Researchers at the University of California Santa Barbara say a fundamental gap in understanding how humanity is affecting oceans is limiting knowledge about the pace of change in cumulative impacts on ocean ecosystem.
In their paper, “Recent pace of change in human impact on the world’s ocean,” published in Scientific Reports, combined impact humans are having on marine ecosystems.
What’s more, researchers Benjamin Halpern and Melanie Frazier said, is the need to find out the locations, drivers and patterns of these changes.
To assess the pace of change in cumulative human impacts (CHI) they calculated and mapped the cumulative impact of 14 stressors related to human activities, which included climate change, fishing and land-based pressures, on 12 marine ecosystems globally for each of 11 years spanning 2003 to 2013. The stressors included ocean acidification, sea surface temperature, sea level rise, shipping, nutrient pollution, organic pollution, direct human, light pollution, five types of commercial fishing and artisanal fishing.
Halpern and Frazer said they found that 59 percent of the ocean is experiencing significantly increasing cumulative impact, in particularly from climate change, but also from fishing, land- based pollution and shipping.
According to Frazier “increasing greenhouse gas emissions have resulted in large increases in ocean temperature which impact many ocean habitats and animals.”
High sea surface temperatures account for 75 percent of CHI, but high sea surface temperatures along coastal ecosystems only account for 40 percent of CHI, while increasing sea level explained 41 percent of the increasing CHI.
Consequences of increasing temperature are compounded by the resulting loss of sea ice and rising sea levels, Frazier said. In addition to warming, carbon dioxide emissions also cause ocean acidification, he noted. In areas with low cumulative impact, including Western Pacific oceans, increased sea surface temperatures accounted for most of the CHI increase.
One of the best actions to take would be to reduce greenhouse gas emissions, but this is challenging because it requires concerted action by many countries, and the political motivation to do so is depressingly low in many places, he said.
The study detailed that the Paris agreement would have a tremendous impact on the state of many marine ecosystems and significantly slow or halt the increasing CHI trend.
The central aim of the Paris Agreement is to strengthen global response to climate change by keeping a global temperature rise well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit temperature increase even further to 1.5 degrees Celsius.