Biodiversity levels outside Hawaii ocean reserve improve: study

What’s happening? Catches of bigeye and yellowfin tuna near a 1.5m sq km Hawaiian marine reserve have increased by 12% and 54% over a three-year period, respectively, according to researchers. The Papahanaumokuakea Marine National Monument was expanded in 2016 to create the world’s biggest fully protective no-catch ocean sanctuary for marine species.

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Why does this matter?

The study’s findings show marine protected areas (MPAs) can achieve “win-win-win” results for the environment, local communities and fishing industries. This is the first time an MPA has demonstrated protection to highly mobile, migratory species on a large scale and shows their benefits travel beyond the boundaries of MPAs to support broader ocean biodiversity, strengthening the argument for introducing more no-fishing zones – particularly across migratory routes which can benefit species including tuna, sharks and turtles.

MPAs are known to be one of the most effective measures for improving marine conservation. Approximately 6.2% of the global ocean is currently protected through MPAs, but less than half of this – just 2.4% – are fully or highly protected from fishing activity and its associated impacts, according to the Marine Protection Atlas. While it is well understood that marine protected areas offer protection to some sedentary species including lobsters or coral, the spillover benefits of MPAs to marine life in nearby areas have previously been questioned.

The Papahanaumokuakea reserve is around four times the size of California’s land mass and was expandedsix years ago. The area spans a cluster of atolls and small low-lying islands and contain a diverse range of coral reefs, submerged banks and lagoons. Hawaiian endemic species make up around 25% of the species found within the reserve. It is also a key breeding ground for the Hawaiian monk seal and a critically important nesting area for green sea turtles. Commercial fishing within the reserve is banned, while additional measures including officer patrols, surveillance flights and US coastguard vessel visits also deter illegal fishing activities.

Researchers from the University of Hawaii and the University of Wisconsin-Madison used a statistical technique known as “difference in difference” to compare catch rates of marine life from 2016 to 2019 with those recorded between 2010 to 2013 – prior to the reserve’s expansion – across the reserve’s central areas with areas located further away.

The biggest fish catch increases were located between 100 and 200 nautical miles away from the reserve’s borders. Alongside catch rate growth (the number of tuna caught per every 1,000 hooks deployed) for tuna species, catch rates for all fish species combined rose by 8%.

The researchers’ findings are a success for marine biodiversity alongside the broader fishing industry, of which tuna generates approximately $40bn in revenue each year and supports employment for millions globally. From a social perspective, yellowfin and bigeye tuna hold cultural significance for local Hawaii communities and represent a key part of their diet.

Marine reserves have delivered simultaneous positive environmental and socio-ecological impacts elsewhere. An MPA established off Mallorca’s coast, for instance, has generated a tenfold return on its investment and improved marine biodiversity, water quality, slowed coastal erosion, boosted tourism and local fishing catches.

From a climate change mitigation perspective, the establishment of MPAs can play a key role in enhancingblue carbon sinks and supporting carbon sequestration. Declaring MPAs protects important, carbon-rich marine habitats such as seagrass and salt marshes from physical disturbances such as bottom-trawling and other damaging fishing practices. Greater protection for marine life will further enable carbon sequestration, particularly from larger fish species such as sharks and tuna, which are known to be carbon stores, with each fish estimated to be 10% to 15% carbon.

However, it’s worth noting that the benefits of no-fishing zones can only be achieved if they are supported by sufficient regulations and enforcement. Governments, such as the UK government have been widely criticised by environmental groups for declaring MPAs but failing to implement the regulations necessary to ensure proper protection across the areas, describing them as “paper parks”. Earlier this year, data found over 90% of the UK’s offshore MPAs are still being bottom-trawled and dredged.

Source: The Guardian