Nature.org asked Spalding exactly what these findings mean for the ocean and coastal resources upon which much of the world depends — and if there's anything we can do about their degradation.
"We need to start placing demands on our leaders to call for better management of our oceans."
Mark Spalding, Nature Conservancy scientist
Just how much are humans affecting oceans?
Our impact is everywhere. When we look out across the ocean, it's tempting to imagine that it's still a vast wilderness, a final frontier where humans have little impact.
In reality the oceans are vulnerable, particularly in coastal waters — hard up against a great storm of human disturbances. But they are also vulnerable far from land, where fishing fleets are extracting all they can.
There's been a lot of attention on oceans lately. How is this report different?
The report stands out because it captures the combined impact of major threats to the oceans — such as overfishing, pollution or invasive species — and how they affect different ecosystems such as coral reefs or mangrove forests. It's the first comprehensive review.
It is often not single impacts that cause problems, but a nasty concatenation. For example, a torrent of impacts has affected the Caribbean coral reefs, wave on wave: pollution, overfishing, coral bleaching and diseases. Although still beautiful and fairly productive, most of the Caribbean coral reefs are a shadow of their former selves.
Conservation on land has a long history and has captured the public imagination for decades, but in the oceans we have done very little. In many ways it seems the challenges for ocean conservation are far greater.
I think what we're seeing is a small degree of re-balancing as conservation scientists are realizing just how much we need to do to try and sustain oceans — the largest ecosystems on Earth.
What are the most affected areas of the world's oceans? And which human activities seem to be causing the most damage?
Not surprisingly, the worst affected oceans are those that touch densely populated coastlines. We're talking about the northern Atlantic — both on the U.S. seaboard and more especially around northern Europe — and the western Pacific around Japan, Korea, China and into Southeast Asia.
But just as important in many ways is the unequivocal spread of human impacts across the high seas.
Unsustainable levels of fishing are a major driver of these problems. Despite increasingly complex equipment and the opening up of new fisheries year on year, total fish catches around the world are stable or declining, and have been for a number of years.
The crazy part is that if we could only collectively get our act together and properly manage our fisheries, we could allow sufficient recovery and enable higher fish catches for less effort and leave our ecosystems in a better place to adapt to other impacts.
Coastal waters are of course are greatly impacted by pollution. Nutrients are a major problem — they wash off the land, from human and animal waste and from agricultural fertilizers, and encourage algal blooms that block out light from the seabed. Or they produce toxic algae that are ingested by shellfish, making them a hazard to humans.
And in extreme cases, such as in the waters off the Mississippi River, the blooms suck oxygen out of the water, leaving a dead zone the size of New Jersey where no fish can live.
Is there any hope that the oceans can be rehabilitated? What would we have to do, or stop doing, to help the oceans and ocean habitats repair themselves?
The big picture can seem pretty gloomy, but we need to keep a sensible perspective. At large scales, the map points us to areas that still have a relatively low impact — surely targets to try and prioritize urgent and large-scale conservation efforts that could include large protected areas, regulations to ensure that fisheries are fairly and sustainably managed, coastal development plans to prevent pollution, and shipping and aquaculture controls to prevent the damaging release of invasive species, to name a few.
Fantastic work is also going on all around the globe, perhaps especially in some of the heavily impacted areas that show us that nature can and will bounce back if we give it the space.
Hundreds of protected areas and no-take fishing areas are undergoing remarkable recoveries, supplying larvae and adult fish to adjacent waters. New efforts at restoring salt marshes, shellfish beds and mangrove forests are beginning to pay dividends in providing a whole array of services not only to natural systems, but also to coastal populations.
I really don't think there can be one top priority. Instead, there's a raft of problems and dozens of tried and tested methods to deal with them. The Conservancy is already a world-leader in some innovative and exciting approaches, including working with fishers and with governments.
We're encouraging broad-scale efforts at protection with our coral reef resilience work, and also at fine-scale restoration with our shellfish restoration work.
What's the most important finding from this study? What can we, as consumers and recreational users of the world's oceans, do to help prevent further degradation of the oceans?
I would love to see every one of us develop a greater sense of ownership of the oceans. With that comes stewardship.
The oceans aren't the private domain of remote industrial fishing vessels, or of oil and gas companies. We need to start placing the demands on our leaders to call for better management of our oceans.
That can sound like a call to restrict activities, but in fact it's quite the opposite — if the oceans are well-managed, they can provide more for us, and for our children.
There are personal things one can do as well. For instance, try to buy fish you know has been sustainably harvested. And if you ever find yourself headed for a beach holiday try to aim for a hotel that promotes the natural environment and encourages conservation.
Mark Spalding is a senior marine scientist at The Nature Conservancy, where he leads work to analyze global marine biodiversity, conditions and threats. He has published a number of influential books, reports and papers, particularly relating to tropical coastal environments such as coral reefs, mangroves and seagrasses.