Issued on: 08/09/2020 – 18:18Modified: 08/09/2020 – 18:16
Trees that grow quickly die younger, risking a release of carbon dioxide that challenges forecasts that forests will continue to be a “sink” for planet-warming emissions, scientists said Tuesday.
Tree cover absorbs a significant proportion of carbon dioxide emitted by burning fossil fuels and plays a crucial role in projections for our ability to wrestle down CO2 levels.
Researchers said current climate models expect forests to continue to act as a carbon sink through this century, with high temperatures and concentrations of CO2 thought to stimulate tree growth and so help them absorb more carbon as they mature quicker.
But in the study, led by England’s Leeds University and published in the journal Nature Communications, they warned that this faster growth was also linked to trees dying younger — suggesting increases in the role of forests as carbon storage may be “short lived”.
The researchers examined more than 200,000 tree-ring records from tree species across the globe and found that trade-offs between growth and lifespans occurred in almost all of them, including tropical trees.
Society has benefitted from the increasing ability of forests to soak up carbon in recent decades, said co-author Steve Voelker, from the State University of New York College of Environmental Science and Forestry, in a Leeds University statement.
But these CO2 uptake rates are “likely to be on the wane as slow-growing and persistent trees are supplanted by fast-growing but vulnerable trees”, he added.
“Our findings, very much like the story of the tortoise and the hare, indicate that there are traits within the fastest growing trees that make them vulnerable, whereas slower growing trees have traits that allow them to persist,” he said.
The researchers said the findings suggest that the chances of dying increase dramatically as trees reach their maximum potential size.
But they said it might also be that fast-growing trees invest less in defences against diseases or insect attacks, or are more vulnerable to drought.
Earth’s average surface temperature has risen just over one degree Celsius above pre-industrial levels, enough to boost the severity of droughts, heatwaves and superstorms made more destructive by rising seas.
– Sink or source? –
Commenting on the study David Lee, professor of atmospheric Science, at England’s Manchester Metropolitan University, said Earth system climate models currently predict the carbon storage of forests to continue or increase.
“This study shows the opposite, that increased CO2 compromises forests as a carbon sink,” he said.
That suggests the idea that “fossil-fuel based emissions can be ‘offset’ by planting trees (or avoiding deforestation) really does not stand up to scientific scrutiny”, he added.
But Keith Kirby, woodland ecologist at the University of Oxford, said it was not necessarily the case that forests would reverse their carbon role.
“We cannot rely as much on increased growth per unit area to maintain and enhance the forest carbon sink potential, but this might be offset by slowing deforestation and increasing the expansion of the extent of forests where this can be done in a sustainable way,” he said.
Global forests — and especially the tropics — soak up 25 to 30 percent of the planet-warming CO2 humanity spews into the atmosphere.
Last year, a football pitch of primary, old-growth trees was destroyed every six seconds, about 38,000 square kilometres (14,500 square miles) in all, according to Global Forest Watch.
© 2020 AFP
NASA Says Bus-Size Asteroid Narrowly Missed Earth Thursday – Voice of America
Scientists at the U.S. space agency NASA say a small asteroid – roughly the size of a bus – passed close to Earth on Thursday, flying just 22,000 kilometers above the surface, within the orbit of geostationary satellites that ring the planet.
While the proximity to Earth might raise alarm, scientists at NASA’s Jet Propulsion Laboratory (JPL) in Southern California said even if the asteroid had entered the earth’s atmosphere, it almost certainly would have broken up and become a bright meteor.
The asteroid, known as 2020 SW, is about five to ten meters wide and was first discovered on September 18 by the NASA-funded Catalina Sky Survey in Arizona.
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NASA’s Center for Near-Earth Object Studies (CNEOS) — part of the JPL — then did follow-up observations and confirmed its orbital trajectory, ruling out any chance of impact.
CNEOS director Paul Chodas says an object this size, this close to earth, is not uncommon. He says, “In fact, asteroids of this size impact our atmosphere at an average rate of about once every year or two.”
After passing the Earth, the asteroid will continue its journey around the Sun, not returning to Earth’s vicinity until 2041, when NASA says it will make a much more distant flyby.
The space agency says they believe there are over 100 million small asteroids like 2020 SW, but they are hard to discover unless they get very close to Earth.
In 2005, Congress assigned NASA the goal of finding 90 percent of the near-Earth asteroids that are about 140 meters or larger in size. These larger asteroids pose a much greater threat if they were to impact, and they can be detected much farther away from Earth, because they’re simply much brighter than the small ones.
Chodas says NASA’s asteroid surveys are getting better all the time, and the agency now expects to find asteroids the size of 2020 SW a few days before they come near Earth.
Bus-sized asteroid to pass close to the earth: NASA – Asia Times
As interstellar traffic goes, this is a close one.
The object, known as 2020 SW, will fly just 13,000 miles above the Earth’s surface on 24 September, NASA has said.
That is closer than the artificial objects that are in orbit around our planet, and power GPS, televisions and more — a close call, indeed.
The object was only discovered on the 18th of September by a NASA-funded project in Arizona, and further observations were able to track its trajectory and rule out any chance that it might collide with Earth, the report said.
After making its pass, it will then fly off to continue its trip around the solar system. It will not come back anywhere near Earth until 2041, when it will be at an even further distance.
The asteroid is thought to be about five to ten meters wide, roughly the size of a “small school bus,” the space agency said. The size is estimated from the brightness of the object, NASA said.
It is not expected to hit Earth — and if you’re reading this, it probably missed us.
However, if it were to hit, it would explode into a fireball as it made its way through the atmosphere, becoming a bright meteor of the kind that is sometimes visible from Earth’s surface, the report said.
Despite repeated suggests that the world is under threat from such asteroids, their visits are fairly common and never pose any great risk to people on Earth.
“There are a large number of tiny asteroids like this one, and several of them approach our planet as close as this several times every year,” said Paul Chodas, director of the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory in California.
“In fact, asteroids of this size impact our atmosphere at an average rate of about once every year or two.”
Experts have repeatedly suggested that asteroids more generally could pose more of a threat, and space agencies including NASA conduct “planetary defence” work intended to improve the chances of spotting an asteroid and dealing with any that might possible lead to any danger, the report said.
NASA has been tasked with finding 90% of the near-Earth asteroids that are 140 meters or bigger.
Such asteroids are far more dangerous than those akin to 2020 SW, since their larger size means they are able to make it through the atmosphere and potentially cause problems when they crash into Earth.
Their larger size also makes them easier to spot, however. There are many more smaller ones of sizes similar to 2020 SW, but their smaller size and lower brightness makes them difficult to see until they get close by.
“The detection capabilities of NASA’s asteroid surveys are continually improving, and we should now expect to find asteroids of this size a couple days before they come near our planet,” said Chodas.
Teenage British activist stages climate protest on Arctic ice floe – SaltWire Network
By Natalie Thomas
ABOARD ‘ARCTIC SUNRISE’ (Reuters) – Like many of her generation, Mya-Rose Craig feels strongly that adults have failed to take the urgent action needed to tackle global warming and so she has headed to the Arctic Ocean to protest.
Armed with a placard reading ‘Youth Strike for Climate”, the 18-year-old British activist is staging the most northerly protest in a series of youth strikes worldwide.
The strikes, made famous by Swedish campaigner Greta Thunberg, are resuming after a lull caused by the global coronavirus pandemic to draw public attention back to the threat posed by climate change.
“I’m here to… try and make a statement about how temporary this amazing landscape is and how our leaders have to make a decision now in order to save it,” she told Reuters Television as she stood with her placard on the edge of the Arctic sea ice.
“I absolutely think that my generation has always had to think about climate change… which is why as we’ve got older there’s been this massive wave of just this need for change, this demand for change when we realised the grown-ups aren’t going to solve this so we have to do it ourselves.”
Craig, from southwest England, is known as “Birdgirl” online, where her blog chronicling her bird-watching experiences has attracted thousands of followers.
She has travelled hundreds of miles above the Arctic Circle aboard a Greenpeace ship, Arctic Sunrise.
Climate data shows the Arctic is one of the fastest changing ecosystems on the planet, with serious consequences for wildlife from polar bears and seals to plankton and algae, while the melting sea ice contributes to rising sea levels worldwide.
Warming in the Arctic shrank the ice covering the polar ocean this year to its second-lowest extent in four decades, scientists said on Monday.
For Craig, getting to the ice floe involved a two-week quarantine in Germany, followed by a three-week voyage to the edge of the sea ice.
Craig said those who dismiss the youth protests as just a rebellious phase by her generation are wrong, and she wants those in power to stop treating climate change as a low-priority issue, raised only to appease “the lefties in the corner”.
“It’s everything now and it has to be treated like that,” she said.
(Reporting by Reuters Television; Writing by Gareth Jones; Editing by Janet Lawrence)
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