Early evidence shows marine conservation reduces climate change

Marine Protected Areas (MPAs) act as a safeguard for oceans, seas and estuaries. These areas contribute to the preservation of the flora and fauna that inhabit these waters, but the benefits of protected areas extend well beyond their borders. In fact, they extend beyond the water.

In a new study published in One Earth, a group of researchers explain how MPAs contribute to carbon sequestration and promote ecological and social adaptation to climate change.

Papahānaumokuākea Marine National Monument in Hawaii is the largest marine protected area in the world. (Credit: Greg McFall/NOAA)

“Marine protected areas are increasingly being touted as an ocean-based climate solution. Yet such claims remain controversial due to the diffuse and poorly synthesized literature on the climate benefits of marine protected areas,” the authors write. “To fill this knowledge gap, we conducted a systematic literature review of 22,403 publications covering 241 marine protected areas.

According to the results, carbon sequestration in MPAs increased significantly in seagrass areas, mangrove areas, and areas where sediments were not trawled. They write that “partial or complete degradation of mangroves and seagrass beds has resulted in similar decreases in sequestered carbon, indicating that even low levels of human impact result in large carbon emissions.”

They claim this is proof that “even low levels of human impact lead to large carbon emissions”.

Ecosystems and climate

The researchers found that the preserved areas were richer in biodiversity and had richer and healthier ecosystems. A higher level of food security was present in MPAs and fish stocks in the waters adjacent to these protected areas increased.

The authors also report that the benefits of these protected areas in terms of mitigation and adaptation to climate change were only obtained with high levels of protection and that these benefits increased with the duration of protection of a area. However, at present it is unclear exactly how beneficial these health benefits are for humans, but the environmental benefits are considerable.

“The health benefits are not yet clear as we don’t know if fish caught protected around MPAs are healthier or not, but more fish caught through fallout, not exported, means more fish eaten locally, and there are health benefits,” author Joachim Claudet of the National Center for Scientific Research, ZME Science said in an email.

In their study, the authors write that “(a) in the four pathways analyzed, only full and high levels of protection resulted in mitigation or adaptation benefits. In contrast, low levels of protection did not generate any benefit. Moreover, increases in species richness and income for fishers have only occurred in fully protected areas, where fishing is not permitted.

This took shape in the world’s largest marine protected area, Papahānaumokuākea Marine National Monument in Hawaii, a fully protected MPA covering more than 932,000 square miles (1.5 million square kilometers). A recent study published by the American Association for the Advancement of Science (AAAS) found many indirect benefits.

This newly published research proves that the protections provided by these regions extend beyond their borders and have a positive impact on migratory species such as bigeye tuna and yellowfin tuna. Although MPAs have been repeatedly shown to be effective in protecting local fish populations, previous research has questioned their ability to provide refuge and fishing benefits for migratory species such as tuna or the swordfish.

However, identifying potential spillovers has been a challenge.

Due to their complexity, marine ecosystems often need some time to recover before ripple effects can be observed. In addition, the creation of MPAs frequently leads to changes in human behavior, which can either mask or exaggerate fallout effects. In the AAAS study, researchers assessed whether or not the Papahānaumokuākea Marine National Monument resulted in beneficial spillovers for fishing in other areas.

Before and after the MPA’s most recent expansion in 2016, researchers assessed species-specific catch rate data for individual fishing vessels operating near and far from the protected area. Their research provided conclusive evidence that the protections afforded to two migratory species that pass through the MPA – yellowfin tuna and bigeye tuna – have resulted in spillover effects outside Papahānaumokuākea borders, which were previously only observed for resident fish populations. These effects included an increase in the overall fish population.

“The benefits of MPAs can help fishers better adapt to ecosystem changes due to climate change,” Claudet of the One Earth report said in his email. “There is no doubt that increasing levels of protection (is vital) in existing MPAs because (the) climate needs full protection.”

Teresa H. Sadler