Studland Bay is an unlikely battleground. The sandy shore, part of England’s southern coastline, is both a beauty spot and the site of “the most popular naturist beach in Britain”. More importantly for Nature-ists, the seagrass that thrives in the bay’s shallow waters is home to rare sea-horse populations. But keeping it that way is a growing challenge, because Studland is also a playground for the wealthy and powerful, including some yacht-club members who like to anchor their boats there, to the possible detriment of the natural habitat.

Scientists can make the case for conservation, but the value of marine sites such as Studland is hard to sell. It is not the Great Barrier Reef with its miles of coral, or the Galapagos Islands and their sharks, turtles and marine iguanas. It is not even Lundy — the island at the centre of the first UK marine park, home to seals and puffins.

Last week, the UK government ended a public consultation on the latest round of its attempts to manage conflicts between conservation and other maritime interests. Officials plan to create dozens of marine conservation zones (MCZs) around the UK coast, to introduce an extra level of protection for worthy sites. The move is part of a global effort to extend conservation measures on land to the coast and open seas.

But, as on land, conservation of marine areas is not popular with every­one, and the ambitious UK plans are in danger of running aground. Already, proposals for the Studland MCZ have been dropped for now, and plans for others are in danger. In fact, marine experts who originally identified 127 sites for MCZs around the British coastline now fear that, in the worst case, barely more than half will be realized.

The UK process sets up these zones in three waves. The first saw 31 proposed MCZs reduced to 27, which were designated in November 2013. A second tranche of designations initially featured 37 sites, but was whittled down to 23 even before the public consultation closed last week. (Studland Bay MCZ was one of the 14 that were chopped.) The third wave is meant to be set up before 2016.

The United Kingdom is squaring up for a general election on 7 May, and even long-serving politicians are nervous about keeping their seats. Marine conservation is low on the agenda — especially the sort that annoys boat-owning voters. But the next government will have to take some tough decisions on marine protection. Because of the way the first two tranches of MCZ designation have progressed, the third will be left with difficult decisions on controversial sites that have been kicked into the long (sea)grass by the earlier rounds. These include not only Studland but also the important deep-water mud habitats of the Celtic Deep, and another sea-horse habitat off the Isle of Wight.

The UK government deserves credit for establishing the parks at all.

Crucially for the United Kingdom, failures at home are undermining its potential to show global leadership on marine conservation. Huge marine parks have been designated around UK territories such as the Chagos Islands in the Indian Ocean, and another was announced on 18 March for the Pitcairn Islands in the south Pacific. Significant questions remain over enforcement and monitoring of these overseas reserves, and must be solved if they are not to become what scientists call ‘paper parks’ — just a line on a map rather than something that does any good.

But the UK government deserves credit for establishing these parks at all. This is despite a recent setback for the Chagos reserve — a judge ruled last month that the park had been improperly declared by Britain because Mauritius, which has fishing rights in the archipelago, had not been fully consulted.

Later this year, the finalized United Nations Sustainable Development Goals are likely to include a commitment to protecting the oceans. Making good on this and on existing promises will require governments to disappoint some powerful vested interests that would prefer to keep access to marine areas unrestricted. And if rich nations wish to push the rest of the world to protect its marine wonders, they must first get their own houses in order. Scientists can help by promoting the value of places that lack the brand recognition of the Great Barrier Reef. If the world’s seas are really going to be protected, mud and seagrass will have to be considered alongside tropical reefs.