Populations of gannets, puffins and other marine birds are in freefall, but a crucial scientific study to pinpoint the causes is being blocked, say experts

Bempton Cliffs bird reserve was in fine fettle last week. The last of its population of puffins had departed for the winter a few weeks earlier, while its thousands of young gannets were still being cared for by their parents on the chalk cliffs of the East Yorkshire nature site. For good measure, kittiwakes, cormorants and fulmars were also bathing in the sunshine.

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It was a comforting sight for any birdwatcher but this benign picture was in stark contrast to many other bird reserves in Britain. Our populations of seabirds – arctic skuas, arctic terns and kittiwakes – are in freefall. And, in some cases, the numbers are dire.

“For reasons that are not entirely clear – though they are almost certainly concerned with climate change – Bempton Cliffs has not suffered from the precipitous declines in seabird numbers that we see elsewhere,” said Euan Dunn, a principal policy officer for the RSPB.

“Our seabird colonies, especially those in northern Scotland, are withering away. At the same time, the government has displayed a complete dereliction of duty in failing to properly track this calamity. In particular, it has ignored calls to carry out its statutory duty to organise a comprehensive national census of our seabirds, even though one is long overdue. That would at least reveal the extent of the crisis and help highlight possible solutions.”

Until we have the whole picture, which only a comprehensive census can provide, we cannot work out how to stop the rot Euan Dunn, RSPB

One example of the devastating losses is found on St Kilda, one of the most significant seabird colonies in the North Atlantic. On this rocky outpost, there has been a 99% reduction in kittiwake nests since 1990. Last year only one pair bred in all the monitored sites on the island, and that single chick died. Yet in the middle of the last century these distinctive dark-eyed gulls thrived across the island. In addition, the kittiwake colony at Marwick Head on Orkney was once a noisy, bustling home to thousands of kittiwakes but is today deserted.

Similarly, Fair Isle puffins, with their large pale cheeks and brightly-coloured bills, have dropped in numbers from 20,000 to 10,000 over the past 30 years, while on Orkney and Shetland guillemots have also halved in number with several colonies disappearing. Fulmars, arctic skuas and arctic terns have also suffered massive losses. Added together, these statistics indicate that, in the past 25 years, Scotland may have lost almost half its breeding seabird population.

Facebook Twitter Pinterest Britain is an internationally important site for puffin colonies, yet their numbers are also plummeting. Photograph: Murdo Macleod/The Guardian

A catastrophe is unfolding. The UK is an internationally important site for seabirds, is home to most of the world’s Manx shearwaters, gannets and great skuas, and has significant colonies of many other key seabirds such as the Atlantic puffin. Yet the government has resolutely declined to fund a new national census in the wake of those organised in 1970, 1985 and 2000 and which it is supposed to instigate every 15 years.

“It’s a lamentable failure of government not to have given its statutory nature conservation agencies the resources necessary to carry out a coordinated comprehensive national census of our seabird colonies,” said Dunn.

When the first national census –known as Operation Seafarer at the time – was completed in 1970, populations of seabirds appeared fairly healthy, as did those that were counted for the second national census in 1989. However, the census of 2000 produced worrying evidence that declines were taking place. “Things have got much worse since then. We are supposed to have a national census every 15 years but now that is slipping towards 20 years – just at a time when populations of so many seabirds are clearly in freefall,” said Dunn.

“We desperately need to have an accurate assessment of what is going on, a census that will pinpoint the varying fortunes of all our colonies and which will tell us where we may need to bolster particular sites and build resilience.

“We may need to establish marine protected areas offshore or take action to rid an island of rats. But until we have the whole picture, which only a comprehensive census can provide, we cannot work out where to deploy our resources.”

As to the possible causes of the dramatic decline in seabird populations, most experts point to the waters around the UK that have increased in temperature by more than 1C thanks to global warming caused by rising greenhouse gas emissions. In the wake of this change, seas have also seen a dramatic loss of zooplankton while, further up the food chain, sand eels – a critically important source of food for many birds – have disappeared from many parts of the Atlantic and the North Sea. As a result, seabirds such as terns and kittiwakes – which only take sand eels from the sea surface – are doing far worse than birds such as razorbills, which take fish from greater depths.

“The trouble is that climate change is only going to worsen,” said Dunn. “We desperately need to do something to give our seabirds a fighting chance of survival in future. The very least we can expect to achieve that is a proper census every 15 years.”