From pollution to overfishing to the escalating effects of climate change, human activities are placing mounting pressure on the world ocean, fueling what U.N. Secretary-General António Guterres describes as a “deepening crisis.”
Those warnings are detailed in the third U.N. World Ocean Assessment, released June 8 and authored by approximately 600 experts from 86 countries. Covering the period between 2021 and 2025, the report echoes concerns raised in the U.N.’s earlier World Ocean Assessments, published in 2015 and 2021, which describe a global ocean under immense strain due to human-driven pressures.
The authors point toward progress in ocean governance through a review of 57 global treaties related to ocean protection, including the recently ratified high seas treaty, known more formally as the marine biological diversity of areas beyond national jurisdiction (BBNJ) agreement. However, they caution that existing frameworks generally remain “fragmented” and cannot fully address the scale of the challenges facing the ocean. Even so, the authors argue that it is imperative to continue strengthening conservation efforts, regulations and international cooperation to mitigate the damaging impacts of human activities and preserve marine ecosystems.
“The imperative for a healthy and resilient ocean has never been more urgent,” Rafael González-Quirós, director of the Oceanographic Centre of Gijón, Spain, who played a key role in coordinating the report, said in a press release. “Global collaborations and research, and our increased understanding of the ocean, provide essential insights into the state of marine ecosystems, the profound changes they are undergoing and the need for our care.”
One of the report’s main findings is that ocean warming is happening at an accelerated pace, with approximately 16% of the overall warming measured since 1955 having occurred in just the past eight years. While warming can cause a range of marine issues, from algal blooms to coral bleaching and extreme weather events, it also contributes to rising sea levels. According to the report, the rate of sea level rise more than doubled in the last 10 years, going from less than 2.0 millimeters (about 0.1 inches) per year before 2015 to 4.3 mm (about 0.2 in) per year in 2023.
It also highlights the ongoing issue of plastic pollution: 52.1 million metric tons of plastic waste enters the ocean each year, impacting more than 4,000 marine species, including sea turtles and seabirds.
The assessment points out that many knowledge gaps remain, including what we know about deep-sea habitats and biodiversity. For instance, it notes that only 27.3% of the seafloor has been mapped as of 2025, and that there is a “a lack of knowledge about deep-sea species,” which remain vulnerable to fishing activities such as trawling. The report also calls deep-sea mining an “increasing potential threat” that could destroy habitats and harm biodiversity and says the “timescales of recovery and species-specific responses” to this activity “remain an important knowledge gap.”
There is also an emphasis on the interconnectedness of ocean health and human well-being in the report, which details how food security, livelihoods, cultural identity and economic prosperity depend on a healthy, functioning ocean. For instance, the report notes, small-scale fisheries employ more than 60 million people and produce more than 25 million metric tons of food each year. Yet at the same time, it points out, coastal Indigenous peoples and local communities who depend on the ocean are often marginalized and lack secure access to resources and participation in governance.
The assessment stresses the importance of Indigenous, traditional owner and local community knowledge, saying that ocean governance models that incorporate this knowledge are “more likely to achieve comprehensive marine ecosystem and well-being outcomes.” For instance, it notes that the consultation of Indigenous peoples and traditional knowledge holders has been embedded in processes such as the International Maritime Organization, which recently granted observer status to the Inuit Circumpolar Council, an organization representing about 80,000 Inuit across Alaska, Canada, Greenland (Kalaallit Nunaat) and Chukotka.
Speaking at a U.N. press conference on June 8, World Oceans Day, that marked the release of the report, aquanaut and ocean conservationist Fabien Cousteau stressed the “urgency” of the challenges facing the global ocean, which he said supports “all life that we know, that we cherish and that we depend on.”
Yet Cousteau said the third U.N. World Ocean Assessment outlines the tools needed to “implement the beginnings of solutions” and “change the course we’ve set for ourselves.”
“It’s no time to give up,” Cousteau said, “and it’s certainly no time to go silent.”
Banner image: Wild bottlenose dolphins in the New York Bight. Image courtesy of Chris St Lawrence/American Princess Cruises.
Elizabeth Claire Alberts is a senior staff writer for Mongabay and was a 2024-2025 fellow with the Pulitzer Center’s Ocean Reporting Network. Find her on Bluesky and LinkedIn.
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