New Study Is First to Demonstrate That Biodiversity Inoculates Against Extinction
By Jason Bittel
Biodiversity has long been touted as important for staving off extinction. The more kinds of critters you have, in other words, the less likely any one of them—or a whole bunch of them—will disappear forever.
The trouble is, no one has ever really demonstrated this idea in a lab setting. Until now.
In a study published this month in Proceedings of the National Academy of Sciences, Dirk Sanders of the University of Exeter in the United Kingdom and his coauthors show that when you remove a species from a simple community—that is, a community with fewer overall species—it can trigger extinctions in other species. What's more, the scientists provide evidence that more complex communities—those with more species—are better able to stave off the chain of events where one loss leads to another and another. Scientists refer to this phenomenon as an extinction cascade.
Why should biodiversity be a buffer against tragedy? Well, because when you lose an animal in a complex community, chances are good that something else will fill its role, said Sanders.
It's sort of impossible to control for variables in a large ecosystem like a river or a forest, so the scientists opted to study how extinction plays out in mesocosms, or miniature ecosystems. These consisted of bean and barley plants inhabited by several species of tiny insects called aphids. Aphids eat plants—technically, they suck sap—so they can represent a larger ecosystem's grazers, like deer. As for predators, the study included three parasitic wasp species, each of which preys on a specific type of aphid, as well as a fourth species of wasp that preys on any old aphid it can find.
Finally, because nature is a bit of a Russian nesting doll of horrors, there were also several species of wasps that prey on the wasps that prey on the aphids. These so-called hyperparasitoids, or parasites that prey on parasites, represent yet another level in the food chain, like jaguars that kill caimans.
Each community was set up on a table outdoors and surrounded by a 6.5-foot square of fine mesh that contained the creatures and prevented other insects from entering the mesocosm. At the same time, it allowed exposure to natural conditions like wind, rain and sunlight, just as the plants and insects would experience in the wild.
Field experiment with insect communities in mesocosms consisting of plants, aphids, and parasitoids.Dirk Sanders
To simulate extinction in half of the mesocosms, the scientists started squishing mummies. And that's when things got interesting. You see, these wasps don't prey on aphids by just killing and eating them. No, the wasps stab the aphid with a highly evolved syringe and then squirt an egg into its body. This egg hatches and begins eating the aphid alive. After the wasp larva has had its fill, it spins a cozy little cocoon around itself and begins to transform into an adult. Just like the Very Hungry Caterpillar turning into a butterfly―if that caterpillar were hanging out inside the corpse of an aphid.
The scientists sought out larvae from one parasitic wasp species, Aphidius megourae, and euthanized them with a pair of forceps. (To paraphrase T. S. Eliot, "This is the way the world ends. Not with a bang but a tweezer.")
A. megourae direct all of their destructive force against just one kind of aphid, Megoura viciae. So when this wasp was removed from the equation, its prey experienced a population explosion. After a few weeks, there were twice as many M. viciae in these mesocosms as in the control mesocosms in which no wasps were culled. That part was to be expected—get rid of wolves and mountain lions, and your deer population will go gangbusters.
What was less obvious was the way losing one species of wasp triggered the extinction of other wasp species. "This is similar to deer overpopulation," said Sanders. With so many new aphids of one species running around, the other aphid species got crowded out. And as it became harder to find those crowded-out aphids, the wasps that relied solely on them for food and a place to live began to decline until eventually they, too, went the way of the dodo.
The extinctions simulated in the lab indicated many more possible ecosystem impacts. For instance, more aphids of a certain species would likely lead to a decline of certain plants while others continue to thrive. That could affect pollinator species, the animals that eat pollinators, and so on and so on. Soil structure, microbial community, water quality—all of these variables also have the potential to change as a result of extinction cascades.
The thing is, Sanders and his colleagues found that mesocosms with more aphid and wasp species at the beginning of the experiment were less susceptible to these extinction cascades. This jibes with other studies, Sanders said, that have found that ecosystem functions, like decomposition and pollination, are dependent on maintaining a certain threshold number of species. Which makes sense—you can't expect a field full of flowers to mix genes without a ton of insects, or a carcass to disappear without the help of beetles, maggots, turkey vultures and an array of other organisms. "Therefore, in general the loss of biodiversity is a major concern, and extinction cascades can accelerate this loss," saic Sanders.
And that's a scary finding, given that scientists believe the earth is experiencing its sixth mass extinction, in which we are losing species at as much as 10,000 times the normal rate. Some species will surely be goners moving forward. However, if we can focus our conservation efforts on preserving as much biodiversity as possible, then we can give these ecosystems a chance to weather the storm.
Reposted with permission from our media associate onEarth.
- Giant Sloth Fossils, Mayan Relics Discovered in World's Largest ... ›
- Groundbreaking 'Airbnb for Butterflies' Now Open for Business ... ›
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 ... ›
- Scientists Warn Humanity in Denial of Looming 'Collapse of ... ›
EcoWatch Daily Newsletter
To save the planet, we must save the Amazon rainforest. To save the rainforest, we must save its indigenous peoples. And to do that, we must demarcate their land.
A new EarthxTV film special calls for the protection of the Amazon rainforest and the indigenous people that call it home. EarthxTV.org
- Meet the 'Women Warriors' Protecting the Amazon Forest - EcoWatch ›
- Indigenous Tribes Are Using Drones to Protect the Amazon ... ›
- Amazon Rainforest Will Collapse by 2064, New Study Predicts ... ›
- Deforestation in Amazon Skyrockets to 12-Year High Under Bolsonaro ›
- Amazon Rainforest on the Brink of Turning Into a Net Carbon Emitter ... ›
By Anke Rasper
"Today's interim report from the UNFCCC is a red alert for our planet," said UN Secretary General Antonio Guterres.
The report, released Friday, looks at the national climate efforts of 75 states that have already submitted their updated "nationally determined contributions," or NDCs. The countries included in the report are responsible for about 30% of the world's global greenhouse gas emissions.
- World Leaders Fall Short of Meeting Paris Agreement Goal - EcoWatch ›
- UN Climate Change Conference COP26 Delayed to November ... ›
- 5 Years After Paris: How Countries' Climate Policies Match up to ... ›
- Biden Win Puts World 'Within Striking Distance' of 1.5 C Paris Goal ... ›
- Biden Reaffirms Commitment to Rejoining Paris Agreement ... ›
India's New Delhi has been called the "world air pollution capital" for its high concentrations of particulate matter that make it harder for its residents to breathe and see. But one thing has puzzled scientists, according to The Guardian. Why does New Delhi see more blinding smogs than other polluted Asian cities, such as Beijing?
- This Indian Startup Turns Polluted Air Into Climate-Friendly Tiles ... ›
- How to Win the Fight Against Plastic - EcoWatch ›
In a historic move, the Delaware River Basin Commission (DRBC) voted Thursday to ban hydraulic fracking in the region. The ban was supported by all four basin states — New Jersey, Delaware, Pennsylvania and New York — putting a permanent end to hydraulic fracking for natural gas along the 13,539-square-mile basin, The Philadelphia Inquirer reported.
- Appalachian Fracking Boom Was a Jobs Bust, Finds New Report ... ›
- Long-Awaited EPA Study Says Fracking Pollutes Drinking Water ... ›
- Pennsylvania Fracking Water Contamination Much Higher Than ... ›