
For birders and fans of Hedwig from the Harry Potter series, spotting a snowy owl in the wild is a special treat as these great white raptors spend most of their lives in the Arctic.
But sightings further south have become more common in North America in recent winters. As the Ottawa Citizen reported this week, sightings of the charismatic owl have soared in Eastern Ontario for the last six years.
This "irruption"—an influx of a species to areas they aren't usually found—could be a sign that there's not enough food for the snowies around their usual home.
Because of climate change, the Arctic is warming at twice the rate of the rest of the planet, causing dramatic shifts to ecosystems. This warmth has caused the region to become more green.
As a result, rodents have more vegetation to graze on, thus increasing the prey base for snowy owls. This abundance in prey, a bird expert suggested to Ottawa Citizen, has resulted in successful breeding seasons for the snowy owls. But with more owls hunting in the same area, the less successful hunters end up traveling south in search of food.
"It could be climate change: The Arctic warming up, more vegetation available, so it's producing more rodents," birder Bruce Di Labio told the Ottawa Citizen. "In turn, the snowy owls are being successful (in breeding) every year."
The Audobon Society explains that "it's all about food availability: when the birds' rodent prey base either crashes or is in super-abundance, snowy owls push south in winter."
Over time, however, these southern sightings could be a much rarer occurrence:
"Audubon's climate model suggests that in the future such southward excursions may become less extensive. By century's end, climatically suitable areas for wintering Snowy Owls may have pushed north from southern Canada well into the Arctic. The big question for these owls isn't climate per se—these big predators can withstand harsh weather—but, rather, the indirect effect of climate on the owls' prey base."
Although snowy owl populations are linked to booms and busts of Arctic rodents, the bird's numbers are in steep decline overall, Smithsonian magazine reported. In the December 2017 Red List of Threatened Species, the bird's status was listed as "vulnerable" for the first time. Its population is currently around 28,000 birds, down from 200,000 in 2013.
Andy Symes, global species officer of BirdLife International, warns that the worsening effects of climate change could put the species at a high risk of extinction in the wild in the medium-term future.
"The dramatically revised population estimates are a further source for concern, and the species must now be a high priority for further research and conservation action," Symes said.
52 Percent of World's Birds of Prey Populations in Decline @wwf @nwf @defenders @janegoodallinst… https://t.co/vwAu9aXrY4— EcoWatch (@EcoWatch)1536733451.0
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By Katherine Kornei
Clear-cutting a forest is relatively easy—just pick a tree and start chopping. But there are benefits to more sophisticated forest management. One technique—which involves repeatedly harvesting smaller trees every 30 or so years but leaving an upper story of larger trees for longer periods (60, 90, or 120 years)—ensures a steady supply of both firewood and construction timber.
A Pattern in the Rings
<p>The <a href="https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/coppice-standards-0" target="_blank">coppice-with-standards</a> management practice produces a two-story forest, said <a href="https://www.researchgate.net/profile/Bernhard_Muigg" target="_blank">Bernhard Muigg</a>, a dendrochronologist at the University of Freiburg in Germany. "You have an upper story of single trees that are allowed to grow for several understory generations."</p><p>That arrangement imprints a characteristic tree ring pattern in a forest's upper story trees (the "standards"): thick rings indicative of heavy growth, which show up at regular intervals as the surrounding smaller trees are cut down. "The trees are growing faster," said Muigg. "You can really see it with your naked eye."</p><p>Muigg and his collaborators characterized that <a href="https://ltrr.arizona.edu/about/treerings" target="_blank">dendrochronological pattern</a> in 161 oak trees growing in central Germany, one of the few remaining sites in Europe with actively managed coppice-with-standards forests. They found up to nine cycles of heavy growth in the trees, the oldest of which was planted in 1761. The researchers then turned to a historical data set — more than 2,000 oak <a href="https://eos.org/articles/podcast-discovering-europes-history-through-its-timbers" target="_blank" rel="noopener noreferrer">timbers from buildings and archaeological sites</a> in Germany and France dating from between 300 and 2015 — to look for a similar pattern.</p>A Gap of 500 Years
<p>The team found wood with the characteristic coppice-with-standards tree ring pattern dating to as early as the 6th century. That was a surprise, Muigg and his colleagues concluded, because the first mention of this forest management practice in historical documents occurred only roughly 500 years later, in the 13th century.</p><p>It's probable that forest management practices were not well documented prior to the High Middle Ages (1000–1250), the researchers suggested. "Forests are mainly mentioned in the context of royal hunting interests or donations," said Muigg. Dendrochronological studies are particularly important because they can reveal information not captured by a sparse historical record, he added.</p><p>These results were <a href="https://www.nature.com/articles/s41598-020-78933-8" target="_blank">published in December in <em>Scientific Reports</em></a>.</p><p>"It's nice to see the longevity and the history of coppice-with-standards," said <a href="https://www.teagasc.ie/contact/staff-directory/s/ian-short/" target="_blank">Ian Short</a>, a forestry researcher at Teagasc, the Agriculture and Food Development Authority in Ireland, not involved in the research. This technique is valuable because it promotes conservation and habitat biodiversity, Short said. "In the next 10 or 20 years, I think we'll see more coppice-with-standards coming back into production."</p><p>In the future, Muigg and his collaborators hope to analyze a larger sample of historic timbers to trace how the coppice-with-standards practice spread throughout Europe. It will be interesting to understand where this technique originated and how it propagated, said Muigg, and there are plenty of old pieces of wood waiting to be analyzed. "There [are] tons of dendrochronological data."</p><p><em><a href="mailto:katherine.kornei@gmail.com" target="_blank" rel="noopener noreferrer">Katherine Kornei</a> is a freelance science journalist covering Earth and space science. Her bylines frequently appear in Eos, Science, and The New York Times. Katherine holds a Ph.D. in astronomy from the University of California, Los Angeles.</em></p><p><em>This story originally appeared in <a href="https://eos.org/articles/tree-rings-reveal-how-ancient-forests-were-managed" target="_blank">Eos</a></em> <em>and is republished here as part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story.</em></p>Earth's ice is melting 57 percent faster than in the 1990s and the world has lost more than 28 trillion tons of ice since 1994, research published Monday in The Cryosphere shows.
By Jewel Fraser
Noreen Nunez lives in a middle-class neighborhood that rises up a hillside in Trinidad's Tunapuna-Piarco region.