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To view larger map, click here. |
Earth, the blue planet, is so called because oceans and seas cover around 74 percent of its surface. However, according to the first global-scale study of human influence on marine ecosystems, these waterways may not be as blue as was previously thought.
Many researchers from different institutes got together to map the impact of human activities on all the oceans and seas of the world.
"It was a three-year effort," said Kim Selkoe, University of California Santa Barbara. "We tried to assemble all the global datasets on the different types of threats to the world's oceans and put them in the same format. That way they can all be displayed, compared and summed up into a final human impacts map."
"A series of papers have highlighted the role humans are having on the degradation of the oceans through specific activities," said Fiorenza Micheli, an associate professor of biology at Stanford. "It's timely to put it all together – to show how all the different effects sum up."
The map looked at 17 different activities such as fishing, bottom-trawling, climate change and pollution. By overlaying the impacts from all the different stressors, a composite map of human activities was produced.
Shockingly, there is not a single spot in the oceans that is unaffected by human activities. "A lot of people found it depressing," said Selkoe. "There was at least one threat occurring in every single square kilometer in the oceans from our measurements."
Another shocking result was that more than 40 percent of the water surfaces of the world were heavily impacted. These areas had "at least six or seven – and in a lot of places dozens (of stressors)," explained Selkoe.
Climate Change
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| "I think on the long term climate change is going to have the greatest impact," said Elizabeth Selig. |
The 17 stressors were chosen because they have the greatest impacts and because they had the most comprehensive sets of data.
"The major stressor is climate change. It covers the largest footprint and it's just something that every single ecosystem is going to be dealing with," said Selkoe.
The marine ecosystem most affected by climate change are coral reefs. The fragile reefs, which are home to millions of marine organisms, suffer from several diseases due to the increasing temperatures of the water.
"We were looking at how climate change is affecting coral reefs around the world and whether or not marine protected areas (MPA) or national parks in the ocean can be used to mitigate these effects," said Elizabeth Selig, a PhD student in the Ecology Curriculum at the University of North Carolina, Chapel Hill.
"We found that basically marine protected areas are beneficial but cannot protect against the effects of climate change." Selig was one of the researchers mapping the effect of the climate change stressor on the oceans. "So [MPA] are really useful for fisheries but we need other policies to reduce human activities related to climate change."
Bottom-Trawling
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| "Each individual trawler with it's nest deployed leaves a long persistent trail of sediment in it's wake, not unlike a jet trail," said John Amos. |
But while climate change factors may seem to be rather insurmountable right now, other stressors can be controlled through enforcement. One such stressor is the impact caused by bottom-trawling.
Bottom-trawling is a technique where trawlers drag huge heavy nets on the seafloor. "This essentially plows the seafloor repeatedly over large areas and it kicks up huge plumes of sediment when this trolling occurs in shallow waters," explained John Amos, founder and president of SkyTruth, an organization that specializes in using remote sensing to investigate and illustrate environmental issues, impacts and concerns.
"Each individual trawler with it's nest deployed leaves a long persistent trail of sediment in it's wake, not unlike a jet trail."
The sediment plumes can travel many kilometers with the ocean's currents before settling in another area much further from where the trawling occurred. The plumes may bury and kill thousands of marine organisms that live in the seabed.
"This raises another poorly understood and I think understudied class of impact – namely the impact caused by the sediment on the water itself. This vast quantity of mud that is being thrown up repeatedly into the water by trawler dramatically affects the physical and chemical properties of ocean waters," stressed Amos.
"Unfortunately, one of the things that happened is we always hear about trawling and it's impacts on fish and fish production. What is always missing is discussions about biodiversity," added Les Watling, professor at the University of Hawaii at Manoa, United States.
"There are a lot of other organisms in the ocean that are not fish. They live in the sediment, eat the sediment, they make houses for raising their kids – all of this is going on and all of this is destroyed always by trawling. Every time a trawler goes over the bottom it tends to remove a huge number or organisms," he said sadly.
"The impact is tremendous, it's severe, and it's very damaging. Many many organisms are removed from the seafloor by trawling. The impact is strong and big and it's incontrovertible anymore."
"The problem is vast and it's large and it needs a new management approach."
Conservative
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| "The map is a very conservative way of showing the damage being done," said Kim Selkoe. |
While the map offers a reliable measure of the damage humans cause to the oceans, it has several limitations.
"Basically we didn't account for any historical effects, so there are many things that are missing from the maps. So it's really a map of what is going on right now, not the total ecological condition of the oceans," explained Selkoe.
"So some of these blue areas are just blue because they were already trashed a long time ago. And now – looking at the last 10 or 20 years of data – they don't seem like they have changed that much."
"You might go to a beach and think 'oh well it's calm and I can see birds in the air and I saw fish swim by.' But you might not realize that a hundred years ago you would see whales with their calves in the bay and you would see sharks swim by and you would see lush sea beds in the coast and a much more complex habitat," said Selkoe passionately.
In addition to that, the researchers only used 17 different stressors. However, there are many others that were not accounted for due to the lack of global data on them.
Hope
| To hear the entire interview with Kim Selkoe, click here. |
While many researchers found the grim picture daunting, Selkoe is optimistic to a degree. "On the other side of the picture this is a great tool that will help managers improve how we use the oceans so we can minimize our impacts while maximizing the benefits we get."
While the climate change effects may be irreversible at this stage, Selkoe thinks that other stressors – such as shipping lanes that pass through breeding grounds – can be improved.
"The ships don't want to hit the whales – that's a real PR nightmare for them and they are in most cases happy to move. They just don't know where to go. So when you have these maps you can start taking an organized approach to how we manage our oceans."
"We wanted everyone in the world to be able to see this. We created an image gallery with examples of this phenomenon," said Amos. "For the 200 million or so Google Earth users around the planet we created a virtual tour as a Google Earth file that people can download."
The website of the National Center for Ecological Analysis and Synthesis also offers a file that can be added as a layer in Google Earth. "This way you can look at all the individual layers as well and see how they add up," said Selkoe.
"We want other researchers and ordinary interested citizens around the world to send us Google placemarks and images where they find visual examples that show human activities on the ocean," said Amos.
"With their help, we can build a compelling visual record that we hope will motivate citizens and governments around the world to take better care of our oceans."
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