Removing plastic benefits marine ecosystems: Evidence from four decades of endangered seal entanglement

Abandoned, lost, or otherwise discarded fishing gear (ALDFG) causes tremendous harm to marine species and ecosystems. To mitigate the destruction wrought by these ocean plastics, various cleanup programs have been established, though benefits of such efforts to marine species and ecosystems have not been demonstrated. We examined over 40 years of Hawaiian monk seal marine debris entanglement records before and after large-scale marine debris removal efforts were initiated in the Northwestern Hawaiian Islands, demonstrating a significant reduction in entanglement rate where debris removal effort was most concentrated. Large-scale and sustained removal of ALDFG meaningfully benefits marine ecosystems and has the potential to be transformational in restoration efforts.

Methods
These data are based on tagging and visual monitoring of weaned Hawaiian monk seal pups in the Northwestern Hawaiian Islands, including observed incidents of entanglement in marine debris. The data were processed to calculate a robust rate of entanglement for comparison among populations and years. Poisson regression analyses were then used to determine factors, including the effect of large-scale marine debris removal, on the entanglement rate. Information on the timing, location, and amount of marine debris removed from islands and marine habitats were also summarized.