A marine protected area (MPA) may sound like a biodiversity haven, safe from the many external stresses of human activity. What is becoming apparent, however, is that this conservation tool rarely shelters waters from warming, changing chemistry, habitat loss, or species shifts – in other words, the impacts of climate change.
Scientists are therefore increasingly recommending that MPA designs evolve from static to adaptive.
“Ten years from now, what you thought you were protecting is not there anymore because they moved [due to climate change],” says Adrian Munguia-Vega, a marine biologist at the University of Arizona. “Or the network of protected areas that you were creating to improve the resilience of these ecosystems gets completely disconnected and broken into parts.”
The need for MPAs to deliver results has grown increasingly urgent since 2022 when parties to the UN biodiversity convention agreed to conserve and manage 30% of the world’s marine and coastal areas by 2030 – known as the “30 by 30” target.
In response to this need, Munguia-Vega and 50 other scientists and conservation experts wrote “Guidelines for designing climate-smart marine protected areas”. The document, published in October 2023 in the journal One Earth, offers a framework of 21 transboundary recommendations, conceived to support marine animals and their habitats amid looming climate challenges.
China Dialogue Ocean spoke to the study’s research co-lead Nur Arafeh-Dalmau. The marine conservation scientist from Stanford University says MPAs are investments, and including climate change in their design is required to make the best of the investment. “We may not get the outcomes desired if we don’t,” he adds.
Climate adaptation in the Southern California Bight
Considering climate change in MPA designs is not a novel idea. Scientists have been discussing it for at least two decades, but the awareness has seldom translated into action. For example, the design of California’s MPA network, which is a case-study in the One Earth paper, and many in the UK, did not address climate adaptation.
What is an MPA network?
An organised group of marine protected areas. Each MPA in the network will differ in scale and degree of protection, yet all cooperate in a mutually beneficial manner. MPA networks can better reach ecological goals than an individual MPA, according to the International Union for Conservation of Nature.
Munguia-Vega says this lack of concrete measures related to climate change might be due to a lack of scientific data, and hence knowledge, to inform conservationists.
To help fill in these information gaps, a network of marine scientists including Arafeh-Dalmau and Munguia-Vega analysed the Southern California Bight during the 2010s. The bight ecoregion, stretching over 2,700 km of coastal and inland waters, lies between Point Conception in California, US, and Punta Abreojos in Baja California Sur, Mexico. The team analysed sea surface temperature data and ran models to simulate ocean dynamics according to future climate scenarios.
The bight is known for its productive waters, which support a rich ecosystem and local fishing economies. It has also been identified as a hotspot of marine climate change, perched on the front lines of rapid ocean warming, acidification and deoxygenation, as well as increasingly frequent extreme weather events like marine heatwaves and hurricanes.
Under these changes, Arafeh-Dalmau and Munguia-Vega’s study projects that both the density of larval species in the area – including of lobsters, abalones, sea urchins, California sheepheads, and sea cucumbers – and their ability to wriggle from one habitat patch to another could diminish by an average of 50% by 2100.
While drifting along the ocean current, these species will increasingly find some of their usual habitats and breeding sites decimated by extreme weather. Meanwhile, warming waters will speed up their metabolic rates and respiration, which compresses larval phases and shortens dispersal ranges. Or, in Munguia-Vega’s words: “The larvae don’t have as much time as they used to have to reach the next patch.”
These patches of habitat are individual pieces of the Southern California Bight’s overall ecosystem. Their replenishment relies on the interconnectivity that drifting larvae facilitate. As the ecological connectivity of the MPA network shrinks, each patch will become more isolated and extinction risks will increase.
“The entire [bight] system will be much less resilient and have a higher risk of population collapse,” explains Munguia-Vega. “That effectively means that you need a higher density of connected patches.”
The One Earth study suggests plans for the bight’s MPA network must be made with larval dispersal projections in mind. The network must cover a larger area and become denser and more focused on stepping-stone habitats – through which species usually pass on their dispersal journeys.
The study also advises extending the duration of MPAs to more than 25 years – if not making them permanent – and granting them a higher level of protection. Some of the MPAs are only in effect for a limited period, or even seasonally, to protect certain species and habitats, such as during spawning. Prolonging the protection could support the over-exploited species that the MPAs aim to help restore, as marine heatwaves extend the time they need to recover, the study finds.
International cooperation on border-crossing species
Larvae naturally cross international borders. Around 16% of sea urchin and sea cucumber larvae in the Southern California Bight cross between the US and Mexico, according to the One Earth paper. As for the California sheephead, a local fish species, 20% cross from Mexican waters into the US. The data suggests that supporting these ecosystems requires international collaboration.
However, Munguia-Vega says the US and Mexican governments barely communicate to ensure a smoother cross-border journey for these larvae. His paper advocates for more international cooperation in developing and managing MPA networks.
“Almost all coastal countries share the ocean with a neighbouring country, so we need to think about that,” says Arafeh-Dalmau. He believes that transboundary cooperation on MPAs can also boost international engagement, facilitating capacity-building and even enhancing peace-making efforts.
Ultimately, the solution is only to reduce emissions … This is all pointless if we don’t slow warming.John Bruno, biology professor at the University of North Carolina
Carlos Mireles, a senior environmental scientist at the California Department of Fish and Wildlife, told China Dialogue Ocean that the department agrees with the findings of the paper. In fact, a researcher from the department was a co-author, as were representatives of other state agencies.
California carried out its first comprehensive examination of its MPA management programme and broader network performance in 2022, Mireles adds. Out of that review came a recommendation for the state to incorporate climate change considerations into all aspects of the programme.
The state is formally reviewing proposals requesting changes to its MPA network, he says. “Coordination across government agencies, including our counterparts in Mexico, tribal governments, researchers in MPA and climate science, and other partners, will be central to this review process,” he adds.
China Dialogue Ocean also reached out to Mexico’s Comisión Nacional de Áreas Naturales Protegidas but had not received a response at the time of publication.
It all comes down to cutting emissions
As the overall ocean environment deteriorates, there may still be some exceptional areas where species are more insulated from the consequences, such as rocky reefs and seagrass meadows. These are known as “climate refugia” and the One Earth study recommends prioritising their protection.
The Southern California Bight’s refugia are kelp forests. “When a heatwave hits the coast, the kelps don’t die and the species that live in the kelp forests can survive the heatwave,” explains Munguia-Vega. “Those are your ideal places to establish marine protected areas.” Preserving refugia may result in a higher species survival rate than protecting more vulnerable patches.
China Dialogue Ocean spoke to John Bruno, a biology professor at the University of North Carolina who studies tropical waters and coral reefs. Unlike areas such as the Southern California Bight, warmer waters may offer less climate refugia: “We generally have no idea where the refugia are, because there are really no places in the tropics that are safe from warming.”
Bruno expresses support for clear and realistic recommendations for MPA managers to reduce climate change impacts, but he is also conscious of the bigger picture: “Ultimately, the solution is only to reduce emissions … This is all pointless if we don’t slow warming.”
Munguia-Vega also stresses the urgency of cutting emissions and says it is the hidden message behind the study. He adds that, while scientific research can guide climate change adaptation work locally, if temperatures continue to rise and marine heatwaves strike more harshly and regularly, associated ecosystems will disintegrate. Climate refugia like kelp forests will also disappear, along with the hundreds of thousands of species that rely on them, he says.
“We are going to have to reduce our CO2 emissions,” concludes Munguia-Vega. “Otherwise, these things will get so complicated that the future will not be very optimistic.”
