Callum Roberts's Blog

Our guest scientists pick the breakthroughs and discoveries that defined their year, from insights into human evolution to our first trip aboard an asteroid

Take a deep breath. Dive into the emerald water. It’s 13 minutes and 70 metres down to lunch. Are you dead yet? Not if you are one of the Bajau “sea nomads” of south-east Asia, who have been free-diving like this for more than 1,000 years, relying on their remarkable physiology, and, as we learned in April, their genes. Humans left Africa 50 millennia ago, encountering new environments that required adaptation to survive. Adaptation is mostly cultural – building shelters, using fire, deciding what to eat, and transmitting instructions from generation to generation. But alongside this are advantageous genetic mutations grasped by natural selection.

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Leading scientists pick the dozen most significant discoveries and developments of 2017 – from a steep decline in flying insects to a virus that can kill bacteria

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America’s addiction to cheap meat, fed on corn and soy in vast indoor factories, comes at a high cost to our own health and that of the planet

Callum Roberts is professor of marine conservation, at the University of York, UK

Every spring, as the snows thaw, water rushes down the Mississippi and Missouri rivers, spreading life, then death into the Gulf of Mexico. The floodwaters are laden with fertilisers washed from fields and factory farms. As spring turns to summer, excessive nutrients first drive a huge bloom of living plankton, then cause death on a gargantuan scale as a dead zone blossoms across the seabed. Most years it grows swiftly to over 5,000 square miles of seabed, killing everything that cannot outrun it.

Related: Why meat eaters should think much more about soil | John Sauven

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While we can celebrate the North Sea cod’s revival we can only achieve sustainability with fishing methods that are less destructive to the ecosystem

• Callum Roberts is professor of marine conservation at the University of York

News that North Sea cod has made a comeback has been welcomed by fishermen, environmentalists and fish and chip lovers. After decades of overfishing, cod reached its nadir in 2006. By then, stocks were less than a fifth of levels seen in the early 1970s, and only a third of the size needed for long-term sustainability. This year stocks finally climbed back above the threshold for maximum sustainable yield, which means cod should be back on the menu for good.

Related: Sustainable British cod on the menu after stocks recover

Incredibly, nearly all the English marine protected areas still allow bottom trawling and dredging for scallops

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Jut when we need it most, the very future of seafood is in doubt. How did the official figures get it so wrong – and can anything be done before it’s too late?

About 164,000 years ago, people living in a South African coastal cave discovered the joy of seafood. Discarded marine snail shells deeply buried in the muck of human habitation represent the first evidence of seafood dinners. From then on, the increasing presence and richness of archaeological remains, and historical evidence, testify to our deepening love affair with seafood.

Related: Fish stocks: Good news is a drop in the ocean | Editorial

Related: Overfishing is a solvable environmental challenge for the EU | Aniol Esteban

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A definitive study released last week found that the amount of wildlife in our oceans has fallen by half in 45 years. Academic and marine expert Callum Roberts says there is still time to reverse this decline by closing areas to fishing

Sardines were once extraordinarily abundant in the south-west of England, leading one 19th-century guidebook to say: “Pursued by predaceous hordes of dogfish, hake and cod, and greedy flocks of seabirds, they advance towards the land in such amazing numbers as actually to impede the passage of vessels and to discolour the sea as far as the eye can reach … Of a sudden they will vanish from view and then again approach the coast in such compact order and overwhelming force that numbers will be pushed ashore by the moving hosts in the rear. In 1836 a shoal extended in a compact body from Fowey to the Land’s End, a distance of at least 100 miles if we take into consideration the windings of the shore.” (Handbook for Travellers in Devon and Cornwall, John Murray and Thomas Clifton Paris, 1851).

Today people travel thousands of miles to dive and film such scenes, not realising they were once commonplace on our own coasts. Last week the World Wide Fund for Nature and the Zoological Society of London issued their most comprehensive look at the state of life in the sea. The report makes uncomfortable reading. Taking in more than 1,000 species worldwide and 5,000 populations of fish, turtles, marine mammals and a host of others, it draws the bleak conclusion that there is only half the amount of wildlife in the sea today as in 1970.

We no longer fish commercially for species such as common skate because there are hardly any left

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Marine conservation policy has drifted far off its original course but there is still a way to save our seas

0.000001 one hundred thousandth is a number so small that to most people it seems like nothing at all. Yet four and a half years since the Marine Act of 2009 came into force legislation that was heralded as the saviour of UK seas this is the sum total of UK waters that is protected from all fishing for the purpose of nature conservation.

The Marine Act is that rare thing: a law supported by all political parties. The sea is dear to so many of us it transcends ideology. In the run up to the law's enactment, there was widespread recognition that the seas were in trouble. Fisheries were in decline, once rich habitats had been stripped by two centuries of destructive fishing, and formerly abundant species had been brought to the verge of disappearance. Five such endangered species are featured on a set of stamps issued this month by the Royal Mail: sturgeon, common skate, spiny dogfish, conger eel and wolffish. There are dozens more.

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Hugh Fearnley-Whittingstall rightly criticises fishing practices but a discard ban must be joined by other tough measures

Hugh Fearnley-Whittingstall has set his sights on several of the fishing industry's dirty secrets in a series aired this week on Channel 4's three-part Big Fish Fight series. The first programme looked at the practice of discarding, whereby fishermen are compelled by EC rules to throw away perfectly good fish that they have no quota for, while pursuing fish that they do. The images of basket after basket of wholesome fish flung back dead were powerful and disturbing, and Fearnley-Whittingstall was right to shine a spotlight on this disgraceful practice.

An EU plan to pay fishermen to catch plastic will help save our waters from waste while providing fleets with alternative income

Rarely has a TV campaign been won so convincingly. In January this year, Hugh Fearnley-Whittingstall's Fish Fight programme persuaded over 600,000 of us to support a ban on the wasteful practice of throwing dead fish back into the sea. The European commission listened and has announced it intends to ban discarding fish.

Only now with the launch of the Global Ocean Commission are we finally addressing the ravages of the oceans

The oceans are changing faster today and in more ways than at any time in human history. We are the cause. Which is why I welcome the launch of the Global Ocean Commission, dedicated to ending the neglect, in international affairs, of the high seas. These seas lie far beyond the horizon 200 nautical miles offshore to be precise and begin where sovereign national waters give way to the global commons, owned by none, shared by all.

There was a time when foreign travel gave many people a familiarity with the high seas. Rather than a few hours in a plane, "long haul" often meant days or weeks spent staring at an endless canvas of sea and sky. Today, few of us know much about what happens beyond the horizon and still fewer care. Like all common spaces, the high seas are vulnerable to misuse and abuse. Our indifference is costing the world dear for the high seas are being plundered.