Spatiotemporal dynamics and driving mechanisms of plastic pollutant emissions from agricultural greenhouses in China

Greenhouses are increasingly recognized as hotspots of agricultural plastic pollution, yet the spatiotemporal dynamics of their pollutant emissions and the mechanisms by which natural, management, and socio-economic drivers jointly regulate these emissions remain poorly quantified. Thus, we integrated time-series Landsat imagery on the Google Earth Engine (GEE) platform with a prefecture-city-level emission inventory to quantify emissions of 2 representative phthalate esters (Dibutyl phthalate (DBP) and Bis(2-ethylhexyl) phthalate (DEHP)) from China's agricultural greenhouses during 2005–2024. We then coupled Random Forest (RF) with SHapley Additive exPlanations (SHAP) interpretation to identify dominant drivers and their key thresholds, and applied partial least squares structural equation modeling (PLS-SEM) to decompose the direct, indirect, and total effects of latent drivers (natural conditions, on-site management, agricultural development, and urbanization) on emissions. National emissions increased 2.7-fold over the study period (DEHP: from 24.29 t to 65.50 t; DBP: from 12.37 t to 33.35 t) and were strongly spatially concentrated with East China. Driver importance shifted markedly over time, with slope and rural population gaining prominence. Crucially, PLS-SEM revealed pervasive offsetting pathways: for urbanization in 2015, its direct suppressive effect on emissions (−0.195) was more than cancelled by a positive indirect effect operating through agricultural expansion (0.248), yielding a near-zero net effect (−0.015). Thus, a driver's apparent unimportance can mask large but opposing direct and indirect pathways. We conclude that greenhouse expansion simultaneously secures production and amplifies plastic pollutant emissions through a coupled driver network in which indirect mediation dominates. Because an apparently weak driver may merely be internally offset, interventions targeting a single driver are liable to be neutralized; effective control must instead act on the mediating pathways (e.g., agricultural expansion) and be differentiated by region.