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Large quantities of plastics flow from rivers to estuaries, where they potentially converge in frontal zones. This Perspective describes the occurrence, transformation and impact of these processes, highlighting their importance in mitigating plastic pollution.
Atmospheric transport of microplastics could be a major source of plastic pollution to the ocean, yet observations currently remain limited. This Perspective quantifies the known budgets of the marine-atmospheric micro(nano)plastic cycle and proposes a future global observation strategy.
The size and shape of alluvial river channels control and adjust to the flow of water and sediment, with consequences for flooding and ecological habitat. This Perspective examines how the sediment entrainment threshold constrains the size, shape and dynamics of alluvial rivers.
The planetary boundaries framework outlines a safe operating space for humanity according to key Earth system dynamics. This Perspective proposes the addition of a green water planetary boundary based on root-zone soil moisture and demonstrates that widespread green water modifications now present increasing risks to Earth system resilience.
