Where Does Plastic Really Go? New Global Model Finds Land Is the Biggest Sink

For more than a decade, the scientific conversation about plastic pollution has been dominated by a single, dramatic image: rivers carrying torrents of waste into the ocean. A new study published in the journal Environmental Challenges upends that framing. By simulating the fate of macroplastic litter across 285 of the world’s hydrological basins, researchers Catherine E. Deschênes, Martin Dorber and Francesca Verones of the Norwegian University of Science and Technology have produced the first globally consistent, spatially explicit estimates of how plastic partitions between land, rivers and lakes. Their central finding is striking: on average, 73 percent of macroplastic emitted on land never leaves it, at least within a ten-year window. The terrestrial environment, long treated as a mere staging ground on plastic’s journey to the sea, emerges as the dominant global sink.

The model, called the Global Plastic Distribution Model or GPDM, builds on a conceptual framework known as the Plastic Pathfinder, which was originally developed to simulate plastic transport in a single hypothetical basin. The research team scaled that framework up to planetary proportions by harmonizing global datasets on wind speed and direction from the Copernicus Climate Change Service, along with surface runoff, elevation and land cover from HydroSHEDS, and river networks from HydroRivers. All inputs were standardized to a common grid of 0.01 degrees, roughly one kilometer at the equator, and organized into 285 drainage basins defined by the HydroBASINS level-3 hierarchy. Eight basins, including the Caspian Sea and several small islands, were excluded because their shapes or characteristics made simulation impractical, but the discarded area represents less than half a percent of the total simulated surface.

At the heart of GPDM lies a deceptively simple physical principle borrowed from friction theory: plastic moves only when the driving forces of wind or surface runoff exceed the resistance offered by terrain and land cover. The researchers defined 61 threshold parameters governing mobilization across different land cover and slope classes. When wind or runoff surpasses a threshold, plastic is transferred to a neighboring grid cell along the wind direction or flow pathway; when thresholds are not exceeded, the plastic stays put. Each terrestrial cell receives one normalized unit of plastic at every monthly time step, a deliberate design choice that decouples environmental transport from the geography of waste generation. The result is a set of relative distribution coefficients rather than absolute mass fluxes, which is precisely what life cycle assessment practitioners need to link emissions to environmental fate.

The simulation ran for ten years at monthly resolution, long enough for the system to approach a quasi-steady state. Comparisons of outputs at three, five, seven and ten years showed limited variation after the initial period, giving the team confidence that the ten-year coefficients represent a stabilized distribution. Rivers emerged as the dominant aquatic pathway, receiving on average 20 percent of emitted plastic, with basin-level values ranging from zero to 52 percent. Lakes, by contrast, absorbed a negligible 0.19 percent on average. On land, grasslands and shrublands formed the largest sink at 24 percent, followed closely by forests at 21 percent, while agricultural and bare areas each retained about 14 percent. Urban areas, interestingly, retained almost nothing, a reflection of their smooth, impervious surfaces that offer little resistance to mobilized litter.

To test the robustness of these estimates, the team conducted a Monte Carlo sensitivity analysis across 15 basins chosen to span a range of climatic and land-use conditions. Each basin was run 100 times with lognormal perturbations of up to 20 percent applied to the threshold parameters. The results were reassuring: relative uncertainty was only 5 percent for riverine coefficients and 1 percent for terrestrial ones, though it rose to 18 percent for the small lake fraction, where tiny absolute amounts amplify proportional variability. The single most influential parameter turned out to be the surface runoff threshold governing grasslands, shrublands and agricultural plains, indicating that hydrologically driven transport, not wind, dominates large-scale plastic mobilization even though wind data were time-resolved across a decade of monthly averages.

The real test of any global model is what it reveals when confronted with real-world emission data. In a proof of concept, the researchers coupled their distribution coefficients with a comprehensive inventory of mismanaged plastic waste covering more than 50,000 municipalities worldwide. The coupled estimates suggest that of the plastic entering the environment globally each year, roughly 43 million metric tons accumulate on land, 7.17 million metric tons reach rivers, 0.31 million metric tons settle in a narrow two-kilometer coastal buffer, and only 0.12 million metric tons end up in lakes. Country-level rankings varied dramatically by compartment. India ranked first in most terrestrial categories and in lakes, but only third in grasslands and second in rivers. Indonesia topped the riverine transfer ranking, consistent with its vast network of river cells, while Nigeria led in grassland accumulation despite more modest showings elsewhere.

These compartment-specific rankings carry a powerful policy implication: the countries contributing most to terrestrial pollution are not necessarily the same ones driving riverine or coastal accumulation. A nation’s plastic footprint, in other words, cannot be captured by a single number. The authors argue that this argues for regionalized fate factors in environmental assessment rather than one-size-fits-all global averages. Their comparison with the published literature showed broad agreement for freshwater compartments but estimates one order of magnitude higher for terrestrial and coastal accumulation than most existing assessments, a divergence the researchers attribute to their explicit representation of environmental retention rather than a narrow focus on ocean inputs.

The model is candid about its limitations. It treats all macroplastic as a generic, undifferentiated unit, using mobilization thresholds originally derived from loose paper, which are more representative of lightweight items like bags and bottles than of heavier or denser objects. It excludes sinking, deposition, sedimentation, fragmentation and the conversion of macroplastics into microplastics. Narrow rivers smaller than the one-kilometer grid resolution are not explicitly represented, likely underestimating transfers to small streams. Extreme events such as floods and monsoons, known to dramatically amplify plastic mobilization, are not captured, nor are dams and reservoirs that act as retention structures. The outputs were not calibrated against field observations, partly because relative basin-level fractions cannot be directly compared with absolute point measurements. Coastal zones posed a particular challenge, with spatial bias detected near the Ganges estuary in Bangladesh and the Caspian coastline near Sumqayit in Azerbaijan, prompting the researchers to introduce the two-kilometer coastal buffer in their country-scale analysis.

Despite these caveats, the significance of the work is hard to overstate. Life cycle assessment, the standard tool for evaluating the environmental footprint of products, has long suffered from a blind spot: while characterization factors exist for marine microplastics and for macroplastic entanglement and ingestion at sea, comparable factors for terrestrial and freshwater macroplastic impacts have been missing entirely. Most existing fate models simply assume that macroplastics do not move after being emitted to land. GPDM demolishes that assumption by quantifying, basin by basin, the probability of cross-compartment transfer. The model’s code and raw spatial outputs are openly available on Zenodo, allowing other researchers to couple the coefficients with their own emission inventories or process-based models.

Perhaps the deepest message of the study is conceptual. By demonstrating that land is the primary global sink for macroplastic waste, GPDM shifts the analytical center of gravity away from the ocean-centric narrative that has defined the field since the earliest global estimates of plastic inputs to the sea. Plastic that lingers in soils, forests and grasslands is not harmless; it fragments, leaches chemicals, enters food webs and degrades ecosystems in place, and it can be remobilized by floods or storms years or decades later. As negotiations toward a global plastics treaty continue, the study suggests that waste management interventions on land, particularly in low-income countries where uncollected waste and open dumpsites drive emissions, may deliver far greater environmental returns than previously appreciated. The missing plastic, it turns out, was never really missing. It was hiding in plain sight, scattered across the landscapes we live in.

Subject of Research: Global spatially explicit modeling of macroplastic distribution from land into terrestrial, riverine and lake compartments

Article Title: A Global Basin-Delineated Model of Macroplastic Distribution from Land to Aquatic Environments

Article References: Deschênes, C. E., Dorber, M., & Verones, F. (2026). A Global Basin-Delineated Model of Macroplastic Distribution from Land to Aquatic Environments. Environmental Challenges, 25, Article 101672. https://doi.org/10.1016/j.envc.2026.101672

Image Credits: AI Generated

DOI: Not provided

Keywords: plastic pollution, macroplastics, global model, river basins, terrestrial sink, life cycle assessment, hydrology, land cover, mismanaged plastic waste, environmental fate, freshwater, sustainability