The mouth of the Mississippi River, where it meets of Gulf of Mexico, is the most at-risk coastal marine ecosystem on the planet, according to a newly published study.
Scientists at the University of California, Santa Barbara recently published a study in the Journal of Conservation Letters including the first integrated analysis of all coastal areas of the world.
"Resource management and conservation in coastal waters must address a litany of impacts from human activities, from the land, such as urban runoff and other types of pollution, and from the sea," said Benjamin S. Halpern, one of the report’s main authors.
"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 said.
The hottest hotspot is at the mouth of the Mississippi River, explained Halpern, with the other top 10 in Asia and the Mediterranean. "These are areas where conservation efforts will almost certainly fail if they don’t directly address what people are doing on land upstream from these locations."
Nutrient runoff from upstream farms has caused a persistent "dead zone" in the Gulf of Mexico, where the Mississippi runs into this body of water. The dead zone is caused by an overgrowth of algae that feeds on the nutrients and takes up most of the oxygen in the water.
The authors surveyed four key land-based drivers of ecological change: nutrient input from agriculture in urban settings; organic pollutants derived from pesticides; inorganic pollutants from urban runoff; and direct impact of human populations on coastal marine habitats.
Halpern explained that a large portion of the world’s coastlines experience very little effect of what happens on land–nearly half of the coastline and more than 90% of all coastal waters. "This is because a vast majority of the planet’s landscape drains into relatively few very large rivers, that in turn affect a small amount of coastal area," said Halpern. "In these places with little impact from human activities on land, marine conservation can and needs to focus primarily on what is happening in the ocean. For example: fishing, climate change, invasive species, and commercial shipping."
The report is available as a PDF at the link below.
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