This story is a roundup of articles from The Conversation's archives.
As cold weather settles in across North America, some communities have already started up their snowplows, while others keep watchful eyes on the forecast. Snow and ice can wreck travel plans, but they also play important ecological roles. And frozen water can take amazing forms. For days when all talk turns to winter weather, we spotlight these five stories from our archives.
1. The Strange Forms Water Can Take
Beyond snowflakes and icicles, frozen water can behave in surprising ways. For example, during very cold snaps, lakes can appear to steam like a sauna bath.
As Colorado State University atmospheric scientist Scott Denning explains, this happens because the liquid water in the lake can't be colder than the freezing point — about 32 degrees Fahrenheit. As water evaporates from the relatively warm lake into the cold dry air, it condenses from vapor (gaseous water) to tiny droplets of water in the air, which look like steam.
When it gets extremely cold, ice can form on the ocean's surface. Waves break it up, so the water starts to look like an undulating slurpee. "For anyone willing to brave the cold, it's wild to stand by the shore and watch the smoking slushy sea with its slow-motion surf," Denning writes.
2. How Road Salt Tames Ice
When a big storm is forecast, utility trucks often will head out to pre-treat streets and highways, typically spraying rock salt or saltwater solutions. But contrary to popular belief, salt doesn't melt ice.
Water freezes at 32 degrees Fahrenheit, but mixing it with salt lowers its freezing point. "The salt impedes the ability of the water molecules to form solid ice crystals," explains Julie Pollock, assistant professor of chemistry at the University of Richmond. "The degree of freezing point depression depends on how salty the solution is." When dry salt is spread on ice, it relies on the sun or the friction of car tires to melt the ice, then keeps it from re-freezing.
Pulses of salt can harm plants, water bodies and aquatic organisms when it washes off of roads — especially during spring runoff, which can carry huge doses. Researchers are working to find more benign options, and are currently studying additives including molasses and beet juice.
3. Why Trees Need Snow
Snow may seem like nothing but trouble, especially if you have to shovel it. But it's also a valuable resource. In the Northeast, environmental scientists Andrew Reinmann and Pamela Templer have found that winter snow cover acts like a blanket, protecting tree roots and soil organisms from the cold.
In experimental forest plots where Reinmann and Templer removed snow from the ground, they have observed that
"…frost penetrates a foot or more down into the soil, while it rarely extends more than two inches deep in nearby reference plots with unaltered snowpack. And just as freeze-thaw cycles create potholes in city streets, soil freezing abrades and kills tree roots and damages those that survive."
Climate change is shortening northeast winters and decreasing snowfall, with serious effects on forests. "Losing snowpack can reduce forest growth, carbon sequestration and nutrient retention, which will have important implications for climate change and air and water quality all year-round," Reinmann and Templer predict.
4. Frozen Reservoirs
Today’s #snowpack on Montgomery Pk in northern White Mtns CA, seen from down in Benton Valley. Very good snow for J… https://t.co/PrFvN50V7G— Laura Cunningham (@Laura Cunningham)1559786481.0
Snow is even more valuable in western states, where many communities get large shares of their drinking water from snowpack that lingers at high altitudes well into the warm months. Here, too, warming winters mean less snow, and scientists are already observing "snow droughts."
Adrienne Marshall a research fellow studying hydrology and climate change at the University of Idaho, defines a snow drought as a year with snowpack so low that historically it would only happen once every four years or less.
"Today, back-to-back snow droughts in the western U.S. occur around 7% of the time," she writes. "By mid-century, if greenhouse gas emissions continue to increase, our results predict that multiyear snow droughts will occur in 42% of years on average."
Snowpack is also melting earlier in the spring, which means less water is available in summer. These changes are affecting cities, farms, forests, wildlife and the outdoor recreation industry across the West year-round.
5. Can We Make It Snow?
If nature doesn't deliver as much snow as we need, what about helping it along? Many western states and agencies have tried to do just that for years by cloud-seeding — adding particles to the atmosphere that are thought to serve as artificial ice crystals, promoting the formation of snow.
There's just one hitch: No one has proved it actually works. Nonetheless, "Western states need water, and many decision-makers believe that cloud seeding can be a cost-effective way to produce it," write atmospheric scientists Jeffrey French and Sarah Tessendorf.
In a 2018 study, French, Tessendorf and colleagues used new computer modeling tools and advanced radar to see whether they could detect ice crystals forming on silver iodide particles injected into clouds. They hung imaging probes from the wings of research planes, which flew in and out of the seeded areas of clouds. Sure enough, in those zones ice crystal formation increased by hundreds, leading to the formation of snow. No such results occurred in non-seeded regions.
More research is needed to see whether cloud seeding can change water balances over large areas. And ultimately, even if that proves to be true, another question will remain: Whether it's worth the cost.
Reposted with permission from The Conversation.
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By Matt Kasson, Brian Lovett and Carolee Bull
Home gardening is having a boom year across the U.S. Whether they're growing their own food in response to pandemic shortages or just looking for a diversion, numerous aspiring gardeners have constructed their first raised beds, and seeds are flying off suppliers' shelves. Now that gardens are largely planted, much of the work for the next several months revolves around keeping them healthy.
Start With Prevention<p>Just as preventive steps like maintaining a balanced diet help keep humans healthy, home growers can take many actions to help their gardens thrive.</p><p>One key step is assessing soil fertility – the ability of soil to sustain plant growth – which can vary widely depending on your location and soil type. Low soil fertility limits food production and predisposes plants to disease and pests. University extension <a href="https://soiltesting.wvu.edu/" target="_blank">soil testing labs</a> can help evaluate the quality of garden soil and identify nutrient deficiencies and acidic soils, often at no charge.</p>
Using weed barrier landscape cloth for planting rows and mulching between rows is an effective way to suppress weeds. Matt Kasson, CC BY-ND
Diagnosing Problems<p>Common plant pathogens include <a href="https://www.apsnet.org/edcenter/disandpath/viral/introduction/Pages/PlantViruses.aspx" target="_blank">viruses</a>, <a href="https://www.apsnet.org/edcenter/disandpath/prokaryote/intro/Pages/Bacteria.aspx" target="_blank">bacteria</a>, <a href="https://www.apsnet.org/edcenter/disandpath/nematode/intro/Pages/IntroNematodes.aspx" target="_blank">nematodes</a>, <a href="https://www.apsnet.org/edcenter/disandpath/oomycete/introduction/Pages/IntroOomycetes.aspx#:%7E:text=The%20oomycetes%2C%20also%20known%20as,foliar%20blights%20and%20downy%20mildews." target="_blank">oomycetes</a> and <a href="https://www.apsnet.org/edcenter/disandpath/fungalasco/intro/Pages/IntroFungi.aspx" target="_blank">fungi</a>. All of these microorganisms, especially at an early stage of infection, are too small to see. But when they proliferate, they cause changes in plants that we can recognize.</p><p>Unlike insects, which move around on six legs or on wings through the air, pathogens can move unseen and unchecked from leaf to leaf on the wind, through the soil or in droplets of water. Some microbes have even formed intimate relationships with insects and use them as vehicles to move from plant to plant, which makes these pathogens even more challenging to manage. Unfortunately, by the time some pathogens make their presence known, the damage is already done.</p><p>We recently conducted a <a href="https://twitter.com/kasson_wvu/status/1265989041725624323" target="_blank">Twitter poll</a> of gardeners nationwide to find out which culprits plagued their gardens. People named <a href="https://ento.psu.edu/extension/factsheets/aphids" target="_blank">aphids</a>, <a href="https://ento.psu.edu/extension/factsheets/squash-vine-borer" target="_blank">squash vine borers</a>, <a href="https://ento.psu.edu/extension/factsheets/squash-bug" target="_blank">squash bugs</a> and <a href="https://ento.psu.edu/extension/factsheets/flea-beetle" target="_blank">flea beetles</a> as the most problematic insect pests. Their most troublesome pathogens included <a href="https://extension.wvu.edu/lawn-gardening-pests/plant-disease/fruit-vegetable-diseases/powdery-mildew" target="_blank">powdery mildew</a>, <a href="https://plantpath.ifas.ufl.edu/rsol/Trainingmodules/BWTomato_Module.html" target="_blank">tomato bacterial wilt</a> and <a href="https://extension.wvu.edu/lawn-gardening-pests/plant-disease/fruit-vegetable-diseases/downy-mildew" target="_blank">cucurbit downy mildew</a>.</p><p>To manage such perennial challenges, the first step is to spend time closely looking at your plants. Do you notice any insects consistently hanging around, or molds colonizing leaves or other plant parts? How about symptoms such as blight, stunting, or leaves that are yellowing, browning or wilting?</p>
This white fungal growth is an early sign of powdery mildew on a leaf of susceptible summer squash. Matt Kasson, CC BY-ND
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By Emma Charlton
The effects of climate change may more far-reaching than you think.
Hotter temperatures have been linked to a rise in energy poverty, with more people struggling to meet their energy bills from their household income, according to a new study published on ScienceDirect by researchers from Italy's Ca' Foscari University.
Value of air conditioning imports in selected OECD countries. ScienceDirect
The ‘Golden Thread’<p>The <a href="https://www.endenergypoverty.org/reports" target="_blank">Global Commission to End Energy Poverty</a> calls access to energy the "golden thread" that weaves together economic growth, human development, and environmental sustainability. And one of the <a href="https://www.weforum.org/agenda/archive/sdg-07-affordable-and-clean-energy" target="_blank">United Nations' Sustainable Development Goals</a> is to ensure access to affordable, reliable, sustainable and modern energy for all by 2030.</p><p>Sustainability also has a large role to play in the future of energy and failing to embed green policies in COVID-19 stimulus packages and underinvesting in green infrastructure are current risks, according to the <a href="http://www3.weforum.org/docs/WEF_COVID_19_Risks_Outlook_Special_Edition_Pages.pdf" target="_blank">World Economic Forum</a>.</p><p>In its vision for a 'Great Reset' – building a better world after the pandemic – the Forum and the IMF jointly backed the <a href="https://www.weforum.org/agenda/2020/06/end-fossil-fuel-subsidies-economy-imf-georgieva-great-reset-climate/" target="_blank">transition to a green economy</a> and called for an end to fossil fuel subsidies.</p>
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Scientists are urging the WHO to revisit their coronavirus guidance to focus more on airborne transmission and less on hand sanitizer and hygiene. John Lund / Photodisc / Getty Images
The World Health Organization (WHO) is holding the line on its stance that the respiratory droplets of the coronavirus fall quickly to the floor and are not infectious. Now, a group of 239 scientists is challenging that assertion, arguing that the virus is lingering in the air of indoor environments, infecting people nearby, as The New York Times reported.
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Scores of people remained stranded in southern Japan on Sunday after heavy rain the day before caused deep flooding and mudslides that left at least 34 people confirmed or presumed dead.
Care Home Inundated<p>Altogether 16 residents at an elderly care home in Kuma Village are presumed dead after the facility was flooded by water and mud.</p><p>Fifty-one other residents have been rescued by boats and taken to hospitals for treatment, officials said.</p><p>Eighteen other people elsewhere have been confirmed dead, while more than a dozen others were still missing as of Sunday afternoon.</p><p>The Fire and Disaster Management Agency said many others were still waiting to be rescued from other inundated areas.</p><p>Hitoyoshi City was also badly affected by flooding, as rains in the prefecture exceeded 100 millimeters (4 inches) per hour at their height.</p>
More Rain Forecast<p>The disaster in the Kumamoto prefecture on Kyushu island is the worst natural catastrophe since Typhoon Hagibis in October last year, which cost the lives of 90 people.</p><p>Although residents in Kumamoto prefecture were advised to evacuate their homes following the downpours on Friday evening into Saturday, many people chose not to leave for fear of contracting the coronavirus.</p><p>Officials say, however, that measures are in place at shelters to prevent the transmission of the disease.</p><p>More rain is predicted in the region, and the Japan Meteorological Agency has warned of the danger of further mudslides.</p>
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