9 Facts That Will Change How You Think About Sharks
By Jen Sawada
Sharks have been around for 400 million years, before the time of the dinosaurs, but there's much more to them than big teeth and summer blockbusters. Consider these facts, which will change what you think about sharks.
No Need to Fear the World’s Biggest Shark
Whale sharks are gentle giants of the ocean, often growing as long as 40 feet. They swim with their mouths open to filter-feed on small fish, invertebrates and plankton. While whale sharks aren't seen on Shark Week as often as jagged-toothed great whites are, they do attract large audiences of divers—contributing about $47.5 million worldwide each year.
Some Sharks Can Walk
There's a shark species found off the coast of Indonesia that doesn't just swim around. It gets from place to place by walking on the ocean floor.
Rays Are Flat Sharks
Though they look different, rays are closely related to sharks—so closely, in fact, that they're often referred to as flat sharks. These species have cartilage skeletons and float through the water thanks to their oil-rich liver—not the swim bladder on which other fish rely. Mobula rays, pictured above and manta rays have received protections through the Convention on International Trade in Endangered Species of Wild Fauna and Flora.
This Shark Has Many Names—Just Don’t Call Him ‘Jaws’
You've heard of a great white shark, but what about a white or blue pointer? Turns out, they're all the same species! In Australia, the world's most famous shark is called a white pointer, while in South Africa, it's a blue pointer.
Greenland Sharks Are the World’s Longest-Living Vertebrate
NOAA Okeanos Explorer Program
Last year, scientists discovered a Greenland shark estimated to be 400 years old. That makes this species the oldest known living vertebrate. These slow-growing sharks don't reach reproductive age until around 150, so it's fortunate that they have a long life span to make up for lost time.
Many Sharks Give Birth Like Mammals
Have you ever seen a shark give birth? This may come as a surprise, but many shark species give birth to live young instead of laying eggs. That makes them more like mammals than other fish. Researchers released a video in 2015 of what they think is the first thresher shark birth caught on camera.
Blue Sharks Top the Fin Trade
These sleek indigo sharks are found in nearly all the world's oceans—and are also the most caught. About 20 million blue sharks are killed every year, most of them for their fins. This heavy fishing has caused their numbers to drop sharply. Fortunately, Samoa and Sri Lanka have proposed giving blue sharks protections through the Convention on Migratory Species (CMS). Other shark species that could receive protections through CMS this year are whale sharks, dusky sharks, wedgefish, guitarfish and angel sharks.
Sharks Prove You Can Go Home Again
There's no place like home. There's no place like home. Sharks don't have ruby slippers to help them get home, but some species have an amazing innate ability called philopatry, the tendency to return to where they started their lives. Female lemon sharks, for example, swim all the way back to where they were born in The Bahamas to give birth to their young. The island chain is one of 15 shark sanctuaries worldwide, where sharks are safe from commercial fishing.
There Are Some Very Surprising Sharks in the Sea
It's a coral! It's a carpet! It's a … shark? The tasseled wobbegong is one of the more unusual sharks in the ocean, but this bottom-dweller isn't the only unexpected species swimming around reefs. There are more than 500 species of sharks in the world's oceans—and there may be many more that scientists still have not identified.
Jen Sawada is an officer for Pew's global shark conservation campaign, managing efforts to encourage countries in the Pacific and Caribbean to adopt domestic measures to protect sharks, including creating shark sanctuaries.
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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:firstname.lastname@example.org" 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.