October 29, 2013
Mapping Human Impacts On Top Marine Predators
April Flowers for redOrbit.com - Your Universe Online
One of the richest ecosystems in the world, the California Current System, is driven by nutrient input from coastal upwelling and supports a great diversity of marine life. It is also heavily impacted by human activities, much like other coastal regions.
Researchers from the University of California, Santa Cruz (UCSC), reveal areas along the west coast where human impacts on marine predators such as whales, seals, seabirds and sea turtles are the heaviest.
Many of the high impact areas are within the boundaries of National Marine Sanctuaries, according to the study published in Nature Communications.
Sara Maxwell, who led the study as a graduate student in ocean sciences at UCSC and is now a postdoctoral scholar at Stanford University's Hopkins Marine Station, says this means there are good opportunities for improving management strategies.
"The sanctuaries are located close to the coast in areas where there are a lot of human activities and a lot of marine life, so it's not surprising that we see a lot of impacts there," Maxwell said. She notes that oil spills were a big concern when the sanctuaries were established, and many do not limit activities such as fishing, although they are actively engaged in managing industries such as shipping.
"With the sanctuaries already in place, we have an opportunity to increase protections. The results of this study allow us to be more specific in where we focus management efforts so that we can minimize the economic impact on people," she said.
Along the west coast, five National Marine Sanctuaries cover nearly 15,000 square miles. Protection would be expanded north to Point Arena,a key area the study identified, if a proposed expansion goes through of the Gulf of the Farallones and Cordell Bank National Marine Sanctuaries.
The health of marine ecosystems depends on marine mammals and other predators. The researchers analyzed tracking data for eight species of marine predators: blue whales, humpback whales, northern elephant seals, California sea lions, black-footed and Laysan albatrosses, sooty shearwaters, and leatherback sea turtles. These eight marine animals were drawn from the 23 species of marine predators whose movements have been tracked since 2000 as part of the Tagging of Pacific Predators (TOPP) program. Maxwell said the eight species were chosen because they are ecologically important but not commercially exploited.
The TOPP data reveals that many marine predator species travel thousands of miles every year. Even so, they often concentrate within small-scale "hotspots" to breed or feed on fish and other prey. The California Current System includes many such hotspots.
The TOPP data was combined with a database of human impacts in the California Current System that was developed by a group led by coauthor Benjamin Halpern at UC Santa Barbara. Twenty-four stressors -- fishing, shipping, climate change, etc. -- associated with human activities were analyzed for relative impact on each species. This analysis yielded maps showing the areas of greatest impact for each of the species.
"Areas where key habitats and human impacts overlap represent important areas for conservation efforts," Maxwell said. "In other cases, areas of high human activities are not key habitats for predators. As a result, we can maximize both conservation of marine predators and human uses that our coastal communities depend on."
The research team suggests that protecting key habitat without considering the impact of human activity results in missed opportunities for sustainable resource use. "Having this detailed spatial information will help us move toward a more sustainable management approach," said Elliott Hazen, a research biologist at UCSC and the NOAA Southwest Fisheries Science Center.
One of the goals of the TOPP program is providing information to support management and policy decisions, using sophisticated tags with satellite- or light-based geolocation capabilities to track the movements of top predators throughout the Pacific Ocean.
"A major component of the TOPP program was to identify important conservation areas of the North Pacific Ocean. This paper is a significant step forward in increasing our awareness of the 'blue Serengeti' that lies just off the west coast of the U.S.," said Dan Costa, one of the co-founders of TOPP.