The UK now protects 38% of its seas by law. Yet the government’s own assessment shows that our oceans are not thriving.

In April, the Department for Environment, Food, and Rural Affairs (Defra) published its latest assessment of the health of our seas: the UK marine strategy report.

Of the 15 components of ocean health assessed, only two clearly meet the standard of good environmental status (GES) – the benchmark for healthy seas that the UK committed to achieving by 2020. The other 13 are failing, uncertain or getting worse.

This is despite the UK now having 377 marine protected areas (MPAs), sections of sea designated by law to protect wildlife and habitats. Protected areas are important, but the detail behind that impressive-looking map is sobering.

Marine mammals, such as Whales, dolphins, and porpoises are not judged to have achieved good status. A key reason for this is bycatch: they are being accidentally caught and killed in fishing nets meant for other species.

Seabird populations are declining, with fewer chicks surviving each breeding season as the fish they depend on become harder to find.

The types of fish living in our seas are changing for the worse, with the biggest cod disappearing while smaller species take their place.

The entire food web is under strain. The microscopic organisms that underpin ocean life, called plankton, are becoming less productive as seas warm, and that loss ripples upward through every species that depends on them.

On the seabed, fragile habitats such as seagrass meadows continue to be damaged by pollution and disturbance from shipping and boat activity.

Our seas are getting noisier, more polluted with heavy metals, and littered with waste on the seafloor.

There are some bright spots. The numbers of grey seals are stable or increasing. Beach litter is declining. Commercial fisheries have shown modest improvement, with the share of fish stocks being fished at sustainable levels rising, though it is still fewer than half.

But these gains are outweighed by the broader trajectory.

Why MPAs are not enough

Protected areas play an important role, but they cannot address the full range of pressures our seas face. Drawing a boundary on a nautical chart does not stop warm water crossing it. It does not filter out the nutrient runoff flowing in from agricultural land and overwhelmed sewage systems. It does not silence the increasing underwater noise from shipping and industrial activity. It does not prevent whales, dolphins and porpoises from being caught in fishing gear that operates both inside and outside these boundaries.

Climate change is perhaps the telling example. Sea temperatures around the UK have risen by roughly 0.3°C per decade over the past 40 years, with extreme underwater heatwaves becoming more common. The report acknowledges that this is already altering marine ecosystems, affecting everything from plankton at the base of the food chain to the distribution of fish species. No MPA can insulate its inhabitants from a warming ocean.

Land-based pollution is another pressure that flows straight through protected area boundaries. The report identifies food production and sewage treatment as major causes of nutrient enrichment, with increasing nitrogen inputs entering coastal waters. Heavy metals from legacy mine contamination, particularly in Wales, continue to pollute the marine environment. Contaminants have not met good status because lead, mercury, copper and zinc remain above environmental thresholds.

What ocean recovery actually requires

None of this is an argument against marine protected areas. Well-managed MPAs are an essential tool, and recent proposals to ban bottom trawling in some protected sites are welcome.

But if we are serious about ocean recovery, we need to tackle root causes. That includes reducing agricultural and urban runoff and sewage discharges into rivers and coastal waters. The climate crisis is reshaping our marine ecosystems from the bottom of the food chain upwards so tackling greenhouse emissions is a key step. Managing underwater noise from an increasingly industrialised seascape is essential. And enforcing meaningful fisheries management will reduce bycatch and protect whole ecosystems, not just commercial stocks.

The government’s own environmental watchdog, the Office for Environmental Protection, has reached a similar conclusion. In September 2025, it identified possible serious failures by Defra to comply with environmental law in relation to the missed GES target, and launched a formal investigation. It is now asking the government to produce an evidenced, resourced and time-bound delivery plan.

When even the body set up to hold government to account on the environment is questioning whether the law has been broken, it is hard to argue that the current approach is working.

The UK was supposed to have achieved good environmental status in our seas by 2020. Six years past that deadline, this report shows we are still far from it. We cannot afford to let the percentage of protected areas on a map be a substitute for the hard and messy work of actually making our oceans healthy.

Heidi McIlvenny receives funding from the National Environment Research Council, the Department of Agriculture, Environment and Rural Affairs, and Ulster Wildlife. She is affiliated with the IOLN, RSPB, National Trust, and Ulster Wildlife.