AMC’s “The Walking Dead” is at the top of the cultural zeitgeist these days, one of the most popular television series on the air. In the show, a virus has ravaged the Earth, killing most of humanity, with the dead corpses rising to terrorize the few remaining living souls. While enormously entertaining, it is not a likely scenario for the end of the human race. Dick Cheney notwithstanding, zombies aren’t real. The end of humanity, however, could be. While it is difficult to envision a world without “us,” there are multiple scenarios staring at us, right here, right now, not far-fetched, that could wipe out all or most of humanity, leaving a wasteland for Mother Nature to reclaim. Here are some of the possible ways the reign of man- and womankind might end, no zombies needed.
Photo credit: Shutterstock
1. Global Climate Change
Climate change is the Big Kahuna of all scenarios in which our presence on Earth is ended. Despite what the climate change deniers would have you believe, climate change is real. It is being caused by human beings, with a little help from lots of farting cows emitting methane, plus that giant well of methane lurking under the Arctic ice. As we burn carbon and increase our meat-eating ways, more and more greenhouse gases are building up in the atmosphere. It is pretty easy to see the end game of this scenario. Grab a telescope and look at Venus, a planet with a thick, heat-trapping atmosphere and a surface temperature high enough to, well, melt lead. A few decades ago, climate scientist James Hanson studied Venus, and saw some parallels with what was happening on Earth. What he saw alarmed him, and he testified in Congress in 1988, warning our government that unless we changed our carbon-burning ways, we were on a course for disaster. Hanson got through to a single senator: Al Gore.
Meanwhile, the carbon keeps burning, the CO2 keeps rising, resulting in a slowly rising average Earth temperature despite the occasional freezing cold winter. On average, Earth’s temperature has been rising steadily since the Industrial Revolution unleashed our carbon-burning frenzy, resulting in a slow-moving train wreck. The hottest years in recorded history have occurred in the last decade. Author and environmental activist Bill McKibben outlines the situation:
“The Arctic ice cap is melting [releasing more greenhouse gases], the great glacier above Greenland is thinning, both with disconcerting and unexpected speed. The oceans are distinctly more acid and their level is rising…The greatest storms on our planet, hurricanes and cyclones, have become more powerful… The great rain forest of the Amazon is drying on its margins… The great boreal forest of North America is dying in a matter of years… [This] new planet looks more or less like our own but clearly isn’t."
Many environmentalists think we have already passed the point of no return. Once we pass a certain threshold, Earth will continue warming even if we do manage to cut our CO2 emissions. What we do know is that, if we don’t begin reducing the amount of CO2 we are releasing into the air, and at least minimize the damage, a planet-wide disaster is assured.
2. Loss of Biodiversity
If we don’t melt ourselves into extinction, another possible route to end times is partly a byproduct of climate change: loss of biodiversity. Human activity is responsible for massive extinctions of countless species on Planet Earth. Environment News Service reported as far back as 1999 that, “the current extinction rate is now approaching 1,000 times the background rate [what would be considered the normal rate of extinction] and may climb to 10,000 times the background rate during the next century, if present trends continue [resulting in] a loss that would easily equal those of past extinctions.”
The Millennium Ecosystem Assessment, a major environmental report released in 2005, reported 10-30 percent of mammals, birds and amphibians on the planet are in danger of extinction due to human activity, which includes deforestation (resulting in habitat destruction), CO2 emissions (resulting in acid rain), over-exploitation (such as overfishing the oceans), and invasive species introduction (like boa constrictors in the Florida Everglades). “This rapid extinction is therefore likely to precipitate collapses of ecosystems at a global scale,” said Jann Suurkula, chairman of Physicians and Scientists for Responsible Application of Science and Technology. “This is predicted to create large-scale agricultural problems, threatening food supplies to hundreds of millions of people. This ecological prediction does not take into consideration the effects of global warming which will further aggravate the situation.”
Amphibians, such as frogs and salamanders, are considered “marker species," meaning they provide important clues to the health of the ecosystem. Right now, the frog population, as well as other amphibians, has been declining rapidly. In any ecosystem, when one species dies, it affects other species, which depended on the now-extinct species for food and perhaps other necessities. When there is a sudden mass extinction of many species, a chain reaction can cause catastrophic results. There have been five mass extinctions in the history of the Earth, and many scientists are saying we are in the midst of the sixth. "We are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure,” states the International Programme on the State of the Ocean (IPSO), in the biannual State of the Oceans Report. The next mass extinction may have already begun." What would that be like? Well, in the worst one, 250 million years ago, 96 percent of ocean life and 70 percent of land life perished. What can we expect from mass extinction number six? We probably would prefer not to find out.
3. Bee Decline
Bees are dying—a lot of them, due to CCD, Colony Collapse Disorder. “One of every three bites of food eaten worldwide depends on pollinators, especially bees, for a successful harvest,” says Elizabeth Grossman, author of Chasing Molecules: Poisonous Products, Human Health. Plants depend on spreading their pollen to produce food. Bees are pollinators. No bees, no food (or at least much less). As many as 50 percent of the hives in the U.S. and Europe have collapsed in the past 10 years. The suspect in bee deaths is a class of chemicals called neonicotinoids, pesticides used on a massive scale in commercial farming. It is believed the chemicals impair the bees’ sense of direction, preventing them from returning to the hive.
With reduced pollen in the hive, fewer queen bees are produced, and eventually the colonies collapse. The European Commission has imposed a ban on these pesticides after the European Food Safety Agency concluded that they posed a “high acute risk” to honeybees. The United States, however, has declined to join Europe in banning neonicotinoids, citing other possible causes of CCD, including parasites. Meanwhile, as Nero fiddles, Rome is burning and bees are quickly disappearing. It is not hard to imagine a scenario where resulting acute food shortages bring on mass starvation, war and human extinction.
4. Bat Decline
Bees aren’t the only pollinators dying off. Bats, too, are dropping like flies. As a result of deforestation, habitat destruction and hunting, combined with a fatal fungal disease spreading among the bat population called White Nose Syndrome, bats are disappearing at an alarming rate. Besides contributing to the pollination crisis, the dwindling bat population brings about another possible human extinction scenario. As their habitats are destroyed, bats are increasingly crossing paths with the human population, in search of food and shelter. With bats come bat viruses. "It's very easy to see how pathogens can jump from animals to humans," says Jon Epstein, at the EcoHealth Alliance, a nonprofit agency dedicated to conservation and biodiversity. Every year, on average, five new infectious diseases pop up, and about 75 percent of these new diseases come from animals. It is already suspected that human killers like Ebola emerged from the bat population. Might some new human-killing pathogen mutate from bats to humans and decimate mankind?
Which leads us to a related extinction scenario: a worldwide pandemic. New diseases emerge every year. Some have the potential to devastate the population. In 1918, a strain of influenza spread worldwide and killed between 20 and 50 million people—more than were killed in all of World War I. In the past several years, diseases like SARS have come close to igniting into worldwide pandemics, and it is not at all inconceivable that, in our airplane-riding, interconnected world, some other virus could arrive on the scene with the virulence and transmissibility to decimate, if not destroy, the human population. “It is not in the interests of a virus to kill all of its hosts, so a virus is unlikely to wipe out the human race,” says Maria Zambon, a virologist with the Health Protection Agency Influenza Laboratory. “But it could cause a serious setback for a number of years. We can never be completely prepared for what nature will do: nature is the ultimate bioterrorist."
6. Biological / Nuclear Terrorism
In the interim, there are plenty of down-and-dirty, run-of-the-mill terrorists and the grand prize they all hope to get their hands on is a weapon of mass destruction like a nuclear bomb or a vial of smallpox virus. “Today's society is more vulnerable to terrorism because it is easier for a malevolent group to get hold of the necessary materials, technology and expertise to make weapons of mass destruction,” says Paul Wilkinson, chairman of the advisory board for the Center for the Study of Terrorism and Political Violence at the University of St. Andrew. “The most likely cause of large scale, mass-casualty terrorism right now is from a chemical or biological weapon.The large-scale release of something like anthrax, the smallpox virus, or the plague, would have a huge effect, and modern communications would quickly make it become a trans-national problem. There is a very high probability that a major attack will occur somewhere in the world, within our lifetimes.”
As for the nuclear threat, with increasing numbers of unstable countries like Pakistan and North Korea in possession of atomic weapons, the availability to terrorists seems only a matter of when and not if.
There are volcanoes, and then there are super-volcanoes. "Approximately every 50,000 years the Earth experiences a super-volcano. More than 1,000 square kilometers of land can be obliterated by pyroclastic ash flows, the surrounding continent is coated in ash and sulphur gases are injected into the atmosphere, making a thin veil of sulphuric acid all around the globe and reflecting back sunlight for years to come. Daytime becomes no brighter than a moonlit night.”
This lovely scenario is brought to us by Bill McGuire, director of the Benfield Hazard Research Center at University College London. About 74,000 years ago, the most powerful super-volcano eruption in human history occurred in Indonesia. It was close to the equator, and thus gases quickly passed into both hemispheres. Sunlight was blocked, and temperatures on Earth dropped worldwide for the next five to six years, below freezing even in the tropical regions. A super-volcano eruption is 12 times more likely than an asteroid hitting the Earth. Known super-volcanoes exist in Yellowstone National Park in the U.S. and Toba in Sumatra, Indonesia. And then there are the unknown ones…
8. Asteroid Impact
Recent films like Deep Impact and Armageddon have dramatized this human extinction scenario, an asteroid hitting the Earth. Hollywood is Hollywood, but in 2013, a real-life asteroid appeared without warning in Chelyabinsk, Russia. About 20 meters wide, it hurled into the Earth’s atmosphere at more than 40,000 miles per hour. Only the angle it came in at and its relatively small size prevented damage and destruction on a massive scale. But what would happen if a not-at-all uncommon mile-wide asteroid hit the Earth at this speed? Quite probably it would wipe out the human race. The tremendous explosion it would cause upon impact would fling so much dust into the atmosphere that the sun would be completely blocked off, plant life and crops would die, severe acid rain would kill ocean life, and fiery debris would cause firestorms worldwide.
This has already happened at least once. The likely reason you don’t see any dinosaurs around the neighborhood is that they were wiped out by just such an incident. Donald Yeomans of NASA: “We expect an event of this type every million years on average.”
9. Rise of the Machine
We look to Hollywood again to dramatize our next scenario. The Terminator movies entertained us with killer androids from a future where war was being waged on man by super-intelligent machines. OK, we are not there yet, but as we program more and more intelligence into our computers, exponentially increasing their capabilities every year, it is only a matter of time before they are smarter than we are. Already we entrust computers to run our stock markets, land our planes, correct our spelling, Google our trivia, and calculate our restaurant tips. In development are robots that look like us, talk like us and recognize our facial movements. How long before they are us, as we download our thoughts and memories into our hard drives, the so-called “singularity?" How long before these machines are self-aware?
Futurist and author Ray Kurzwell believes computers will be as smart as us by 2029, and by 2045 will be billions of times smarter than us. What then? Will they decide we are superfluous? Or maybe we ourselves will decide. Sounds far-fetched, I know, but some very smart people buy into this scenario; people like genius physicist Stephen Hawking: “The danger is real that they [super-computers] could develop intelligence and take over the world.”
10. Zombie Apocalypse
I know. I said zombies aren’t real. But there is a parasite called toxoplasmosa gondii. This terrifying little bug infects rats, but it can only reproduce inside the intestines of a cat, so it evolved a nifty little trick wherein it actually takes over the rat’s brain and compels it to hang out around cats. Naturally, the cat eats the rat. The cat is happy. The parasite is happy because it gets to reproduce in the cat’s intestines. The rat? Not so happy, one would suppose. Why should we care about unhappy rats? Because rats and humans are actually very similar, which is why we conduct so many medical experiments on rats. And humans are infected with the toxoplasmosa gondii parasite. About half the population of the Earth, in fact. Now it so happens that toxoplasmosa gondii does not affect humans the way it does rats. But what if it did? Viruses mutate. Viruses are manipulated in bio-weapons laboratories. Suddenly half the population would have no instinct for self-preservation. Half the population unable to think in a rational manner. Half the population suddenly very much resembling zombies. Nah. Couldn’t happen. Could it?
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On Thursday, April 22, the world will celebrate Earth Day, the largest non-religious holiday on the globe.
This Earth Day falls at a critical turning point. It is the second Earth Day since the start of the coronavirus pandemic and follows a year of devastating climate disasters, such as the wildfires that scorched California and the hurricanes that battered Central America. But the day's organizers still have hope, and they have chosen a theme to match.
"At the heart of Earth Day's 2021 theme, Restore Our Earth, is optimism, a critically needed sentiment in a world ravaged by both climate change and the pandemic," EarthDay.org president Kathleen Rogers told USA TODAY.
Last Earth Day marked the first time that the holiday was celebrated digitally to prevent the spread of COVID-19. This will largely be the case this year as well.
"Most of our Earth Day events will be virtual with the exception of individual and small group cleanups through our 'Great Global Cleanup' program," EarthDay.org's Olivia Altman told USA TODAY.
Tuesday, April 20: A Global Youth Summit begins at 2:30 p.m. ET featuring young climate activists like Greta Thunberg and Alexandria Villaseñor. This will be followed at 7 p.m. ET by "We Shall Breathe," a virtual summit organized by the Hip Hop Caucus to look at issues like the climate crisis, pollution and the pandemic through an environmental justice lens.
Wednesday, April 22: Beginning at 7 a.m. ET, Education International will lead the "Teach for the Planet: Global Education Summit." Talks will be offered in multiple languages and across multiple time zones to emphasize the importance of education in fighting the climate crisis.
Thursday, April 22: On the day itself, EarthDay.org will host its second ever Earth Day Live digital event beginning at 12 p.m. ET. This event will feature discussions, performances and workshops focusing on the day's theme of restoring our Earth through natural solutions, technological innovations and new ideas.
"EARTHDAY.ORG looks forward to contributing to the success of this historic climate summit and making active progress to Restore Our Earth," Rogers said in a press release. "We must see every country rapidly raise their ambition across all climate issues — and that must include climate education which would lead to a green jobs-ready workforce, a green consumer movement, and an educated and civically engaged citizenry around the world."
EarthDay.org grew out of the first Earth Day in 1970, which drew 20 million U.S. residents to call for greater environmental protections. The movement has been credited with helping to establish the U.S. Environmental Protection Agency and to pass landmark environmental legislation like the Clean Air and Water Acts. It has since gone on to be a banner day for environmental action, such as the signing of the Paris agreement in 2016. More than one billion people in more than 192 countries celebrate Earth Day each year.
This legacy continues. The organization called the scheduling of Biden's summit a "clear acknowledgement of the power of Earth Day."
"This is a critical stepping stone for the U.S. to rejoin the world in combating the climate crisis. In concert with several planned parallel EARTHDAY.ORG events worldwide, Earth Day 2021 will accelerate global action on climate change," EarthDay.org wrote.
Super-emitters are individual sources such as leaking pipelines, landfills or dairy farms that produce a disproportionate amount of planet-warming emissions, especially methane and carbon dioxide. Carbon Mapper, the non-profit leading the effort, hopes to provide a more targeted guide to reducing emissions by launching special satellites that hunt for sources of climate pollution.
"What we've learned is that decision support systems that focus just at the level of nation states, or countries, are necessary but not sufficient. We really need to get down to the scale of individual facilities, and even individual pieces of equipment, if we're going to have an impact across civil society," Riley Duren, Carbon Mapper CEO and University of Arizona researcher, told BBC News. "Super-emitters are often intermittent but they are also disproportionately responsible for the total emissions. That suggests low-hanging fruit, because if you can identify and fix them you can get a big bang for your buck."
The new project, announced Thursday, is a partnership between multiple entities, including Carbon Mapper, the state of California, NASA's Jet Propulsion Laboratory (JPL) and Planet, a company that designs, builds and launches satellites, according to a press release. The project is being implemented in three stages.
The initial stage, which is already complete, involved the initial engineering development. NASA and Planet will work together in the second stage to build two satellites for a 2023 launch. The third phase will launch an entire constellation of satellites starting in 2025.
The satellites will include an imaging spectrometer built by NASA's JPL, NASA explained in a press release. This is a device that can break down visible light into hundreds of colors, providing a unique signature for chemicals such as methane and carbon dioxide. Most imaging spectrometers currently in orbit have larger pixel sizes, making it difficult to locate emission sources that are not always visible from the ground. However, Carbon Mapper spectrometers will have pixels of around 98 square feet, facilitating more detailed pin-pointing.
"This technology enables researchers to identify, study and quantify the strong gas emission sources," JPL Scientist Charles Miller said in the press release.
Once the data is collected, Carbon Mapper will make it available to industry and government actors via an open data portal to help repair leaks.
"These home-grown satellites are a game-changer," California Governor Gavin Newsom said of the project. "They provide California with a powerful, state-of-the-art tool to help us slash emissions of the super-pollutant methane — within our own borders and around the world. That's exactly the kind of dynamic, forward-thinking solution we need now to address the existential crisis of climate change."
By Jenna McGuire
Commonly used herbicides across the U.S. contain highly toxic undisclosed "inert" ingredients that are lethal to bumblebees, according to a new study published Friday in the Journal of Applied Ecology.
The study reviewed several herbicide products and found that most contained glyphosate, an ingredient best recognized from Roundup products and the most widely used herbicide in the U.S. and worldwide.
While the devastating impacts of glyphosate on bee populations are more broadly recognized, the toxicity levels of inert ingredients are less understood because they are not subjected to the same mandatory testing by the U.S. Environmental Protection Agency (EPA).
"Pesticides are manufactured and sold as formulations that contain a mixture of compounds, including one or more active ingredients and, potentially, many inert ingredients," explained the Center for Food Safety in a statement. "The inert ingredients are added to pesticides to aid in mixing and to enhance the products' ability to stick to plant leaves, among other purposes."
The study found that these inert substances can be highly toxic and even block bees' breathing capacity, essentially causing them to drown. While researchers found that some of the combinations of inert ingredients had no negative impacts on the bees, one of the herbicide formulations killed 96% of the bees within 24 hours.
According to the abstract of the study:
Bees exhibited 94% mortality with Roundup® Ready‐To‐Use® and 30% mortality with Roundup® ProActive®, over 24 hr. Weedol® did not cause significant mortality, demonstrating that the active ingredient, glyphosate, is not the cause of the mortality. The 96% mortality caused by Roundup® No Glyphosate supports this conclusion.
"This important new study exposes a fatal flaw in how pesticide products are regulated here in the U.S.," said Jess Tyler, a staff scientist at the Center for Biological Diversity. "Now the question is, will the Biden administration fix this problem, or will it allow the EPA to continue its past practice of ignoring the real-world harms of pesticides?"
According to the Center for Food Safety, there are currently 1,102 registered formulations that contain the active ingredient glyphosate, each with a proprietary mixture of inert ingredients. In 2017, the group filed a legal petition calling for the EPA to force companies to provide safety data on pesticide formulations that include inert ingredients.
"The EPA must begin requiring tests of every pesticide formulation for bee toxicity, divulge the identity of 'secret' formulation additives so scientists can study them, and prohibit application of Roundup herbicides to flowering plants when bees might be present and killed," said Bill Freese, science director at the Center for Food Safety. "Our legal petition gave the EPA a blueprint for acting on this issue of whole formulations. Now they need to take that blueprint and turn it into action, before it's too late for pollinators."
ATTN @EPA: Undisclosed "inert" ingredients in #pesticide products warrant further scrutiny! ➡️ A new study compared… https://t.co/bdFwXCVHsD— Center 4 Food Safety (@Center 4 Food Safety)1618592343.0
Roundup — also linked to cancer in humans — was originally produced by agrochemical giant Monsanto, which was acquired by the German pharmaceutical and biotech company Bayer in 2018.
The merger of the two companies was condemned by environmentalists and food safety groups who warned it would cultivate the greatest purveyor of genetically modified seeds and toxic pesticides in the world.
Reposted with permission from Common Dreams.
By Ayesha Tandon
New research shows that lake "stratification periods" – a seasonal separation of water into layers – will last longer in a warmer climate.
These longer periods of stratification could have "far-reaching implications" for lake ecosystems, the paper says, and can drive toxic algal blooms, fish die-offs and increased methane emissions.
The study, published in Nature Communications, finds that the average seasonal lake stratification period in the northern hemisphere could last almost two weeks longer by the end of the century, even under a low emission scenario. It finds that stratification could last over a month longer if emissions are extremely high.
If stratification periods continue to lengthen, "we can expect catastrophic changes to some lake ecosystems, which may have irreversible impacts on ecological communities," the lead author of the study tells Carbon Brief.
The study also finds that larger lakes will see more notable changes. For example, the North American Great Lakes, which house "irreplaceable biodiversity" and represent some of the world's largest freshwater ecosystems, are already experiencing "rapid changes" in their stratification periods, according to the study.
As temperatures rise in the spring, many lakes begin the process of "stratification." Warm air heats the surface of the lake, heating the top layer of water, which separates out from the cooler layers of water beneath.
The stratified layers do not mix easily and the greater the temperature difference between the layers, the less mixing there is. Lakes generally stratify between spring and autumn, when hot weather maintains the temperature gradient between warm surface water and colder water deeper down.
Dr Richard Woolway from the European Space Agency is the lead author of the paper, which finds that climate change is driving stratification to begin earlier and end later. He tells Carbon Brief that the impacts of stratification are "widespread and extensive," and that longer periods of stratification could have "irreversible impacts" on ecosystems.
For example, Dr Dominic Vachon – a postdoctoral fellow from the Climate Impacts Research Centre at Umea University, who was not involved in the study – explains that stratification can create a "physical barrier" that makes it harder for dissolved gases and particles to move between the layers of water.
This can prevent the oxygen from the surface of the water from sinking deeper into the lake and can lead to "deoxygenation" in the depths of the water, where oxygen levels are lower and respiration becomes more difficult.
Oxygen depletion can have "fatal consequences for living organisms," according to Dr Bertram Boehrer, a researcher at the Helmholtz Centre for Environmental Research, who was not involved in the study.
Lead author Woolway tells Carbon Brief that the decrease in oxygen levels at deeper depths traps fish in the warmer surface waters:
"Fish often migrate to deeper waters during the summer to escape warmer conditions at the surface – for example during a lake heatwave. A decrease in oxygen at depth will mean that fish will have no thermal refuge, as they often can't survive when oxygen concentrations are too low."
This can be very harmful for lake life and can even increase "fish die-off events" the study notes.
However, the impacts of stratification are not limited to fish. The study notes that a shift to earlier stratification in spring can also encourage communities of phytoplankton – a type of algae – to grow sooner, and can put them out of sync with the species that rely on them for food. This is called a "trophic mismatch."
Prof Catherine O'Reilly, a professor of geography, geology and the environment at Illinois State University, who was not involved in the study, adds that longer stratified periods could also "increase the likelihood of harmful algae blooms."
The impact of climate change on lakes also extends beyond ecosystems. Low oxygen levels in lakes can enhance the production of methane, which is "produced in and emitted from lakes at globally significant rates," according to the study.
Woolway explains that higher levels of warming could therefore create a positive climate feedback in lakes, where rising temperatures mean larger planet-warming emissions:
"Low oxygen levels at depth also promotes methane production in lake sediments, which can then be released to the surface either via bubbles or by diffusion, resulting in a positive feedback to climate change."
Onset and Breakup
In the study, the authors determine historical changes in lake stratification periods using long-term observational data from some of the "best-monitored lakes in the world" and daily simulations from a collection of lake models.
They also run simulations of future changes in lake stratification period under three different emission scenarios, to determine how the process could change in the future. The study focuses on lakes in the northern hemisphere.
The figure below shows the average change in lake stratification days between 1900 and 2099, compared to the 1970-1999 average. The plot shows historical measurements (black), and the low emission RCP2.6 (blue), mid emissions RCP6.0 (yellow) and extremely high emissions RCP8.5 (red) scenarios.
Change in lake stratification duration compared to the 1970-1999 average, for historical measurements (black), the low emission RCP2.6 (blue) moderate emissions RCP6.0 (yellow) and extremely high emissions RCP8.5 (red). Credit: Woolway et al (2021).
The plot shows that the average lake stratification period has already lengthened. However, the study adds that some lakes are seeing more significant impacts than others.
For example, Blelham Tarn – the most well-monitored lake in the English Lake District – is now stratifying 24 days earlier and maintaining its stratification for an extra 18 days compared to its 1963-1972 averages, the study finds. Woolway tells Carbon Brief that as a result, the lake is already showing signs of oxygen depletion.
Climate change is increasing average stratification duration in lakes, the findings show, by moving the onset of stratification earlier and pushing the stratification "breakup" later. The table below shows projected changes in the onset, breakup and overall length of lake stratification under different emission scenarios, compared to a 1970-1999 baseline.
The table shows that even under the low emission scenario, the lake stratification period is expected to be 13 days longer by the end of the century. However, in the extremely high emissions scenario, it could be 33 days longer.
The table also shows that stratification onset has changed more significantly than stratification breakup. The reasons why are revealed by looking at the drivers of stratification more closely.
Warmer Weather and Weaker Winds
The timing of stratification onset and breakup in lakes is driven by two main factors – temperature and wind speed.
The impact of temperature on lake stratification is based on the fact that warm water is less dense than cool water, Woolway tells Carbon Brief:
"Warming of the water's surface by increasing air temperature causes the density of water to decrease and likewise results in distinct thermal layers within a lake to form – cooler, denser water settles to the bottom of the lake, while warmer, lighter water forms a layer on top."
This means that, as climate change causes temperatures to rise, lakes will begin to stratify earlier and remain stratified for longer. Lakes in higher altitudes are also likely to see greater changes in stratification, Woolway tells Carbon Brief, because "the prolonging of summer is very apparent in high latitude regions."
The figure below shows the expected increase in stratification duration from lakes in the northern hemisphere under the low (left), mid (center), and high (right) emission scenarios. Deeper colors indicate a larger increase in stratification period.
Expected increase in stratification duration in lakes in the northern hemisphere under the low (left), mid (centre) and high (right) emissions scenarios. Credit: Woolway et al (2021).
The figure shows that the expected impact of climate change on stratification duration becomes more pronounced at more northerly high latitudes.
The second factor is wind speed, Woolway explains:
"Wind speed also affects the timing of stratification onset and breakdown, with stronger winds acting to mix the water column, thus acting against the stratifying effect of increasing air temperature."
According to the study, wind speed is expected to decrease slightly as the planet warms. The authors note that the expected changes in near-surface wind speed are "relatively minor" compared to the likely temperature increase, but they add that it may still cause "substantial" changes in stratification.
The study finds that air temperature is the most important factor behind when a lake will begin to stratify. However, when looking at stratification breakup, it finds that wind speed is a more important driver.
Meanwhile, Vachon says that wind speeds also have implications for methane emissions from lakes. He notes that stratification prevents the methane produced on the bottom of the lake from rising and that, when the stratification period ends, methane is allowed to rise to the surface. However, according to Vachon, the speed of stratification breakup will affect how much methane is released into the atmosphere:
"My work has suggested that the amount of accumulated methane in bottom waters that will be finally emitted is related to how quickly the stratification break-up occurs. For example, a slow and progressive stratification break-up will most likely allow water oxygenation and allow the bacteria to oxidise methane into carbon dioxide. However, a stratification break-up that occurs rapidly – for example after storm events with high wind speed – will allow the accumulated methane to be emitted to the atmosphere more efficiently."
Finally, the study finds that large lakes take longer to stratify in spring and typically remain stratified for longer in the autumn – due to their higher volume of water. For example, the authors highlight the North American Great Lakes, which house "irreplaceable biodiversity" and represent some of the world's largest freshwater ecosystems.
These lakes have been stratifying 3.5 days earlier every decade since 1980, the authors find, and their stratification onset can vary by up to 48 days between some extreme years.
O'Reilly tells Carbon Brief that "it's clear that these changes will be moving lakes into uncharted territory" and adds that the paper "provides a framework for thinking about how much lakes will change under future climate scenarios."
Reposted with permission from Carbon Brief.
By Robert Glennon
Interstate water disputes are as American as apple pie. States often think a neighboring state is using more than its fair share from a river, lake or aquifer that crosses borders.
Currently the U.S. Supreme Court has on its docket a case between Texas, New Mexico and Colorado and another one between Mississippi and Tennessee. The court has already ruled this term on cases pitting Texas against New Mexico and Florida against Georgia.
Climate stresses are raising the stakes. Rising temperatures require farmers to use more water to grow the same amount of crops. Prolonged and severe droughts decrease available supplies. Wildfires are burning hotter and lasting longer. Fires bake the soil, reducing forests' ability to hold water, increasing evaporation from barren land and compromising water supplies.
As a longtime observer of interstate water negotiations, I see a basic problem: In some cases, more water rights exist on paper than as wet water – even before factoring in shortages caused by climate change and other stresses. In my view, states should put at least as much effort into reducing water use as they do into litigation, because there are no guaranteed winners in water lawsuits.
Alabama, pay attention to Supreme Court ruling against Florida in water war #Water #SDG6 https://t.co/wIjdoY6Ccr— Noah J. Sabich (@Noah J. Sabich)1617800452.0
Dry Times in the West
The situation is most urgent in California and the Southwest, which currently face "extreme or exceptional" drought conditions. California's reservoirs are half-empty at the end of the rainy season. The Sierra snowpack sits at 60% of normal. In March 2021, federal and state agencies that oversee California's Central Valley Project and State Water Project – regional water systems that each cover hundreds of miles – issued "remarkably bleak warnings" about cutbacks to farmers' water allocations.
The Colorado River Basin is mired in a drought that began in 2000. Experts disagree as to how long it could last. What's certain is that the "Law of the River" – the body of rules, regulations and laws governing the Colorado River – has allocated more water to the states than the river reliably provides.
The 1922 Colorado River Compact allocated 7.5 million acre-feet (one acre-foot is roughly 325,000 gallons) to California, Nevada and Arizona, and another 7.5 million acre-feet to Utah, Wyoming, Colorado and New Mexico. A treaty with Mexico secured that country 1.5 million acre-feet, for a total of 16.5 million acre-feet. However, estimates based on tree ring analysis have determined that the actual yearly flow of the river over the last 1,200 years is roughly 14.6 million acre-feet.
The inevitable train wreck has not yet happened, for two reasons. First, Lakes Mead and Powell – the two largest reservoirs on the Colorado – can hold a combined 56 million acre-feet, roughly four times the river's annual flow.
But diversions and increased evaporation due to drought are reducing water levels in the reservoirs. As of Dec. 16, 2020, both lakes were less than half full.
Second, the Upper Basin states – Utah, Wyoming, Colorado and New Mexico – have never used their full allotment. Now, however, they want to use more water. Wyoming has several new dams on the drawing board. So does Colorado, which is also planning a new diversion from the headwaters of the Colorado River to Denver and other cities on the Rocky Mountains' east slope.
Utah Stakes a Claim
The most controversial proposal comes from one of the nation's fastest-growing areas: St. George, Utah, home to approximately 90,000 residents and lots of golf courses. St. George has very high water consumption rates and very low water prices. The city is proposing to augment its water supply with a 140-mile pipeline from Lake Powell, which would carry 86,000 acre-feet per year.
Truth be told, that's not a lot of water, and it would not exceed Utah's unused allocation from the Colorado River. But the six other Colorado River Basin states have protested as though St. George were asking for their firstborn child.
In a joint letter dated Sept. 8, 2020, the other states implored the Interior Department to refrain from issuing a final environmental review of the pipeline until all seven states could "reach consensus regarding legal and operational concerns." The letter explicitly threatened a high "probability of multi-year litigation."
Utah blinked. Having earlier insisted on an expedited pipeline review, the state asked federal officials on Sept. 24, 2020 to delay a decision. But Utah has not given up: In March 2021, Gov. Spencer Cox signed a bill creating a Colorado River Authority of Utah, armed with a $9 million legal defense fund, to protect Utah's share of Colorado River water. One observer predicted "huge, huge litigation."
How huge could it be? In 1930, Arizona sued California in an epic battle that did not end until 2006. Arizona prevailed by finally securing a fixed allocation from the water apportioned to California, Nevada and Arizona.
Litigation or Conservation
Before Utah takes the precipitous step of appealing to the Supreme Court under the court's original jurisdiction over disputes between states, it might explore other solutions. Water conservation and reuse make obvious sense in St. George, where per-person water consumption is among the nation's highest.
St. George could emulate its neighbor, Las Vegas, which has paid residents up to $3 per square foot to rip out lawns and replace them with native desert landscaping. In April 2021 Las Vegas went further, asking the Nevada Legislature to outlaw ornamental grass.
The Southern Nevada Water Authority estimates that the Las Vegas metropolitan area has eight square miles of "nonfunctional turf" – grass that no one ever walks on except the person who cuts it. Removing it would reduce the region's water consumption by 15%.
Water rights litigation is fraught with uncertainty. Just ask Florida, which thought it had a strong case that Georgia's water diversions from the Apalachicola-Chattahoochee-Flint River Basin were harming its oyster fishery downstream.
That case extended over 20 years before the U.S. Supreme Court ended the final chapter in April 2021. The court used a procedural rule that places the burden on plaintiffs to provide "clear and convincing evidence." Florida failed to convince the court, and walked away with nothing.
Robert Glennon is a Regents Professor and Morris K. Udall Professor of Law & Public Policy, University of Arizona.
Disclosure statement: Robert Glennon received funding from the National Science Foundation in the 1990s and 2000s.
Reposted with permission from The Conversation.