Satellite imagery and climate variables suggest variations in the phenology of olive groves in Southern Spain

Olive groves have high socioeconomic impacts in Spain. Global warming is leading to changes in agrarian systems, affecting phenology and productivity. Remote Sensing data is useful to study the current trends in olive groves. The MEDGOLD project, funded by the European Union's H2020 programme (No. 776467), aims to develop climate services for the Mediterranean agri-food sector (grape, olives and durum wheat). In this work, images from the MODIS sensor have been used to study the status of olive groves in 2000-2020 in Southern Spain. Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI) and Normalized Multi-band Drought Index (NMDI) were computed and correlated with precipitation and temperature using datasets provided by the Environmental Information Network of Andalusia (REDIAM) and scenarios based on the MED-GOLD outcomes. Additionally, some annual indicators were derived from NDVI to study trends: maximum (MAX), minimum (MIN), mean (MEAN), relative range (RREL), date of the maximum (DMAX) and date of the minimum (DMIN). Reported good and bad production years were reflected on vegetation indices. Trends were observed in annual indicators. The average photosynthetic activity increased, especially in MIN (Δyear = 0.0025; r2 = 0.68). The trend of RREL (Δyear = -0.012; r2 = 0.52) indicated that vegetation is moving to a more constant seasonal behaviour. The beginning and end of the season tend to occur earlier each year, as showed by DMAX (Δyear = -2.7 days) and DMIN (Δyear = -1.7 years). Management practices may require adaptations to the new seasonal behaviour of herbaceous vegetation, which could affect soil properties.

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