Life in the oceans is remarkably resilient. After a century of over-fishing, pollution, coastal destruction and climate change, and their dramatic consequences for animal and plant life, seas and marine ecosystems could still return to their former diversity. At least come very close.

It will require a global effort. But we have the means.

A review article is an overview and analysis of the research published in a specific research field; in other words a status report of what science knows about a given topic at the time of writing.

This is the conclusion of a group of leading marine researchers from 16 universities in ten countries in a review article in the scientific journal Nature. The group is headed by Professor Carlos M. Duarte, who is employed at both Aarhus University and the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.

Efforts are working

In this review, the marine scientists have trawled through hundreds of scientific articles on how well different initiatives such as conservation and environmental protection have worked.

And they see a clear trend: Many of them work very well.

In some places, the initiatives have slowed down the speed at which animals and plants disappear, and even reversed the trend. For some species, there has actually been a spectacular improvement. For example, the number of humpback whales has increased from a few hundred in 1968 to more than 40,000 today. The population of northern elephant seal has risen from 20 breeding individuals in 1880 to more than 200,000. The sea otter in Western Canada can now being counted in thousands, while in 1980 there were just a few dozen. And in the Baltic Sea, the population of grey seals is rising.

The whales have been protected, global fishing is slowly becoming more sustainable, the destruction of habitats such as seagrass meadows and mangroves has almost ceased, and habitats are being restored.

In other words, if we stop killing life in the sea and instead protect it, life can return.

We have a choice

”Vi er nu på et tidspunkt, hvor vi kan vælge, om vi vil efterlade et modstandsdygtigt og dynamisk hav eller et uopretteligt skadet hav til de kommende generationer,” siger Carlos M. Duarte, og fortsætter:

”Vores studie dokumenterer, at marine populationer, levesteder og økosystemer er blevet gendannet i kølvandet på hidtidige bevaringsindsatser. På den baggrund kan vi nu anvise, hvordan man globalt kan opskalere de dokumenterede løsninger.”

Forskerne identificerer ni komponenter, som er afgørende for genopbygning af livet i havet: Saltmarske, mangrover, søgræs, koralrev, tang, østersrev, fiskeri, megafauna og dybhavet.

and a road map

Their roadmap includes protection of species, intelligent fisheries, conservation of marine areas, habitat restoration, less pollution and, not least, prevention of climate change.

Climate change is a particularly challenging issue, because global warming causes sea level rises and acidifies seas. Developments have already damaged tropical coral reefs so much that they can only partly be brought back to life.

"We can only restore live in the oceans if we reduce global emissions of greenhouse gases so much that we comply with the most ambitious targets in the Paris Agreement – in other words, the global temperature increase is below 1.5 °C. Otherwise, we risk wasting our energies," says Carlos M. Duarte.

The video below shows developments in protected marine areas since 1961. Note the rapid acceleration in the 21st century. Click on the two arrows in the bottom right-hand corner to see it in full size. Graphic: King Abdullah University of Science and Technology