Climate Change Is Shrinking Winter Snowpack and Harming Northeast Forests Year-Round
By Andrew Reinmann and Pamela Templer
Climate change often conjures up images of heat, drought and hurricanes. But according to the latest U.S. National Climate Assessment, released on Nov. 23, 2018, winters have warmed three times faster than summers in the Northeast in recent years. These changes are also producing significant effects.
Historically, more than 50 percent of the northern hemisphere has had snow cover in winter. Now warmer temperatures are reducing the depth and duration of winter snow cover. Many people assume that winter is a dormant time for organisms in cold climates, but decades of research now shows that winter climate conditions—particularly snowpack—are important regulators of the health of forest ecosystems and organisms that live in them.
In particular, our work over the last decade shows that declining snow cover may impair tree health and reduce forests' ability to filter air and water. Our latest study finds that continued winter warming could greatly reduce snow cover across the northeastern U.S., causing large declines in tree growth and forest carbon storage.
Changes in snowmelt-related streamflow timing for rivers, 1960-2014, show that snow is melting earlier in the year in the Northeast. USGCRP / NCA4
Snow as a Blanket
We study northern hardwood forests, which are dominated by sugar maple, yellow birch and American beech trees and span 85,000 square miles, from Minnesota and south-central Canada east to the Canadian Maritime Provinces and the northeastern U.S. These forests are famed for their vibrant fall colors. They generate revenue by drawing tourists, hikers, hunters and campers, and support timber and maple syrup industries. They also provide important ecological services, such as storing carbon and maintaining water and air quality.
When winter encroaches on this region, with temperatures often dipping well below freezing, every species needs insulation to cope. Tree roots and soil organisms like insects rely on deep snowpack for protection from cold—a literal blanket of snow. Even in sub-zero temperatures, if snow is sufficiently deep, soils can remain unfrozen.
Six decades of research from the Hubbard Brook Experimental Forest in New Hampshire—one of the longest-running studies anywhere—shows that winter snowpack is declining. Research conducted by other scholars indicates that if this trend continues, it will increase the likelihood of soil freeze-thaw cycles, with harmful effects on forest health.
How Acid Rain Transformed A Forest Into A Laboratory youtu.be
Why Northern Forests Need Snow
For more than 10 years we have manipulated winter snowpack at Hubbard Brook to study the effects of projected climate change on northern hardwood forests. In early winter, we head outdoors after each snowfall to remove snow from our experimental plots. Then we analyze how losing this insulating layer affects trees and soil.
We have found that in plots where we remove snow, 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.
This root damage triggers a cascade of ecological responses. Dead roots decompose and stimulate losses of carbon dioxide from the soil. Trees take up fewer nutrients from soil, accumulate the toxic element aluminum in their leaves and produce less branch growth. Nitrogen, a key nutrient, can wash out of soils. Soil insect communities become less abundant and diverse.
Research plot at Hubbard Brook Experimental Forest with snowpack experimentally reduced Pam Templer, CC BY-ND
Declining Snowpack Affects Tree Growth
In our most recent paper, our climate and hydrological models show that the area of forests across the northeastern U.S. that receives insulating midwinter snowpack could decline by 95 percent by the year 2100. Today, 33,000 square miles of forests across northern New York and New England typically have snowpack for several months in winter. By the year 2100, this area could shrink to a patch smaller than 2,000 square miles—about one-fifth the size of Vermont.
This decline will undoubtedly harm the skiing and snowmobiling industries and expose Northeast roads to more freeze-thaw cycles. It also will significantly affect tree growth.
Historical and projected changes in spatial extent of insulating winter snowpack in the northeastern U.S. (left panels) and the distribution of sugar maple trees and forest area influenced by insulating winter snowpack (right panels)Reinmann et al., 2018, CC BY-ND
To assess the relationship between snowpack and tree growth, we used a specialized hollow drill bit called an increment borer to remove straw-sized wood cores from multiple sugar maple stems. Each of these trees experienced either natural winter snowpack or five consecutive years in which we removed early winter snowpack. When we sanded the cores and viewed them under a microscope, they revealed annual growth rings that we could use to understand how each tree responded to its environment.
Within just the first two years, our analyses showed a 40 percent decline in sugar maple growth from plots without snowpack. Growth rates remained depressed by 40 to 55 percent over the next three years. By contrast, there was no growth decline in the sugar maple trees in our reference plots where snow covered trees' roots in midwinter. These results are comparable to root mortality that other researchers observed in an earlier snow removal experiment at Hubbard Brook.
At Hubbard Brook, sugar maples can account for more than half of annual forest biomass accumulation. Consequently, changes in climate that reduce winter snowpack and increase soil freezing could reduce forest growth rates in the northern hardwood forest region by 20 percent just through their impacts on these trees. But we know that yellow birch also suffers root damage in response to soil freezing, so our estimate for changes in whole forest growth is likely to be low.
Removing a tree core with an increment borer Andrew Reinmann, CC BY-ND
Could warmer growing season temperatures compensate at least partially for this damage by stimulating rates of tree growth, as some research suggests? Very little work has been done to understand how forests in seasonally snow-covered regions will respond to interactive effects of climate change across seasons. To help fill this gap, we established the Climate Change Across Seasons Experiment at Hubbard Brook in 2013.
In this project we use buried heating cables to warm forest soils by 9 degrees Fahrenheit (5 degrees Celsius) during the snow-free season from April through November. In winter we use a combination of warming with buried heating cables and snow shoveling to induce soil freeze-thaw cycles. Our results so far show that root damage and reduced tree growth caused by winter soil freeze-thaw cycles are not offset by soil warming during the growing season.
Our work shows how often-overlooked changes in winter climate can impact forest ecosystems. 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.
40 Scientists: Protecting #Forests Is an Urgent Climate Issue #TuesdayThoughts #TuesdayMotivation https://t.co/lXppfDYQtW— EcoWatch (@EcoWatch)1539094222.0
Andrew Reinmann is an assistant professor at CUNY Graduate Center. Pamela Templer is a professor at Boston University.
Disclosure statement: Andrew Reinmann receives funding from the U.S. Environmental Protection Agency. Pamela Templer has received funding from the National Science Foundation, National Oceanic and Atmospheric Administration, United States Department of Agriculture, and U.S. Geological Survey. She is on the governing board of the Ecological Society of America.
Reposted with permission from our media associate The Conversation.
EcoWatch Daily Newsletter
Coronavirus Shines Light on Zoos as Danger Zones for Deadly Disease Transmission Between Humans and Animals
By Marilyn Kroplick
The term "zoonotic disease" wasn't a hot topic of conversation before the novel coronavirus started spreading across the globe and upending lives. Now, people are discovering how devastating viruses that transfer from animals to humans can be. But the threat can go both ways — animals can also get sick from humans. There is no better time to reconsider the repercussions of keeping animals captive at zoos, for the sake of everyone's health.
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By Kate Whiting
Bernice Dapaah calls bamboo "a miracle plant," because it grows so fast and absorbs carbon. But it can also work wonders for children's education and women's employment – as she's discovered.
These are the world's most bicycle-friendly cities. Statista<p>"The reason we use bamboo to manufacture bicycles is because it's found abundantly in Ghana and this is not a material we're going to import," says Dapaah, one of the World Economic Forum's Young Global Leaders.</p><p>"It's a new innovation. There were no existing bamboo bike builders in our country, so we were the first people trying to see how best we could utilize the abundant bamboo in Ghana."</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="a335b5dffdd806bd6bb4debea90c2045"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/dxsb9c4HMn0?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Supporting Students<p>Besides encouraging Ghanaians to swap vehicles for affordable bikes, Ghana Bamboo Bikes Initiative is helping students save time on walking to school so they have more time to learn.</p><p>Each time they sell a bike, they donate a bike to a schoolchild in a rural community, who might otherwise have to walk for hours to get to school.</p><p>Dapaah knows how transformative a shorter journey to school can be to academic performance. She grew up living with her <a href="https://www.youtube.com/watch?v=sb3joGYmx9A&feature=emb_logo" target="_blank">grandpa, a forester in a rural part of the country</a>.</p><p>"We had to walk three and a half hours every day before I could go to school. He later bought me a bike, so I finished senior high and wanted to go to university."</p><p>The experience inspired her to launch Ghana Bamboo Bikes Initiative with two other students at college.</p><p>"When we started this initiative, I looked back and said, when I was young, I had to walk miles before I could get to school, and sometimes if I was late, I was punished.</p><p>"Why don't we donate bikes for students to encourage them to study and so they can have enough time to be on books."</p><p>To date, they have sold more than 3,000 road, mountain and children's bikes – and Dapaah says they plan to donate <a href="https://www.entrepreneur.com/video/350343" target="_blank">10,000 bikes to schoolchildren over five years</a>.</p>
Empowering Women<p>The enterprise is also providing local jobs. It teaches young people to build bikes, particularly women and those in rural communities, where jobs can be scarce. More than 50% of people they have trained are women.</p><p>Dapaah says they want to boost the number of people they employ to 250 over the next five years and they are looking to partner with NGOs to build a childcare facility so mothers can continue to work.</p>
Reducing Emissions<p>By promoting a cycling culture in Ghana, Dapaah says they're also committed to reducing emissions in the transport sector and contributing to the UN's Sustainable Development Goals.</p><p>"I love the idea of reusing bamboo to promote sustainable cycling. People want to go green, low-carbon, lean-energy efficient," she says.</p>
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Deforestation coupled with the rampant destruction of natural resources will soon have devastating effects on the future of society as we know it, according to two theoretical physicists who study complex systems and have concluded that greed has put us on a path to irreversible collapse within the next two to four decades, as VICE reported.
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By Kristen Pope
Melting and crumbling glaciers are largely responsible for rising sea levels, so learning more about how glaciers shrink is vital to those who hope to save coastal cities and preserve wildlife.
Groans, Creaks, Icebergs’ Calving Splashes<p>Oskar Glowacki already knew that melting glacial ice sounds like frying bacon. As ice bubbles burst, anyone nearby can hear crackling and popping, said Glowacki, a postdoctoral scholar at the Scripps Institution of Oceanography. Using hydrophones, he and other scientists now can make more nuanced measurements of how a changing climate sounds underwater, from the groans, creaks and splashes of a calving iceberg to the changes in whale songs as the ocean warms.</p><p>Glowacki recently used a pair of hydrophones to study the underwater world of glaciers, publishing his findings in <a href="https://www.the-cryosphere.net/14/1025/2020/" target="_blank">The Cryosphere</a>. He and co-author Grant B. Deane measured glacier retreat by <a href="https://yaleclimateconnections.org/2020/07/melting-glaciers-sound-like-frying-bacon/" target="_blank">recording the sounds of ice</a> – from small chunks to enormous slabs – falling off the glacier and splashing into the water.</p><p>During the summer of 2016, Glowacki's team placed two hydrophones near Hansbreen Glacier in Hornsund Fjord, Svalbard. For a month and a half, they recorded sounds, also using three time-lapse cameras to collect images – including the "drop height" (how far the ice fell into the water) – so they could compare photos to the recordings. The team created a formula to represent the relationship between the size of a piece of ice falling from a glacier and the sound it makes underwater, also accounting for the pieces of ice falling from varying heights. (Hear an example of the sound an iceberg makes while calving <a href="https://soundcloud.com/user-248456662/iceberg-calving-hansbreen-glacier" target="_blank">here</a>.)</p>
Unlocking Information About Antarctic Ice Shelf<p>Other researchers also are using hydrophones to learn more about crumbling glaciers. Bob Dziak, research oceanographer with the NOAA/Pacific Marine Environmental Laboratory <a href="https://www.pmel.noaa.gov/acoustics" target="_blank">acoustics research group</a>, captured a massive calving event of the Nansen Ice Shelf in Antarctica with a hydrophone. He published the results with colleagues in <a href="https://www.frontiersin.org/articles/10.3389/feart.2019.00183/full" target="_blank">Frontiers in Earth Science</a></p><p>On April 7, 2016, satellite images showed a massive calving event had occurred on the ice shelf. The paper described it as the "first large scale calving event in >30 years."</p><p>However, once Dziak and colleagues delved into the data from three hydrophones deployed 60 kilometers east of the ice shelf, they uncovered a series of "icequakes" from January to early March 2016. He and other researchers believe that much of the ice actually broke free in mid-January to February, but it remained in the same location until an April storm – which their paper described as the "largest low-pressure storm recorded in the previous seven months" – broke the ice free.</p><p>"We suspected that the icebergs broke apart but remained in place – kind of pinned in place – until a major storm with high winds passed through the area and, finally, it was that last push that pushed the icebergs out to sea," Dziak says.</p><p>He and his co-authors wrote that "fortuitous timing and proximity of the hydrophone deployment presented a rare opportunity to study cryogenic signals and ocean ambient sounds of a large-scale ice shelf calving and iceberg formation event."</p>
Listening to Songs of Humpback Whales<p><a href="https://www.mbari.org/" target="_blank">Monterey Bay Aquarium Research Institute</a> studies the ocean, including its acoustics. One of the institute's projects involves examining the soundscape of California's Monterey Bay, including sounds from animals, humans, weather, and geologic processes like earthquakes. The researchers once even recorded an under-sea landslide. They also focus on recording and analyzing the <a href="http://www.mbari.org/humpback-song/" target="_blank">songs of humpback whales</a>. Male humpback whales' songs can be over 15 minutes in length, and they can be repeated for long periods of time – even hours. Listening to these songs and analyzing them can provide unique insights into the lives of these complex animals.</p><p>"Any time we want to study marine mammals, sound gives us a window into their lives because they use sound for all of their essential life activities, really," says institute biological oceanographer John Ryan. "Communication, foraging, reproduction, navigation – depending on the species, of course."</p><p>Previously, scientists had thought singing occurred only during courtship and mating, but now they think whales may also use song while migrating and hunting. They know song has a crucial role in the whales' lives.</p><p>"There's a whole other dimension to humpback whale song," Ryan says. "It is a mode of cultural transmission in this species. They learn songs from each other. They share songs as a population, and when populations mix and mingle, they learn new ideas, they explore with their song, improvise, and it's a real essential part of their culture."</p>
By William S. Lynn, Arian Wallach and Francisco J. Santiago-Ávila
A number of conservationists claim cats are a zombie apocalypse for biodiversity that need to be removed from the outdoors by "any means necessary" – coded language for shooting, trapping and poisoning. Various media outlets have portrayed cats as murderous superpredators. Australia has even declared an official "war" against cats.
Faulty Scientific Reasoning<p>In our <a href="https://doi.org/10.1111/cobi.13527" target="_blank">most recent publication</a> in the journal Conservation Biology, we examine an error of reasoning that props up the moral panic over cats.</p><p>Scientists do not simply collect data and analyze the results. They also establish a logical argument to explain what they observe. Thus, the reasoning behind a factual claim is equally important to the observations used to make that claim. And it is this reasoning about cats where claims about their threat to global biodiversity founder. In our analysis, we found it happens because many scientists take specific, local studies and overgeneralize those findings to the world at large.</p><p>Even when specific studies are good overall, projecting the combined "results" onto the world at large can cause unscientific overgeneralizations, particularly when <a href="https://doi.org/10.1016/j.tree.2015.01.003" target="_blank">ecological context is ignored</a>. It is akin to pulling a quote out of context and then assuming you understand its meaning.</p>
Ways Forward<p>So how might citizens and scientists chart a way forward to a more nuanced understanding of cat ecology and conservation?</p><p>First, those examining this issue on all sides can acknowledge that both the well-being of cats and the survival of threatened species are legitimate concerns.</p><p>Second, cats, like any other predator, affect their ecological communities. Whether that impact is good or bad is a complex value judgment, not a scientific fact.</p><p>Third, there is a need for a more rigorous approach to the study of cats. Such an approach must be mindful of the importance of ecological context and avoid the pitfalls of faulty reasoning. It also means resisting <a href="https://doi.org/10.1111/cobi.13126" target="_blank">the siren call of a silver (lethal) bullet</a>.</p>
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