 2020). As the global population continues to boom and climate change continues to challenge food and water systems, more people may no longer be able to take food security for granted. However, we now have a new space-based technology combatting food insecurity.

In the age of anthropogenic climate change, ensuring agriculture productivity and sustainable food production has become a challenge for agricultural systems. Consequently, protecting food security is a developing problem. The United Nations Food and Agriculture Organization (FAO) says that:
“food security exists when all people, at all times, have physical and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life” -FAO at the World Food Summit (1996).
Until 2015, the world was making progress toward improving food security and accomplishing the second Sustainable Development Goal (SDG), which seeks to end world hunger. However, if the recent trend in increasing rates of food insecurity continues, 840 million people will experience chronic hunger by 2030 (WFP, 2020) (Figure 1). Among other things, climate change is a major driver of food insecurity because of its effect on crop yields. For example, between 1964 and 2007, droughts and extreme heat decreased global cereal yields by 10% (Lesk, 2016). In their 2020 report on the state of food security in the world, FAO and their collaborators identified climate variability and extremes as one of the major drivers of food insecurity (Figure 2).

A stressful environment, including very warm temperatures or dry conditions, affects how plants work. Warmer temperatures and/or a lack of available water requires plants slow or stop their growth processes to preserve water in order to survive, which decreases plant productivity. Losses in plant productivity result in reduced crop yields (Farooq, 2009). Evapotranspiration (ET) can be a useful indicator of stressful conditions. Because it links water to plants, ET can provide information about water stress and how the terrestrial biosphere is responding to climate change (Fischer, 2017). Thus, monitoring ET changes provides valuable information for more effective crop and water management.
Monitoring crops from space
A recently launched satellite is a promising new technology for monitoring crop conditions and protecting food security from space. The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission seeks to understand if agricultural vulnerability can be reduced through advanced monitoring of agricultural water consumptive use and improved drought estimation. Using a thermal radiometer docked on the International Space Station (ISS), ECOSTRESS measures thermal energy (a.k.a. heat) coming from the Earth, which is then used to calculate ET, water stress, and water use efficiency maps. With a revisit time of every 3-5 days, we can now see how crops are doing at the sub-weekly scale.
ECOSTRESS provides a unique dataset because of its orbital path and technology. It gives global coverage at the scale of a farmer’s field (~70 m resolution) and because it is on the ISS, it provides data at different hours of the day on each overpass. Many other satellites are in sun-synchronous orbit, meaning they always go over the same geographic location on earth at about the same time of day. With ECOSTRESS, we can now see how plants are responding to different conditions at different times of the day and year
Humans can help crops adapt to changes in environmental conditions if they have the right information. With the temporal frequency and spatial scale of ECOSTRESS, it is timely enough and at the right scale (i.e., it gives information at a small enough scale) that farmers can utilize the data to inform irrigation decisions. See Figure 3 for the level of detail an ECOSTRESS image provides. When plants “transpire” (the T part of ET), it cools them. While also a function of water availability, warmer plant temperatures generally mean that the plants are experiencing more stress. Therefore, by measuring heat, ECOSTRESS provides a dataset for better understanding how much water plants need and when. Many of the other satellites in orbit only provide information about plant stress when plants are visibly brown. By that time, it is too late to do anything. With ECOSTRESS, farmers can now see the slow onset of drought or water stress experienced by the crops and either prepare for decreases in yield or proactively mitigate against losses by irrigating more. ECOSTRESS is a tool that can help maintain crop productivity and yields without needlessly wasting water.
While only launched in June 2018, farmers have already begun to integrate ECOSTRESS into their decision making about precision irrigation. By utilizing ECOSTRESS data in apps designed to help farmers irrigate their fields with only the necessary amount of water, some companies are seeking to maximize water use and crop yields (NASA JPL, n.d).
A European Space Agency sponsored group—Food Security TEP—also utilizes ECOSTRESS for protecting food security. They seek to help small-scale farmers and international bodies alike become more resilient to unstable climate conditions and ultimately, support efficient and sustainable farming.
Although climate change will continue to challenge the global agricultural system throughout the 21st century, space technologies such as ECOSTRESS are making it easier for humans to protect food security and continue toward accomplishing the second SDG. Despite being thousands of miles away, ECOSTRESS is connecting farmers to their fields in new and unique ways, helping to ensure that our favorite foods are always in the grocery store and people around the world have enough to eat.

Note: This work was done as a private venture and not in the author's capacity as an employee of the Jet Propulsion Laboratory, California Institute of Technology.
FAO, IFAD, UNICEF, WFP and WHO. “The State of Food Security and Nutrition in the World 2021. Transforming food systems for food security, improved nutrition and affordable healthy diets for all.” Rome, FAO (2021). https://doi.org/10.4060/cb4474en.
Farooq, M., A. Wahid, N. Kobayashi, D. Fujita, and S.M.A. Basra. “Plant drought stress: effects, mechanisms, and management.” Agronomy for Sustainable Development 29, (March 2009): 185-212. https://doi.org/10.1051/agro:2008021
Fischer, Joshua B., Forrest Melton, Elizabeth Middleton, Christopher Hain, Martha Anderson, Richard Allen, Matthew McCabe, et al. “The future of evapotranspiration: Global requirements for ecosystem functioning, carbon and climate feedbacks, agricultural management, and water resources.” Water Resources Research 53, (March 2017): 2618-2626. https://doi.org/10.1002/2016WR020175.
NASA JPL. “ECOSTRESS Gallery.” https://ecostress.jpl.nasa.gov/gallery/viewgalleryimage
NASA JPL. “ECOSTRESS Pivotal in Precision Agriculture.” (n.d.) https://ecostress.jpl.nasa.gov/news/ecostress-pivotal-in-precision-agri…
NASA JPL. “ECOSTRESS.” (n.d.) https://ecostress.jpl.nasa.gov/
Lesk, Corey, Pedram Rowhani, and Navin Ramankutty. “Influence of extreme weather disasters on global crop production.” Nature 529, (January 2016): 84-87. https://doi.org/10.1038/nature16467.
World Food Program (WFP). “Hunger Map”. (August 2020). https://www.wfp.org/publications/hunger-map-2020
World Food Summit 1996, Rome Declaration on World Food Security.