Satellite study tracks three decades of forest growth in southern Spain

Researchers from the Terrestrial Ecology group at the University of Cordoba have harnessed nearly three decades of this satellite imagery (1994-2021) to investigate how forest ecosystems in Andalusia, Spain, have responded to rising aridity. Using the Landsat data, which captures electromagnetic spectrum bands beyond human vision, scientists analyzed seasonal and growth patterns in key Mediterranean forest species. Their focus included holm oak, cork oak, various pine species, eucalyptus, olive, and chestnut trees.

The analysis revealed that Andalusia's forests are now greener than they were 30 years ago, with an overall increase in forest cover. This growth was especially significant between 1994 and 2005. Rafael Villar, who led the study, attributed this change to multiple interacting factors such as rural depopulation leading to land abandonment, natural species adaptation to drier conditions (notably Pinus halepensis and Quercus ilex), atmospheric CO2 enrichment, forest management strategies, and conservation policy shifts.

However, the greening trend is not uniform across the region. Cristina Acosta, a contributing researcher, noted, "this trend towards greening is the result of an average of all of Andalusia over time." Drier zones, particularly in Almeria, saw less dramatic increases in vegetation, with species like Pinus sylvestris showing limited growth due to lower rainfall levels.

The study also documented how arid conditions have affected the growing season of several tree species. Trees such as olive and eucalyptus have experienced shorter growing periods. Wild pine, especially sensitive to reduced precipitation, has adapted by shortening its growth cycle, timing its development based on the onset of autumn rains and the early arrival of summer heat.

According to Pablo Salazar of the Department of Botany, Ecology and Plant Physiology, the research highlights remote sensing as a powerful and efficient approach for monitoring ecosystems under climate stress. He emphasized that satellite-based observation enables ongoing forest assessments, early detection of decline, carbon sink evaluation, and insights into climate change's influence on vegetation. Salazar explained that this approach complements fieldwork while offering broader coverage and faster data acquisition.

Research Report:Aridity-induced phenological shifts and greening trends in Mediterranean forest species: Insights from 28 years of Landsat data in southern Spain