Human impact on the oceans is growing — and climate change is the biggest culprit

(a) Absolute difference between current (as of 2013) and earlier (as of 2008) per-pixel cumulative impact scores based on 12 anthropogenic stressors that could be compared across time (max cumulative impact score for both periods=11.1). Positive scores represent an increase in cumulative impact. (b) Extreme combinations of cumulative impact and impact trend include areas with combinations of the highest (top quartile) and lowest (bottom quartile) impact and increasing (top quartile) and decreasing (bottom quartile) impact. In both panels, areas of permanent sea ice are shaded white and the area within maximum sea ice extent is shaded to indicate where scores are less certain because change in sea ice extent could not be included

 

From WashingtonPost by Chelsea Harvey

Human impact on the oceans is growing - and climate change is the biggest culprit. 

The world’s oceans have suffered a lot at the hands of humans — ask any marine conservationist. Unsustainable fishing, pollution and the effects of climate change are just a few of the issues that worry scientists and environmentalists.

While we have a good idea of which activities are causing harm to the ocean, scientists have been less clear on which ones are the most damaging and which regions of the ocean are getting the worst of it.
Now, new research has allowed scientists to map the impacts of 19 different types of human activity that have harmed the ocean over a span of five years.
The study was published Tuesday in the journal Nature Communications.

The researchers used global-scale data to map the cumulative impacts of human activities between 2008 and 2013, pinpointing which areas are under increasing stress, which areas are experiencing a decrease and which human activities are having the biggest impacts in which areas.
They found that nearly two-thirds of the ocean in experiencing an increase in these man-made impacts — and climate change is the worst of all, driving the majority of the changes the researchers observed.

 (a) Sea surface temperature anomalies, (b) nutrient input, (c) demersal destructive fishing and (d) pelagic high bycatch fishing. Positive scores represent an increase in stressor intensity. Note that colour scales differ among panels and are nonlinear.

The effects of this climate change include temperature anomalies in the water, ocean acidification and an increase in ultraviolet radiation.
These factors can create conditions unfavorable to some marine organisms, changing the composition of ecosystems, driving animals to different parts of the ocean and even causing some species to begin dying off. Ocean acidification, for instance, is notorious for interfering with the ability of certain organisms, such as coral, to build the shells they use to protect their bodies.

And while the study reveals that some types of activities, such as overfishing, tend to cluster in specific regions, the effects of climate change appear to be “truly global,” says lead author Benjamin Halpern, a professor of environmental science and management at the University of California, Berkeley.
“Any global or regional scale efforts to improve ocean condition really need to address climate change,” he says.

Within the two-thirds of the ocean experiencing an increase in stress, the researchers found that five percent of the world’s oceans are heavily harmed by human activity and likely require immediate attention.
Five percent may not sound like much, but Halpern says these areas are among the parts of the oceans most important to humans.
“Many of them are in coastal areas where a lot of people live, and so they’re places that we care about a lot and places that we don’t want to see disappear because they’re providing us so many goods and benefits from the oceans,” he says.
Some of the most highly impacted coastal regions the study identified included the Faroe Islands, the eastern Caribbean, Cape Verde and the Azore Islands.

 The relationship between current cumulative impact (as of 2013) and 5-year change in impact from 5 years before for each country’s EEZ (200 nm) is shown based on the 12 common stressors. Bubbles are scaled to the area (ln) of each country’s EEZ and colour-coded by the change in the log of coastal population (25 miles inland) per year from 2008 to 2013; a subset of countries is labelled. Grey bubbles are nearly uninhabited. Horizontal dashed red line is the global median cumulative impact score in 2013; vertical line is no change over time.

Mapping out the parts of the oceans experiencing heavy or increasing stress can help policymakers better allocate resources for conservation, targeting the areas that are in the most need.
And these maps can also help world leaders figure out the scale of the effort required to combat a problem.
For example, local efforts may be enough to target specific regions that are heavily affected by overfishing.
But combating the effects of climate change, which are widespread throughout the Earth’s oceans now, will likely require an international effort, Halpern says.

The study also identifies regions experiencing a decrease in stress from human activity.
Admittedly, these regions comprise a much smaller percentage of the world’s oceans — just 13 percent.
But pinpointing these areas can provide equally valuable information, according to Halpern.
“In some cases they do likely indicate success stories where management action has helped improve the condition of the ocean,” he says, meaning policymakers can look to these areas for information on management techniques that have proved effective.

In fact, figuring out the kinds of conservation efforts that are most effective is the most important next step for research in the field, Halpern says.
Tuesday’s study may be able to pinpoint areas that are doing well and areas that are not, but it’s not able to provide any information about the management techniques that are affecting these areas.

The study does present a fairly dire view of the health of the world’s oceans — but Halpern stresses that there are some positive takeaways, too.
“Although things are generally getting worse across the planet, there are places that are getting better,” he says.
“And hopefully we can learn from those, see what we’re doing well, and apply those lessons to other parts of the planet.”

Links :

• ClimateCentral : Climate Change Is Increasing Stress on Oceans