Of course, citizens of central Chile are accustomed to long spells of dry weather. However, the past decade has brought an extreme drought that is remarkable even for a region with a semi-arid Mediterranean climate.
Central Chile, where most Chileans live, has received 30 percent less rainfall than normal over the past decade, a situation that scientists are referring to as “mega-drought.” With rainfall deficits of 80 to 90 percent, 2019 has been particularly dry.
Landscapes that would normally be lush and green have withered. The map above depicts the Normalized Difference Vegetation Index (NDVI), a measure of the health and greenness of vegetation based on how much red and near-infrared light it reflects. Healthy vegetation with lots of chlorophyll reflects more near-infrared light and less visible light. The NDVI anomaly map above is based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite between September 5 and November 5, 2019.
The map contrasts vegetation health against the long-term average (2000–2010) for that period. Brown indicates vegetation that is less abundant and healthy than normal for this time of year. MODIS-based land cover data has been used to highlight areas that are snowy, icy, or have minimal vegetation. These areas appear gray. Green areas, mostly in valleys near glaciers and snow cover, have unusually abundant vegetation, likely because of increased melt and runoff from snow and glaciers.
“An 80 percent deficit means that the semi-arid region north of Santiago has seen almost no water, as seen in the marked browning of the vegetation,” said René D. Garreaud, a scientist at the University of Chile. “South of Santiago has received some rain—100 to 300 millimeters (4 to 12 inches). That is still not much, but it has been enough to keep the vegetation green.”