Scientists at the University of California at Santa Barbara (UCSB) have ranked as many as 30 spots around the world where human activities are causing the most damage to coastal marine ecosystems. They announced July 9 that they recently published a study in the Journal of Conservation Letters that serves as the first analysis of all coastal areas of the world.
The top “hotspot” of human impact on marine ecosystems is the mouth of the Mississippi River, the scientists said. The remaining top 10 spots are in Asia and the Mediterranean, particularly adjacent to the Ganges and Mekong rivers. The study identified 31 sites around the world in Russia, China, India, Vietnam, Mozambique, Brazil and Europe. Damaging factors include urban runoff and other types of pollution. The scientists looked at the impact from nutrient levels from urban agriculture, organic pollutants from pesticides, chemicals from urban runoff and human populations.
Benjamin S. Halpern, one of the authors, based at the National Center for Ecological Analysis and Synthesis at UCSB, said limited resources available to address the “litany” of human affects on these areas forces identification of priority locations.
"Our results identify where it is absolutely imperative that land-based threats are addressed –– so-called hotspots of land-based impact –– and where these land-based sources of impact are minimal or can be ignored," he explained.
Conservation efforts at the ten worst sites will most likely fail, he said, if measures don't directly address human activities on land upstream. For example, a “dead zone” has developed in the Gulf of Mexico from nutrient runoff from upstream farms along the Mississippi River. The “dead zone” forms from an overgrowth of algae feeding on the nutrients and consume a majority of the oxygen in the water.
Most coastlines experience little impact from land activities; but because most of the drainage from human impact goes to very few large rivers, affected areas are relatively small in size, Halpern said. Marine conservation in those areas should look to what is going on in the ocean that harms coastal areas like fishing, shipping, invasive species and climate change, he said.
In a separate report, UCSB scientists reported in May that climate change, fishing, and commercial shipping top the list of threats to the ocean off the West Coast of the United States.