A research group led by Prof. DANG Fei from the Institute of Soil Science of the Chinese Academy of Sciences, in collaboration with Prof. ZHONG Huan from Nanjing University, has uncovered a significant yet often overlooked consequence of microplastic pollution: its detrimental impact on photosynthesis-a critical process underpinning Earth's primary productivity and food security.
The study, recently published in PNAS, provides a comprehensive evaluation of the relationship between microplastic exposure and photosynthesis across terrestrial, marine, and freshwater ecosystems.
Microplastics-defined as plastic debris smaller than 5 mm-contaminate environments from deep-sea sediments to mountain glaciers. Despite growing awareness of this environmental hazard, the effects of microplastics on photosynthesis at the ecosystem level have remained unclear.
Previous studies have produced fragmented or contradictory results due to ecosystem complexities, differences among affected photoautotrophs (e.g., plants and algae), and the diverse nature of microplastics themselves. This knowledge gap poses a significant challenge to global efforts to achieve the United Nations (UN) Sustainable Development Goals (SDGs), particularly the Goals of Zero Hunger (#2), Good Health and Well-being (#3), Responsible Consumption and Production (#12), and Life Below Water (#14).
By analyzing 3,286 records using meta-analysis and machine learning techniques, the researchers quantified the global decline in photosynthesis due to microplastic exposure. Their findings reveal that microplastics decrease photosynthetic efficiency by 7.05-12.12% across terrestrial plants, marine algae, and freshwater algae. These reductions translate to estimated annual global losses of 4.11-13.52% (109.73-360.87 MT·yr-1) for key staple crops such as rice, wheat, and maize.
In aquatic ecosystems, microplastic-induced photosynthesis inhibition is projected to cause net primary productivity (NPP) losses of 0.31-7.24% (147.52-3,415.11 MT C·yr-1), leading to seafood production declines of 1.05-24.33 MT·yr-1. These figures underscore the hidden yet profound threat that microplastic pollution poses to global food security.
Encouragingly, the study suggests a pathway for mitigation. The researchers estimate that a 13% decrease in environmental microplastic levels could reduce photosynthesis losses by approximately 30%, preventing global losses of 22.15-115.73 MT·yr-1 in major crops and 0.32-7.39 MT·yr-1 in seafood production.
The findings highlight the urgent need to address microplastic pollution as a critical factor affecting global primary productivity. The study emphasizes the importance of incorporating plastic pollution mitigation strategies into broader sustainability and food security initiatives. It also calls for greater data collection and publication on the extent and mechanisms of microplastic-induced photosynthesis disruptions in future field studies.
As more high-quality field data and advancements in remote sensing technologies become available, researchers can refine their understanding of this emerging threat. These insights can then inform international plastic treaty negotiations and support efforts to achieve the UN SDGs.
Global maps of annual production losses for three main food crops (Image by DANG Fei)
A conceptual framework that allows the continual updating of data input to ameliorate our model's precision and accuracy (Image by DANG Fei)
