Marine Heat Waves Are Becoming More Common and Intense. What Can We Do to Minimize Harm?
By Jen Monnier
In the summer of 2015, Laurie Weitkamp was walking on the beach near her coastal Oregon home when she saw something strange: The water was purple. A colony of tunicates, squishy cylindrical critters that rarely come to shore, had congregated in a swarm so thick that you could scoop them out of the water with your hand. "I'd never seen anything like it," she says.
Weitkamp, a research fisheries biologist with the Northwest Fisheries Science Center in Newport, Oregon, knew that something had been afoot in the northeast part of the Pacific Ocean since the fall of 2013, which was unusually sunny, warm and calm. A mass of warm water stretched from Mexico to Alaska and lingered through 2016, disrupting marine life. Tunicates weren't the only creature affected; sea nettle jellyfish all but disappeared, while water jellyfish populations moved north to take their place, and young salmon starved to death out at sea, according to a report by Weitkamp and colleagues. Scientists dubbed this event "The Blob."
Marine heat waves like The Blob have cropped up around the globe more and more often over the past few decades. Scientists expect climate change to make them even more common and long lasting, harming vulnerable aquatic species as well as human enterprises such as fishing that revolve around ocean ecosystems. But there's no reliable way to know when one is about to hit, which means that fishers and wildlife managers are left scrambling to reduce harm in real time.
Fisheries biologist Laurie Weitkamp is helping develop policies to reduce the threat of marine heat waves, which can devastate ocean life. Photo courtesy of Laurie Weitkamp
Now, oceanographers are trying to uncover what drives these events so that people can forecast them and so minimize the ecological and economic damage they cause.
The Blob, which lasted three years, is the longest marine heat wave on record. Before that, a heat wave that began in 2015 in the Tasman Sea lasted more than eight months, killing abalone and oysters. A 2012 heat wave off the East Coast of Canada and the U.S., the largest on record at the time, pushed lobsters northward. It beat the previous record — a 2011 marine heat wave that uprooted seaweed, fish and sharks off western Australia. Before that, a 2003 heat wave in the Mediterranean Sea clinched the record while ravaging marine life.
As Earth's climate warms, record-setting marine heat waves are becoming more frequent and severe. Map adapted from Marine Heatwaves International Working Group.
Heat waves are a natural part of ocean systems, says Eric Oliver, an assistant professor of oceanography at Dalhousie University in Nova Scotia, Canada. As with temperature on land, there's an average ocean temperature on any particular day of the year: Sometimes the water will be warmer, sometimes it will be colder, and every once in a while it will be extremely warm or cold.
But greenhouse gas emissions have bumped up the average temperature. Now, temperatures that used to be considered extremely warm happen more often — and every so often, large sections of the ocean are pushed into unprecedented heat, Oliver says.
Pelagic ocean ecosystems, however, have not caught up to these hotter temperatures. Organisms may be able to survive a steady temperature rise, but a heat wave can push them over the edge.
When blue swimmer crabs started dying in western Australia's Shark Bay after the 2011 heat wave, the government shut down blue crab fishing for a year and a half. This was hard on industry at the time, says Peter Jecks, managing director of Abacus Fisheries, but it managed to save crab populations. Not all creatures were so lucky — abalone near the heat wave's epicenter still haven't recovered.
"If you don't have strong predictions [of marine heat waves], you can't be proactive. You're left to be reactive," says Thomas Wernberg, an associate professor of marine ecology at the University of Western Australia.
See Them Coming
After Wernberg saw his region's sea life devastated by the heat wave, he recruited scientists from many disciplines in 2014 to begin studying these extreme events in what became the Marine Heatwaves International Working Group. The group held their first meeting in early 2015 and has since created protocols for defining and naming marine heat waves, tracking where they happen and measuring their ecological and socioeconomic impacts.
If we could see heat waves coming, aquaculturists, fishers and wildlife managers would have a better chance at saving money and species, Wernberg says. Seafood farmers could hold off stocking their aquaculture facilities with vulnerable species. Lawmakers could enact seasonal fishing closures or temporarily expand protected areas. Scientists could store animals or seeds of vulnerable plants.
That's why scientists around the world are trying to understand what triggers extreme warming in the ocean. Oliver is one such scientist. He feeds ocean data gathered by scientists, satellites, buoys, and deep-diving robots into computer modeling software to identify the forces that drive marine heat waves.
It's a relatively new field of research for which there are still few definitive answers. But past heat waves can be broadly classified into two categories, Oliver says: those driven by the ocean and those driven by the atmosphere.
For an example of an ocean-driven heat wave, Oliver points to the 2015 Tasman Sea heat wave. An ocean current that flows south down the East Coast of Australia normally veers toward New Zealand, but in 2015 it pulsed westward toward Tasmania, bringing a wave of warm water from the tropics that lingered more than six months. "Tropical fish were seen in water that is normally almost subpolar in temperature," Oliver says.
On the other hand, a 2019 heat wave in the Pacific, the so-called "Blob 2.0," was brought down from the atmosphere, according to Dillon Amaya, a climate scientist at the University of Colorado, Boulder. Using computer models, Amaya found that this heat wave emerged when a weather system over the Pacific lost steam, leading to weaker-than-usual winds. Wind helps cool the ocean by evaporating surface water in the same way a breeze cools a person's sweaty skin. But stagnant air above the Pacific locked more of the sun's heat into the water that year.
The recent "Blob 2.0" heat wave bears some resemblance to "The Blob," which disrupted marine life from Mexico to Alaska over the course of three years. NOAA Coral Reef Watch
Amaya is able to simulate heat waves thanks to recent technological advances. Scientists have known for decades that marine heat waves exist, he says, but "we have just begun to recognize these events as unique and deterministic — something we can predict — in the last five to 10 years."
That understanding inspired researchers to build computer simulations capable of playing out complicated ocean processes by weaving together information about ocean and atmospheric currents, sea surface temperature and salinity. Creating these simulations helps them learn more about heat wave mechanics, which lays the groundwork for predicting future events.
Back in Oregon, Weitkamp is part of the group that manages the Pacific Salmon Treaty between the U.S. and Canada. As heat waves like The Blob and Blob 2.0 deplete fish populations, the group is trying to figure out how to create policies better suited to this new normal. Knowing when the next one might hit could help.
"These heat waves have been a good wake-up call," she says. "People are trying to figure out how they're going to adapt."
Reposted with permission from Ensia.
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By Dana M Bergstrom, Euan Ritchie, Lesley Hughes and Michael Depledge
In 1992, 1,700 scientists warned that human beings and the natural world were "on a collision course." Seventeen years later, scientists described planetary boundaries within which humans and other life could have a "safe space to operate." These are environmental thresholds, such as the amount of carbon dioxide in the atmosphere and changes in land use.
The Good and Bad News<p><span>Ecosystems consist of living and non-living components, and their interactions. They work like a super-complex engine: when some components are removed or stop working, knock-on consequences can lead to system failure.</span></p><p>Our study is based on measured data and observations, not modeling or predictions for the future. Encouragingly, not all ecosystems we examined have collapsed across their entire range. We still have, for instance, some intact reefs on the Great Barrier Reef, especially in deeper waters. And northern Australia has some of the most intact and least-modified stretches of savanna woodlands on Earth.</p><p><span>Still, collapses are happening, including in regions critical for growing food. This includes the </span><a href="https://www.mdba.gov.au/importance-murray-darling-basin/where-basin" target="_blank" rel="noopener noreferrer">Murray-Darling Basin</a><span>, which covers around 14% of Australia's landmass. Its rivers and other freshwater systems support more than </span><a href="https://www.abs.gov.au/ausstats/[email protected]/latestproducts/94F2007584736094CA2574A50014B1B6?opendocument" target="_blank" rel="noopener noreferrer">30% of Australia's food</a><span> production.</span></p><p><span></span><span>The effects of floods, fires, heatwaves and storms do not stop at farm gates; they're felt equally in agricultural areas and natural ecosystems. We shouldn't forget how towns ran out of </span><a href="https://www.mdba.gov.au/issues-murray-darling-basin/drought#effects" target="_blank" rel="noopener noreferrer">drinking water</a><span> during the recent drought.</span></p><p><span></span><span>Drinking water is also at risk when ecosystems collapse in our water catchments. In Victoria, for example, the degradation of giant </span><a href="https://theconversation.com/logging-must-stop-in-melbournes-biggest-water-supply-catchment-106922" target="_blank" rel="noopener noreferrer">Mountain Ash forests</a><span> greatly reduces the amount of water flowing through the Thompson catchment, threatening nearly five million people's drinking water in Melbourne.</span></p><p>This is a dire <em data-redactor-tag="em">wake-up</em> call — not just a <em data-redactor-tag="em">warning</em>. Put bluntly, current changes across the continent, and their potential outcomes, pose an existential threat to our survival, and other life we share environments with.</p><p><span>In investigating patterns of collapse, we found most ecosystems experience multiple, concurrent pressures from both global climate change and regional human impacts (such as land clearing). Pressures are often </span><a href="https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2664.13427" target="_blank" rel="noopener noreferrer">additive and extreme</a><span>.</span></p><p>Take the last 11 years in Western Australia as an example.</p><p>In the summer of 2010 and 2011, a <a href="https://theconversation.com/marine-heatwaves-are-getting-hotter-lasting-longer-and-doing-more-damage-95637" target="_blank" rel="noopener noreferrer">heatwave</a> spanning more than 300,000 square kilometers ravaged both marine and land ecosystems. The extreme heat devastated forests and woodlands, kelp forests, seagrass meadows and coral reefs. This catastrophe was followed by two cyclones.</p><p>A record-breaking, marine heatwave in late 2019 dealt a further blow. And another marine heatwave is predicted for <a href="https://www.theguardian.com/environment/2020/dec/24/wa-coastline-facing-marine-heatwave-in-early-2021-csiro-predicts" target="_blank" rel="noopener noreferrer">this April</a>.</p>
What to Do About It?<p><span>Our brains trust comprises 38 experts from 21 universities, CSIRO and the federal Department of Agriculture Water and Environment. Beyond quantifying and reporting more doom and gloom, we asked the question: what can be done?</span></p><p>We devised a simple but tractable scheme called the 3As:</p><ul><li>Awareness of what is important</li><li>Anticipation of what is coming down the line</li><li>Action to stop the pressures or deal with impacts.</li></ul><p>In our paper, we identify positive actions to help protect or restore ecosystems. Many are already happening. In some cases, ecosystems might be better left to recover by themselves, such as coral after a cyclone.</p><p>In other cases, active human intervention will be required – for example, placing artificial nesting boxes for Carnaby's black cockatoos in areas where old trees have been <a href="https://www.environment.gov.au/biodiversity/threatened/publications/factsheet-carnabys-black-cockatoo-calyptorhynchus-latirostris" target="_blank" rel="noopener noreferrer">removed</a>.</p><p><span>"Future-ready" actions are also vital. This includes reinstating </span><a href="https://www.abc.net.au/gardening/factsheets/a-burning-question-fire/12395700" target="_blank" rel="noopener noreferrer">cultural burning practices</a><span>, which have </span><a href="https://theconversation.com/australia-you-have-unfinished-business-its-time-to-let-our-fire-people-care-for-this-land-135196" target="_blank" rel="noopener noreferrer">multiple values and benefits for Aboriginal communities</a><span> and can help minimize the risk and strength of bushfires.</span></p><p>It might also include replanting banks along the Murray River with species better suited to <a href="https://www.abc.net.au/gardening/factsheets/my-garden-path---matt-hansen/12322978" target="_blank" rel="noopener noreferrer">warmer conditions</a>.</p><p>Some actions may be small and localized, but have substantial positive benefits.</p><p>For example, billions of migrating Bogong moths, the main summer food for critically endangered mountain pygmy possums, have not arrived in their typical numbers in Australian alpine regions in recent years. This was further exacerbated by the <a href="https://theconversation.com/six-million-hectares-of-threatened-species-habitat-up-in-smoke-129438" target="_blank" rel="noopener noreferrer">2019-20</a> fires. Brilliantly, <a href="https://www.zoo.org.au/" target="_blank" rel="noopener noreferrer">Zoos Victoria</a> anticipated this pressure and developed supplementary food — <a href="https://theconversation.com/looks-like-an-anzac-biscuit-tastes-like-a-protein-bar-bogong-bikkies-help-mountain-pygmy-possums-after-fire-131045" target="_blank" rel="noopener noreferrer">Bogong bikkies</a>.</p><p><span>Other more challenging, global or large-scale actions must address the </span><a href="https://www.youtube.com/watch?v=iICpI9H0GkU&t=34s" target="_blank" rel="noopener noreferrer">root cause of environmental threats</a><span>, such as </span><a href="https://www.nature.com/articles/s41559-018-0504-8" target="_blank" rel="noopener noreferrer">human population growth and per-capita consumption</a><span> of environmental resources.</span><br></p><p>We must rapidly reduce greenhouse gas emissions to net-zero, remove or suppress invasive species such as <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/mam.12080" target="_blank" rel="noopener noreferrer">feral cats</a> and <a href="https://theconversation.com/the-buffel-kerfuffle-how-one-species-quietly-destroys-native-wildlife-and-cultural-sites-in-arid-australia-149456" target="_blank" rel="noopener noreferrer">buffel grass</a>, and stop widespread <a href="https://theconversation.com/to-reduce-fire-risk-and-meet-climate-targets-over-300-scientists-call-for-stronger-land-clearing-laws-113172" target="_blank" rel="noopener noreferrer">land clearing</a> and other forms of habitat destruction.</p>
Our Lives Depend On It<p>The multiple ecosystem collapses we have documented in Australia are a harbinger for <a href="https://www.iucn.org/news/protected-areas/202102/natures-future-our-future-world-speaks" target="_blank">environments globally</a>.</p><p>The simplicity of the 3As is to show people <em>can</em> do something positive, either at the local level of a landcare group, or at the level of government departments and conservation agencies.</p><p>Our lives and those of our <a href="https://theconversation.com/children-are-our-future-and-the-planets-heres-how-you-can-teach-them-to-take-care-of-it-113759" target="_blank">children</a>, as well as our <a href="https://theconversation.com/taking-care-of-business-the-private-sector-is-waking-up-to-natures-value-153786" target="_blank" rel="noopener noreferrer">economies</a>, societies and <a href="https://theconversation.com/to-address-the-ecological-crisis-aboriginal-peoples-must-be-restored-as-custodians-of-country-108594" target="_blank" rel="noopener noreferrer">cultures</a>, depend on it.</p><p>We simply cannot afford any further delay.</p><p><em><a rel="noopener noreferrer" href="https://theconversation.com/profiles/dana-m-bergstrom-1008495" target="_blank" style="">Dana M Bergstrom</a> is a principal research scientist at the University of Wollongong. <a rel="noopener noreferrer" href="https://theconversation.com/profiles/euan-ritchie-735" target="_blank" style="">Euan Ritchie</a> is a professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences at Deakin University. <a rel="noopener noreferrer" href="https://theconversation.com/profiles/lesley-hughes-5823" target="_blank">Lesley Hughes</a> is a professor at the Department of Biological Sciences at Macquarie University. <a rel="noopener noreferrer" href="https://theconversation.com/profiles/michael-depledge-114659" target="_blank">Michael Depledge</a> is a professor and chair, Environment and Human Health, at the University of Exeter. </em></p><p><em>Disclosure statements: Dana Bergstrom works for the Australian Antarctic Division and is a Visiting Fellow at the University of Wollongong. Her research including fieldwork on Macquarie Island and in Antarctica was supported by the Australian Antarctic Division.</em></p><p><em>Euan Ritchie receives funding from the Australian Research Council, The Australia and Pacific Science Foundation, Australian Geographic, Parks Victoria, Department of Environment, Land, Water and Planning, and the Bushfire and Natural Hazards CRC. Euan Ritchie is a Director (Media Working Group) of the Ecological Society of Australia, and a member of the Australian Mammal Society.</em></p><p><em>Lesley Hughes receives funding from the Australian Research Council. She is a Councillor with the Climate Council of Australia, a member of the Wentworth Group of Concerned Scientists and a Director of WWF-Australia.</em></p><p><em>Michael Depledge does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</em></p><p><em>Reposted with permission from <a href="https://theconversation.com/existential-threat-to-our-survival-see-the-19-australian-ecosystems-already-collapsing-154077" target="_blank" style="">The Conversation</a>. </em></p>
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