Monitoring agricultural plastic film use and residue generation through remote sensing techniques
- Annual plastic production is approaching the mass of the world population. Its durability, low cost, and versatility have driven this success. However, these same properties, combined with poor waste management, have made plastic a persistent and ubiquitous environmental contaminant: at least 80% of all plastic ever produced is estimated to remain in the environment.
Soils are estimated to be a larger sink for plastic than the ocean surface, with agricultural soils representing a major sink and source of plastic. Plastic has become an integral component of modern agriculture, encompassing a wide range of on-field applications. In European vegetable production, around 80% of plastic use is attributed to crop cover films. Globally, plastic films may cover an area larger than the United Kingdom.
Plastic films have been improving crop production, providing benefits for both consumers and producers. However, these benefits come at the cost of potential soil contamination with plasticAnnual plastic production is approaching the mass of the world population. Its durability, low cost, and versatility have driven this success. However, these same properties, combined with poor waste management, have made plastic a persistent and ubiquitous environmental contaminant: at least 80% of all plastic ever produced is estimated to remain in the environment.
Soils are estimated to be a larger sink for plastic than the ocean surface, with agricultural soils representing a major sink and source of plastic. Plastic has become an integral component of modern agriculture, encompassing a wide range of on-field applications. In European vegetable production, around 80% of plastic use is attributed to crop cover films. Globally, plastic films may cover an area larger than the United Kingdom.
Plastic films have been improving crop production, providing benefits for both consumers and producers. However, these benefits come at the cost of potential soil contamination with plastic residues. Laboratory experiments using very high concentrations of a limited range of plastic types raise serious concerns, e.g. regarding the ecotoxicological effects of plastic residues. Despite this growing concern, the implications of current plastic contamination levels remain poorly understood, partly because of limitations in environmental monitoring techniques. Field-scale monitoring lacks the required speed and consistency to monitor residue generation, while large-scale monitoring lacks a scientifically rigorous, spatially explicit approach for monitoring plastic film use. This thesis exploits remote sensing techniques to fill this gap.
Chapter 2 lays the foundation for the use of UAVs (unmanned aerial vehicles) in mapping plastic film residues on agricultural soils. The combination of laboratory and field experiments demonstrates that current technologies may be limited to case-dependent methodologies. At the same time, the results highlight the strong potential of advances in sensor technology to enable not only the monitoring of plastic films but also broader monitoring of soil plastic contamination. Within this framework, the first available spectral library of agricultural plastic films was created, enabling future efforts to develop algorithms and sensors for mapping plastic film residues on agricultural soils.
Chapters 3 and 4 build on the advanced status of satellite-based mapping of agricultural plastic films to develop scalable monitoring workflows using free and open data within a cloud computing environment. Chapter 3 leverages the broad spatial coverage of satellite data to map plastic film use across Germany in 2020, showing that plastic films cover approximately 140,000 hectares and identifying the regions where this practice is most prevalent. Chapter 4 extends this workflow to capture bi-weekly plastic film dynamics in North Rhine-Westphalia from 2020 to 2022. The analysis demonstrates that satellite-based mapping can also provide detailed temporal insights and reveals that plastic film use is highly heterogeneous, not only across space but also over time.
Monitoring plastic film use at large scales with high temporal frequency offers multifaceted value. On the one hand, when combined with field-scale quantification of plastic residues, such as the UAV-based method described in Chapter 2, these data products allow for estimating potential inputs of plastic film residues across large areas. On the other hand, spatially explicit and temporally resolved maps of plastic film use open opportunities to investigate previously underexplored research questions, such as the effects of plastic film use on soil erosion, plastic transport, and hydrological processes.
Overall, this thesis presents transferable, actionable approaches for integrating remote sensing into a broader framework for plastic film use risk assessment. Research has so far mainly focused on contamination by plastic particles smaller than 5 mm, while the relative ease of collecting data on macroplastic contamination — particles bigger than 5 mm — has not been fully exploited. Remote sensing has the potential to bridge this knowledge gap and open new research directions, such as understanding the impact of plastic film use on landscape processes.…
