Using Google Earth Engine for the analysis of fog and forest landscape interactions in hyper-arid areas of southern Peru

Hyper-arid dryland ecosystems are particularly vulnerable to climate change and human influences, due to their dependence on advection fog as main water source. In these so-called ‘fogscapes’, human-induced fog collection represents a sustainable technology for fostering reforestation and, thus, increasing soil fertility and combating desertification. Along Atacama Desert coastal line, the effect of the Humboldt Current generates large scale fog events on the coastal belt, lasting from June to December, and the vegetation of the first hilly ridges (locally “lomas ecosystems”) may favour of the water content of fog. The University of Florence has set up a long-term research on fog collection associated to reforestation actions in two experimental plots in South Peru at the site of the Lomas de Mejia. 20 Large Fog Collectors were installed in 1996 to collect water from fog, for irrigating the trees and shrubs planted in the experimental plots. The irrigation lasted two years, then the established trees and shrubs were left to collect fog by themselves. The paper presents the results of a long-term remote sensing monitoring of the area, based on the use of Google Earth Engine platform. More than 20 years of NDVI time series for the two reforested parcels and portions of an external control area, were generated and analysed. NDVI time series analysis shows the evolution of the parcels from bare soil to vegetated portions and its development in time. Results show the important role of advection fog for inducing the re-vegetation of areas where forest was previously present, the significant increments of vegetation cover for the reforested parcels in time, encouraging the implementation of fog collection projects for land rehabilitation in areas with similar characteristics.