Do Microplastics Always Harm Agroecosystem Services? A Global Synthesis

Microplastics (MPs) are an emerging global change factor with the potential to affect key agroecosystem services. Yet, MPs enter soils with highly variable properties (e.g., type, shape, size, concentration, and aging duration), reflecting their heterogeneous chemical compositions and diverse sources. The impacts of MPs with such varying properties on agroecosystem services remain poorly understood, limiting effective risk assessment and mitigation efforts. We synthesized 6315 global observations to assess the broad impacts of microplastic properties on key agroecosystem services, including crop productivity and physiology, soil carbon sequestration, nutrient retention, water regulation, and soil physical and microbial properties. MPs generally caused significant declines in aboveground productivity, crop physiology, water-holding capacity, and nutrient retention. However, the direction and magnitude of these effects varied considerably depending on the specific properties of MPs. The hazards posed by MPs to aboveground productivity, antioxidant systems, and root activity were size- and dose-dependent, with larger particles at higher concentrations inducing greater damage. Prolonged microplastic exposure impaired crop photosynthesis and soil nutrient retention, but most other ecosystem services (e.g., belowground productivity, antioxidant systems, and root activity) showed gradual recovery over time. Fiber-shaped MPs positively influenced crop aboveground and belowground productivity and soil carbon sequestration, potentially due to their linear configuration enhancing soil aggregation and connectivity. Polymer type emerged as the most prominent driver of the complex and unpredictable responses of agroecosystem services to MPs, with biodegradable polymers unexpectedly exerting larger negative effects on crop productivity, root activity, photosynthesis, and soil nutrient retention than other polymers. This synthesis underscores the critical role of microplastic properties in determining their ecological impacts, providing essential insights for property-specific risk assessment and mitigation strategies to address microplastic pollution in agroecosystems.