Plastic-covered greenhouses mapping in Morocco with Google Earth engine: Comparing Sentinel-2 and Landsat-8 data using pixel- and object-based methods

Abstract

With the ever-increasing demand for food production, monitoring plastic-covered greenhouse (PCG) spatiotemporal distribution accurately holds significant importance for monitoring agricultural expansion and environmental impacts. For this purpose, in this paper, we used a random forest (RF) algorithm to produce multi-temporal PCGs maps in three different intensive agricultural Moroccan areas (Loukkos (LS), Gharb (GB), and Souss-Mass (SM)). Two classification approaches, object-based (OB) and pixel-based (PB), were applied to Landsat-8 (L8) and Sentinel-2 (S2) imagery via the Google Earth Engine (GEE) platform. Additionally, the RF performance is compared across five feature scenarios, combining spectral bands, spectral indices, and texture information. Further, we estimated the PCGs' spatiotemporal dynamics from 2018 to 2023. Findings indicated that the Blue and SWIR bands, Normalized Difference Tillage Index (NDTI), Plastic-Mulched Landcover Index (PMLI), variance, and sum average texture were the most significant variables that contributed to accuracy in PCGs classification. The 6-year average overall accuracy achieved >93.10% in mapping PCGs. Notably, the band combination “All” (Bands + Indices + Texture) produced high overall accuracy (>94.9%) and F1-score (>91.8%) compared to other feature combinations. Nevertheless, we found considerably improved classification accuracy by combining only spectral indices with texture (OA >94.6%). It was noticed that both OB and PB approaches reveal their similar performance in most cases, with slight differences. Besides, the PCGs estimated area analysis showed that SM area had the largest PCG coverage, approximately three times larger than the other areas, and it exhibited an overall growth of +8.45% between 2018 and 2023. Thus, this research demonstrates the RF and OB-PB's capability to accurately identify PCGs in GEE. In addition, these results can serve as valuable insights for policymakers and agricultural planners to efficiently monitor and manage PCGs expansion in intensive agricultural areas.