 The rain use efficiency, RUE, is a measure of how much biomass is produced per unit of rainwater. It is often used to compare the productivity of different ecosystems and determine whether they are being affected by drought or other environmental factors. However, when using satellite imagery to calculate RUE, it is important to consider the effects of precipitation on the amount of biomass produced. If the satellite imagery does not account for the effect of precipitation, then the RUE value will be misleading and unreliable. This study found that when using satellite imagery to calculate RUE, it is important to take into consideration the effect of precipitation on the amount of biomass produced. When doing so, the RUE values were more accurate and reliable. This article was authored by Els Swinnin, Stephanie Horian, Per Casperson, and others.