
By Jason Bittel
Waves lap at motionless heaps of blubber and fins and the sun bears down on chapped skin. Gulls start to, well, do what gulls do. This heartbreaking scene happened in January when nearly 100 false killer whales became stranded along a remote shore in the Florida Everglades.
Authorities tried to steer the cetaceans back out to sea, but most were too exhausted or too entangled in the mangroves to make the last-ditch effort. In the end, more than 80 of the whales died. Just a few months later, a similar tragedy played out on the coast of New Zealand, this time with hundreds of pilot whales.
When a single whale beaches itself, the cause is thought to be injury, illness or old age. But when dozens or even hundreds, of the animals come ashore at once, scientists think something more is at play. While no one can say definitively what causes mass strandings, a growing body of research seems to point to one trigger.
Noise.
According to a study published last month in the Journal of Experimental Biology, noise pollution such as ship traffic and seismic testing may force marine mammals to exhaust more energy on their dives than usual. This is particularly bad news because today our oceans are noisier than ever.
The oil and gas industry searches for its next score using giant air-gun explosions beneath the surface. And when fossil fuels are found, the drills used to extract them create even more of a din. Meanwhile, the U.S. Navy sends far-reaching sonar into the sea day and night as part of routine monitoring and training exercises. Furthermore, every ship that isn't powered by wind adds to the undersea clatter with its generators, propellers and engines. Making matters worse, sound travels much farther in water than it does in air, which means each aural insult can radiate outward for miles and miles from its source.
"For whales, dolphins and other marine life, industrial and military noise is a death of a thousand cuts," said Michael Jasny, a marine mammal expert with the Natural Resources Defense Council. "It degrades their foraging, keeps them from finding potential mates, silences them and drives them from their homes. Human noise has emerged as a major environmental threat and there is virtually no corner of the ocean that is free of it."
The study's lead author, Terrie Williams, has been studying this problem for more than a dozen years as a wildlife eco-physiologist. When she started, very little was known about what was going on inside marine mammals that might be causing their mysterious, untimely deaths. That changed when wildlife veterinarian Paul Jepson published a 2003 study in Nature that found gas bubbles in the livers of stranded cetaceans. That would indicate decompression illness or the bends.
As you know, whales and dolphins breathe air at the surface and dive below for food and travel. In order to adjust between the two environments, they have what's called a diving response or reflex, which allows the body to shift its physiological priorities from what works best in air to what works best underwater. When down below, for instance, the heart rate lowers, blood vessels constrict and blood flow slows down. So for them to fall victim to decompression is definitely odd. "It seemed impossible," said Williams, "due to all of the biological safeguards that marine mammals have in place for diving without injury."
However, the bubbles in stranded whales' livers showed that the dive response doesn't always work. Williams wondered whether that diving response was less automatic than previously thought.
Through a new technology that Williams and her team invented, the researchers were able to place a device on diving dolphins to monitor second-by-second changes in heart rate, stroking mechanics and depth changes. The scientists learned that a marine mammal's diving response is related to both the depth to which it dives and the amount of exertion it takes to get there. This was really important, said Williams, because it showed that the movement of nitrogen and oxygen throughout the animal's body is not set in stone. That is, a whale or a dolphin might be able to dive safely in one scenario but not in another.
The next step was to prove that an outside factor, such as noise pollution, could possibly push the animal's physiology from its normal, safe diving state to a more rushed and risky kind of dive. This is where Williams's most recent research comes in.
Working in a deep pool aquarium, Williams and her colleagues trained retired military dolphins to wear the cetacean equivalent of Fitbits. The dolphins were taught to navigate through an underwater obstacle course at both a regular pace and a faster, escape-like pace to simulate both kinds of dives. The animals then surfaced under a sealed hood that measured the mammals' exhalations. In other words, Williams wanted to know "how much of the internal oxygen scuba tank is used during a dive by a dolphin, especially if it is trying to escape oceanic noise."
Predictably, the scientists found that it cost dolphins about twice as much physiologically to perform escape dives as opposed to dives at regular speed.
Marine mammals, of course, are not all the same. Whales are built differently from dolphins and even between whale species, body shape and dive adaptations vary. (Just think about the differences between a sperm whale and a blue whale). The scientists also had to account for the fact that larger animals require more energy to start moving but need less energy to keep all that blubber cruising once they reach higher speeds.
Fortunately, the researchers were able to make use of other studies that placed accelerometers on various whale species to measure dive times and depths. Using those data, they came up with a formula that allowed them to estimate the costs of swimming fast and slow for various types of cetaceans.
As a proof of concept, Williams and company applied their findings to the Cuvier's beaked whale, which may grow to 23 feet long and 5,500 pounds and is known for making dives of nearly two miles in depth—deeper than any other mammal. Perhaps most important, beaked whales have already been shown to be extra sensitive to noise pollution. In one 2011 study, scientists found that Blainsville's beaked whales stopped echolocating during dives when navy sonar was present and then avoided the source of the sound for two to three days. What's more, several other studies have shown a correlation between navy sonar exercises and beaked whale strandings.
So what happened when they crunched the numbers for Cuvier's beaked whales? The scientists estimated that a beaked whale may have to ratchet up its metabolic rate by more than 30 percent in order to escape oceanic noise quickly—and that's in response to a single sound event. Imagine how those energy costs might add up across repeated run-ins with acoustic pollution.
"The implications of this are enormous," said Williams. "Have the animals expended too much of their internal scuba tank? Is there enough oxygen going to their brains when they are trying to exercise at the same time that they are diving?"
These are questions Williams hopes to answer in future experiments as she attempts to establish "that last link" between ocean noise and marine mammal strandings. But with all the evidence she and other scientists have already assembled, it raises the question—how much more do we really need to know before changing our underwater ways?
Jason Bittel writes the Species Watch column for onEarth. Reposted with permission from our media associate onEarth.
‘Existential Threat to Our Survival’: See the 19 Australian Ecosystems Already Collapsing
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>- Coral Reef Tipping Point: 'Near-Annual' Bleaching May Occur ... ›
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A new EarthxTV film special calls for the protection of the Amazon rainforest and the indigenous people that call it home. EarthxTV.org
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