Peru’s coast is getting greener, but that’s not good news

Over the past twenty years, a large area of Peruvian coastlong About two thousand kilometers, it has changed a lot: once it was dry and desert, now it looks greener. To find out, analyzing two decades of satellite data, a group of scientists from the Cavendish Laboratory was in Cambridge UniversityWho detailed the analysis in an article published in the journal Remote Sensing. Encouraging as the news may seem, in some ways a contrast desertification and onSoil drying which is often talked about, the authors of the work emphasize how this “greening” (greening) is actually a danger to species living in adjacent ecosystems, which will struggle to survive with the limited resources of the area.

he said “our discovery” Hugo Lepage, a mathematician at the University of Cambridge and co-author of the just-published paper, “is a clear warning sign that something is changing, a kind of canary in the mine.” To study this phenomenon, the scientists – a group of mathematicians, geographers and biologists – examined satellite images of the area taken between 2000 and 2020 and developed a mathematical model to make the data independent of meteorological events and seasonality: “It took three years to improve the methodology and the statistical model.” .

“We had to make sure that what we were looking at wasn’t due to statistical fluctuations.” To further corroborate the data, the scientists then observed the conditions in the area live on, on many repeated expeditions over time: “We started from a very small area,” he says. Eustace Barnesone of the authors of the work, “to study the effect of mining activity on the local vegetation, and we realized that the area was turning green and the vegetation was not depleted. By expanding the field, we realized that this phenomenon was also occurring on a larger scale.”

What the researchers saw, in particular, is Having a huge green strip that starts at the bottom of the Peruvian coast, about 200 meters above sea level, and which moving south reaches much higher altitudes of up to 4,000 metres.; Moreover, this range does not “align” with predictions of the so-called Koppen-Geiger classification, which is the system most commonly used to “match” vegetation and climate scale. Lepage continues: “In northern Peru, the stripe is mostly green Its climatic zone should correspond to the arid desert; To the south, then on the border of the steppe climatic zone. Either way, the scenario is very different from what one would expect.”

The authors say the study’s findings have profound implications for the region’s environmental management: although Causes (and consequences) of greening Not yet fully recognized, such a significant change in vegetation “will certainly have an impact on ecosystems and the environment: two-thirds of Peru is supplied by the Pacific slope with water, and most of the food resources also come from that region. This change will inevitably have consequences for Water management and on agricultural planningIt remains to study which ones, to understand how it would be better to act.