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By Marlene Cimons
Neil Pederson's introduction to tree rings came from a "sweet and kindly" college instructor, who nevertheless was "one of the most boring professors I'd ever experienced," Pederson said. "I swore tree rings off then and there." But they kept coming back to haunt him.
As a future forest ecologist, he needed to learn more about the history of forests. So he read countless articles in graduate school extolling the importance of tree rings in unraveling a forest's past. Ultimately, "I fell in love with the beauty and wealth of information found in tree rings," he said. "Since then, tree rings have revealed to me the absolute resiliency of trees and forests. I'm hooked."
Today, he and his colleagues are using the data inherent in these ancient sources of nature to better understand the impact of climate change and carbon dynamics on forests, all the more valuable because data from long-lived trees can reach back decades, even centuries. This is far longer than modern satellite imagery, carbon dioxide measurements, and computer models, whose high-tech information gathering only stretches back about 30 years.
"What tree rings can do is enhance those records," Pederson said. "The satellite record … represents a small portion of the life of a tree, let alone the 'life' of a forest. Further, it only captures the weather 'norm' for a region and, as we are learning, climate varies over time. The weather norms or averages on your nightly weather reports are based on 30-year means. So, while satellite records are good at covering space, they might be limited in what they can tell us about forests due to shortness of these records."
Scientists sampling tulip-poplar at the Black Rock Forest in southern NY.
Neil Pederson / Harvard University
Pederson, now a senior ecologist with Harvard University's Harvard Forest, a 4,000-acre research site, along with Laia Andreu-Hayles, an associate research professor at Lamont-Doherty Earth Observatory of Columbia University, and Mathieu Levesque, research leader of the forest management group at ETH Zurich, analyzed tree rings to determine if the information they gleaned matched the accuracy of high-tech equipment. They wanted to know whether the rings could serve as a proxy for learning more about carbon storage and climate change in forests over the long-term, and found that they could.
Forests serve as important carbon "sinks," absorbing planet-heating carbon dioxide that has been released into the atmosphere by the burning of fossil fuels. But little is known about exactly how much carbon is stored in forests now, or in the past, and scientists are only in recent years learning about the past effects of climate change.
The scientists examined ring samples from two widespread species — tulip poplar (Liriodendron tulipifera) and northern red oak (Quercus rubra) — growing in three climatically different regions of the eastern U.S., then analyzed the carbon and oxygen molecules — or stable isotopes — stored in them. They compared them to estimates obtained from satellites, and found strong agreement each year, and over time. No trees were destroyed to obtain the rings, by the way. Rather, scientists remove an increment core for each sample, each slightly narrower than a pencil.
"Our study is the first to compare stable isotopes from tree rings with the latest generations of productivity estimates from satellites," Levesque said. "We took advantage of the newly developed satellite data, and this is the main novelty of our study."
Their findings appear in the journal Nature Communications.
Flower of tulip-poplar, the tallest documented tree in the eastern U.S.
Neil Pederson / Harvard University
"Tulip poplar trees, one of my favorite trees, are highly sensitive to rainfall," Pederson said. "In fact, they are considered drought deciduous. (These are plants that drop their leaves during dry or drought periods.) During the drought in 1999 in the New York City area, some tulip poplars turned yellow in August and dropped many of their leaves due to the dryness of the year. In 2005, in Kentucky, after a drought in August, the three tulip poplars I walked by every day to work started to grow new leaves in September with the return of rain. I was stunned. These observations made me think this species might be a good candidate [to study.]"
Tulip poplar is highly sensitive to the amount of water in the soil, Pederson said. Also, he added, "it is an important species for timber and ecology over a large portion of the eastern U.S. … We [also] chose the stalwart, northern red oak, because of its different physiology, importance as a species, and its value as a study species in understanding forest productivity."
Levesque agreed. "Both species are great to study," he said. "Their wide distribution in eastern North America and their sensitivity to climate make them ideal species for our research." Moreover, "annual tree rings act like a thermometer and rain gauge and record climate in a very good way," he added.
The rings, in fact, revealed that access to water was the biggest influence in annual forest growth, regardless of climate. "These broadleaf trees need moisture to grow," Andreu-Hayles said. "Some people may think that in wet regions, moisture will be not important, but our study found that even in very humid time periods, as today, these trees are still sensitive to moisture variations. The stable isotopes measured in tree rings are highly sensitive to tracking moisture."
Levesque agreed. "Moisture availability is one of the most important factors for temperate forest growth in the northeastern, southeastern and central U.S.," he said. "That does not mean more moisture [means] more growth, because too wet conditions can also be a limiting factor. By 'regardless of climate,' we simply meant that moisture was the main limiting factor for tree growth and productivity irrespective of the local climate conditions found at the study sites."
Scan of the rings and wood structure of one of the tulip-poplar samples used in the study.
Mathieu Levesque / Harvard University
This is important because climate change has ushered in an era characterized by dramatic increases in extreme weather events, including prolonged drought, heavy precipitation and flooding and dangerous heat waves, thus more information about historic climate fluctuations could be useful in projecting future climate effects on forests. Experts regard the health of forests as a critical factor in mitigating carbon pollution.
Pederson noted that droughts in the 16th and 17th centuries were believed to be far worse than those in recent centuries, but it could be that climate change — by prompting more intense precipitation in some regions — has made the earlier droughts seem severe in comparison, he said. "The important thing to remember, however, is even though it is expected to rain more in the northeastern and eastern U.S. in the future, the warming associated with climate change will increase evaporation and the drought stress on plants," Pederson said. "It is not clear what will happen."
It's possible that as parts of the world become wetter, and warming reduces the overall amount of water in the region during the summer, it will worsen droughts, he said. Or it will become so wet that a rise in warming will balance the increase in precipitation, he said. Or — if rain decreases — the increase in warming will amplify the drought stress in trees, even if it doesn't seem as if the amount of available water has changed, he said.
The researchers hope to expand their research, examining more trees and additional species, and to look further back in time. "This kind of work will be extremely important considering that the longest remote sensing data started in 1982, and trees can live centuries-long," Andreu-Hayles said.
Pederson agreed. "These kinds of studies will provide considerable insight into how these trees will respond to climate and extreme climatic events … We can learn a lot from the memories of trees," he said.
Reposted with permission from our media associate Nexus Media.
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By Jennifer Molidor, PhD
Climate change, habitat loss and pollution are overwhelming our planet. Thankfully, these enormous threats are being met by a bold new wave of environmental activism.
Trump Makes Strange Claim About Water Efficient Toilets: 'People Are Flushing Toilets 10 Times, 15 Times'
President Donald Trump mocked water-efficiency standards in new constructions last week. Trump said, "People are flushing toilets 10 times, 15 times, as opposed to once. They end up using more water. So, EPA is looking at that very strongly, at my suggestion." Trump asked the Environmental Protection Agency (EPA) for a federal review of those standards since, he claimed with no evidence, that they are making bathrooms unusable and wasting water, as NBC News reported.
By Carey Gillam
Former Monsanto Chairman and CEO Hugh Grant will have to testify in person at a St. Louis-area trial set for January in litigation brought by a cancer-stricken woman who claims her disease was caused by exposure to the company's Roundup herbicide and that Monsanto covered up the risks instead of warning consumers.
A powerful volcano on Monday rocked an uninhabited island frequented by tourists about 30 miles off New Zealand's coast. Authorities have confirmed that five people died. They expect that number to rise as some are missing and police officials issued a statement that flights around the islands revealed "no signs of life had been seen at any point,", as The Guardian reported.
"Based on the information we have, we do not believe there are any survivors on the island," the police said in their official statement. "Police is working urgently to confirm the exact number of those who have died, further to the five confirmed deceased already."
The eruption happened on New Zealand's Whakaari/White Island, an islet jutting out of the Bay of Plenty, off the country's North Island. The island is privately owned and is typically visited for day-trips by thousands of tourists every year, according to The New York Times.
My god, White Island volcano in New Zealand erupted today for first time since 2001. My family and I had gotten off it 20 minutes before, were waiting at our boat about to leave when we saw it. Boat ride home tending to people our boat rescued was indescribable. #whiteisland pic.twitter.com/QJwWi12Tvt— Michael Schade (@sch) December 9, 2019
Michael Schade / Twitter
At the time of the eruption on Monday, about 50 passengers from the Ovation of Seas were on the island, including more than 30 who were part of a Royal Caribbean cruise trip, according to CNN. Twenty-three people, including the five dead, were evacuated from the island.
The eruption occurred at 2:11 pm local time on Monday, as footage from a crater camera owned and operated by GeoNet, New Zealand's geological hazards agency, shows. The camera also shows dozens of people walking near the rim as white smoke billows just before the eruption, according to Reuters.
Police were unable to reach the island because searing white ash posed imminent danger to rescue workers, said John Tims, New Zealand's deputy police commissioner, as he stood next to Prime Minister Jacinda Ardern in a press conference, as The New York Times reported. Tims said rescue workers would assess the safety of approaching the island on Tuesday morning. "We know the urgency to go back to the island," he told reporters.
"The physical environment is unsafe for us to return to the island," Tims added, as CNN reported. "It's important that we consider the health and safety of rescuers, so we're taking advice from experts going forward."
Authorities have had no communication with anyone on the island. They are frantically working to identify how many people remain and who they are, according to CNN.
Geologists said the eruption is not unexpected and some questioned why the island is open to tourism.
"The volcano has been restless for a few weeks, resulting in the raising of the alert level, so that this eruption is not really a surprise," said Bill McGuire, emeritus professor of geophysical and climate hazards at University College London, as The Guardian reported.
"White Island has been a disaster waiting to happen for many years," said Raymond Cas, emeritus professor at Monash University's school of earth, atmosphere and environment, as The Guardian reported. "Having visited it twice, I have always felt that it was too dangerous to allow the daily tour groups that visit the uninhabited island volcano by boat and helicopter."
The prime minister arrived Monday night in Whakatane, the town closest to the eruption, where day boats visiting the island are docked. Whakatane has a large Maori population.
Ardern met with local council leaders on Monday. She is scheduled to meet with search and rescue teams and will speak to the media at 7 a.m. local time (1 p.m. EST), after drones survey the island, as CNN reported.
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