News Category: Science
Missing link uncovered in search for recycling on a cosmic scale
Researchers observe a dying pulsar reusing matter to revive itself
By Amy Minsky, Vancouver Sun – May 22, 2009
The green trend has, literally, reached cosmic proportions.
Researchers from McGill University and the University of British Columbia were among the first in the world to witness what they are calling a cosmic act of recycling.
A dying star was found to be using materials torn from a neighbouring star to increase its own speed and brightness.
PhD student Anne Archibald and her supervisor, McGill professor Victoria Kaspi, made the discovery while an international team of astrophysicists performed a survey of the sky. They were observing a system with one dying pulsar—a remnant from a stellar explosion—that was “gobbling up” material from a nearby companion star.
When Archibald and Kaspi’s team recently examined the system, they found the dying pulsar was spinning significantly faster than in 2000, when the transfer of materials was first observed by an independent research group.
Pulsars are highly magnetized neutron stars that spin moderately fast, but slow down as they age over a few thousand years.
“Pulsars are born spinning with a rotational speed of about 30 milliseconds,” Archibald said. “As they age, they slow down to a second or more, then eventually disappear.”
The pulsar Archibald and Kaspi observed was very old, yet spinning very quickly, with its rotational speed back into the milliseconds range.
“What they saw [in 2000] looked like it was in the middle of the recycling process,” Archibald said.
Based on those observations, Archibald said her team was able to confirm that the transferred materials had been recycled, and used to revive the pulsar by enabling it to increase its rotational speed.
Ingrid Stairs, an associate professor from UBC who contributes to this research, compared the process of the pulsar speeding up to that of a top.
“Before the process starts, the neutron star is spinning very slowly,” she said. “During recycling, matter that swirls onto it gives it a bit of a push and makes it spin faster, like a person’s fingers making a top spin faster.”
“This is very exciting,” said Marten Van Kerkwijk, a professor of astronomy and astrophysics at the University of Toronto. “We theorized that this was happening, and previous claims had been made about recycling, but they were always somewhat unbelievable. Now this is the real thing.”
In the past, astrophysicists had observed objects that appeared to be the product of recycling. But before Archibald’s discovery, Van Kerkwijk said, the recycling theory could not be confirmed.
Her team’s discovery offers an answer to the missing link in a pulsar’s transformation from an apparently dying star to a revived, spinning and bright pulsar, Archibald said.
Van Kerkwijk said the system will provide a “perfect example” for astrophysicists to understand the process by acting as a laboratory for studying the transfer of matter from one star to another, then the dying star’s renewal and rebirth.
N.W.T. fossils believed to be oldest evidence of animals
Traces of primitive organism found on mountaintop in Mackenzie range are thought to be about 850 million years old
By Randy Boswell, Vancouver Sun – May 6, 2009
Canadian scientists probing a mountaintop in the Northwest Territories have discovered what they believe is the oldest evidence of animals on Earth—about 850-million-year-old traces of a primitive, sponge-like organism that could push back direct proof of the origin of humanity’s own kingdom of life by an astonishing 200 million years.
The microscopic but distinctively patterned remains—unearthed from a dramatic pinnacle in the Mackenzie Mountains about 800 kilometres northwest of Yellowknife—are interpreted by the research team as rock-encased residues from the decomposed tissues of a primordial sea creature that was the earliest common ancestor of all animals, including humans. The organism, believed to have lived in the nooks of a reef from a long-lost ocean, represents a stage of life “before sponges and other animals we know today evolved,” University of Laval geologist Fritz Neuweiler, told Canwest News Service.
Experts in evolution have long postulated that animals must have been developing eons before the existence of known creatures that left easy-to-see skeletal fossils during the Cambrian and Ediacaran geological eras, reaching back about 635 million years ago.
“If you want to go back to the very origins of animals, you can’t be looking for that,” says Laurentian University paleontologist Elizabeth Turner, one of the three co-authors of a paper detailing the Canadian discovery in the latest issue of the journal Geology.
Arctic fossil is “missing link” to seals
By Randy Boswell, Vancouver Sun – April 23, 2009
A Canadian-led team of scientists working on a remote Arctic island has discovered the fossilized remains of an extinct forerunner of the modern seal—a stunning new species hailed as the “missing link” in land-to-sea evolution predicted by Charles Darwin.
The 20-million-year-old creature, unearthed on Nunavut’s Devon Island, was about one metre in length and possessed otter-like limbs and tail but the skull and jaw structure of a pinniped—the diverse family of marine mammals that includes members such as seals, sea lions and walruses.
Unveiled in the latest issue of Nature, the ancient animal is described as a semi-aquatic meat-eater with webbed feet adapted for speedy swimming, but also possessing nimble legs for hunting on land.
The discovery team—which is headed by Canadian Museum of Nature paleontologist Natalia Rybczynski and has also included the renowned, 77-year-old American scientist Mary Dawson—has labelled the find Puijila darwini: an Inuktitut word meaning “young sea mammal” followed by a Latinate tribute to Darwin.
The great British naturalist has been the focus of international celebrations this year to mark the 200th anniversary of his birth and the 150th anniversary of his landmark treatise on evolution, On the Origin of Species.
Darwin foretold the discovery of a transitional carnivore such as Puijila that would bridge the gap between land mammals with feet and marine mammals with flippers.
“A strictly terrestrial animal,” he wrote in the 1860s, “by occasionally hunting for food in shallow water, then in streams or lakes, might at last be converted into an animal so thoroughly aquatic as to brave the open ocean.”
Darwin observed: “We may believe that the progenitor of the seal did not possess a flipper, but a foot with five toes fitted for walking or grasping.”
Rybczynski said it appears Puijila lived in a freshwater habitat—fresh evidence to challenge the prevailing theory that pinnipeds moved directly from land to ocean to exploit saltwater prey.
Your Brain and Protein Power
As nerve cells develop, they grow connections and become integrated into neural networks that transmit electrochemical signals through the nervous system. Once these networks are established, a neuron’s capacity for growth and formation of new connections is diminished. This loss of neural plasticity is why an ageing or damaged brain is unable to repair itself by forming new connections.
But UBC researchers have discovered that neurons don’t lose their capacity for growth; rather, they are prevented from doing so. Researchers have pinpointed the agents involved in neural growth and suppression: the proteins calpain and cortactin. Cortactin activates neural growth, and calpain blocks cortactin once the neuron has developed and integrated into the nervous system.
The researchers were able to demonstrate in animal models that suppression of calpain results in greater neural plasticity. They are hopeful their discovery will lead to new treatments for neurological disorders and boost in the efficacy of treatments for other conditions.
Ana Mingorance-Le Meur, a postdoc in the department of Cellular and Physiological Sciences, is study lead along with professor Timothy O’Connor. “The maintenance of neuronal connections is an active process that requires constant repression of the formation of nerve sprouts by the protein calpain to avoid uncontrolled growth,” she says. “But a consequence of this role is that calpain limits
neural plasticity and the brain’s ability to repair itself. The next step is to find a way to enhance neural plasticity without interfering with the good connections that are already in place.” Mingorance-Le Meur is also a member of the Brain Research Centre at UBC and VCH Research Institute.
UBC Alumni’s Trek magazine Issue 23, Spring 2009 p 7
Rot and Human Health
Composting is good for the planet. But is it good for human health? As more cities adopt a mass composting policy, UBC researchers are trying to find the answer. “Even though it is an eco-friendly practice, we know biohazards may be present,” says associate professor Karen Bartlett of UBC’s school of Environmental Health. “There are disease-causing organisms present throughout the process.” The wastes can contain nasty microorganisms such as listeria and salmonella, but these break down as the waste heats up and decomposes.
Researchers at UBC are able to study three different composting technologies used in Vancouver, Kamloops and Kelowna. These also present different environmental conditions for the rocess. “We will be able to make recommendations to the composting industry, which could help prevent both acute effects and chronic lung disease,” says Jim Atwater, an associate professor of civil engineering.
On the front line are the five to 10 workers at each composting site. “Workers are exposed to massive blooms of organisms that can potentially cause lung damage in high doses,” says Bartlett. “We’ve seen studies from countries where composting is a bigger industry than in Canada. They show that some workers experience ill health associated with breathing organic dust.” Chronic health effects can include permanent scarring of the lungs.
Researchers are exploring what bearing different methods of composting have on human exposure to fungal spores, thermophilic spore-forming bacteria and endotoxins, and on the presence of disease-causing microorganisms. They are also considering environmental factors such as temperature and humidity, which have already been shown to make a difference. “The dry air in Kamloops and Kelowna has an impact on the dispersion of microorganisms and a buffer zone between the composting facility and other facilities may be required,” says Bartlett. “On the other hand, the amount of rain in Vancouver has an impact on dispersion and a buffer zone may not be required.” The researchers also want to establish if minimum temperatures for the destruction of disease-causing mircoorganisms are always met.
The project, which is funded by Worksafe BC, will be used to establish work safety practices.
UBC Alumni’s Trek magazine Issue 23, Spring 2009 p 5
Beetling About in Kelowna
When people think about pine beetle infestation, they usually think of vast tracts of dead forest. But pine beetles don’t limit their activities to rural areas, as Kelowna residents can testify. The city was hit with an infestation of the insect for the first time last summer. For UBC Okanagan researchers, this presented an opportunity to learn how the beetle moves and spreads through an urban area.
Bob Lalonde and Rebecca Tyson combined their expertise in biology and mathematics respectively to gather data and build a mathematical model that can identify dispersal patterns. “We are
trying to determine how the bark beetle enters the city, what direction they come from and how they move in the city,” says Lalonde. “In addition, we plan to study the beetles themselves and look at factors such as how much energy is being burned in their flight path.”
With two summer students, the researchers placed 44 pheromone traps around the city and its outskirts. They were left for two months and checked every week. Depending on location and the prevalence of natural predators (the work should also shed light on how quickly beetle predators follow their prey into new areas) the traps contained anywhere from zero to 200 beetles. Other variables used to create the dispersal model include concentration of pine trees, beetle biology and weather conditions.
“Mathematical modeling often reveals interesting behaviors that aren’t anticipated,” says Tyson, an assistant professor of mathematics, statistics and physics. “We are using beetle biology, spatial data and math in this research, which may help us gain insight into the risk of infection for pine trees in certain areas of the city. This could result in possible solutions or preventative measures.”
The team plans more data collection this summer. This time, the data may help reveal the number of beetles originating from the city rather than entering it. “There is still a lot of data to be collected and analyzed,” says Tyson. One thing we can say with confidence is that, based on early results, it looks as though bark beetles enter a city from the outskirts inward, as opposed to dropping randomly from above, as some people had originally suggested.”
UBC Alumni’s Trek magazine Issue 23, Spring 2009 p 11
New Patinas Bridge Science and Art
by Jody Jacob
Entirely new colours for metal patinas are being developed by UBC Okanagan fourth-year undergraduate Ashley Devantier and chemistry professor Stephen McNeil.
Imagine a purple Statue of Liberty dressed in a canary-yellow robe, holding a bright red flame.
The artistic concept is in the scientific works thanks to research by Ashley Devantier, a fourth-year UBC Okanagan student who is using chemistry to create more colour options for artists working with patinas.
A patina is a coloured coating on the surface of bronze or similar metals, often produced naturally by oxidation over a long period, such as the blue-green colour on the Statute of Liberty’s copper surfaces. Artificial patinas are used by artists to add an antique look or feel to their artwork, but these artificial patinas have their drawbacks: they’re confined to a very limited colour palette (usually blue-green) and often use highly toxic or hazardous compounds.
By mixing and manipulating common – and far less toxic – metallic elements and identifying the molecular basis for new colours, Devantier has produced nearly a full rainbow of colours not previously available in the patina palette. In addition, she has studied and analyzed the underlying molecular changes that take place when applying these new patinas.
“I took some common metallic elements – chromium, iron, cobalt and copper – which are known to give compounds very intense, vibrant colours, and started to explore the chemical processes that occur when they are applied to bronze surfaces,” says Devantier. “All of a sudden these amazing colours started to show up.”
Although the practical applications are yet to be determined, Devantier’s research could potentially give artists new, less toxic formulas to create patinas of varying colours and an array of exciting options for their bronze art.
Devantier, who received an Undergraduate Research Award (URA) from the Irving K. Barber School of Arts and Sciences to conduct her research last summer, says interest in her work has been overwhelming and the experience itself has been life-changing.
“The response I’ve had from the internal UBC arts community is fantastic,” she says. “When I look at where I was only a few months ago and where this project has taken me, well, it’s mind-boggling. The URA grant has completely changed my personal path and the way I thought about science and research.”
Devantier had planned to finish her bachelor of science degree in chemistry by December. She was looking forward to finishing university and was eager to start working in whatever field she was able to land a job. But after receiving the URA and completing the research part of her project last summer, Devantier decided to continue with her project through an honours thesis.
“This project has been in Ashley’s hands since day one,” says Stephen McNeil, assistant professor of chemistry and primary supervisor of Devantier’s patina research project. “It is really something off the beaten path. I was surprised to find out that nobody has done the preliminary work to see what transition metals could be put on a surface to create colour, so it was very exploratory at the start. It’s a visually enticing project that bridges science and art.”
As part of her honours thesis, Devantier is studying molecular changes over time occurring on the surface of the bronze patinas, and recording them. The next step will be to approach the arts community to determine the practical applications of the research.
Although the project has been rewarding for Devantier, it has presented interesting challenges. “There was the great saga of the disappearing red,” she says. “I produced this beautiful bright red and for the life of me I couldn’t figure out how to do it again. I used the exact same mixture, and it would repeatedly turn blue. I was convinced the colour gods hated me.”
A few weeks of perseverance and careful study revealed the cause: solutions of an iron salt would react with the copper atoms in the bronze surface, yielding a red iron compound. If the iron solution had time to react with oxygen in the surrounding atmosphere, the iron complex would oxidize and form a blue colour instead. Applying the iron under a flow of nitrogen gas would prevent the oxidation, leaving the original red. Chemical identification of the blue and red materials provided the clues needed to reproduce each colour.
“Figuring that out was the most rewarding thing I’ve ever done,” says Devantier.
UBC ALumni’s Trek Magazine Issue #23: Spring 2009 pp 30-31
Canadians Like Their Comfort Foods
Researchers at UBC and Dalhousie University have found that Canadian families, regardless of ethnicity, take comfort in traditional foods. Their findings also suggest that despite the comfort, some food choices may lead to above-average risk for heart disease and diabetes.
UBC Nutrition Prof. Gwen Chapman and co-authors interviewed Canadians of European, Punjabi and African descents in British Columbia and Nova Scotia. Their three-year study is the first to explore the layered meanings of food choices in ethnic communities and will contribute to better health promotion and nutrition education.
The researchers found that most Nova Scotians of African descent value “black ways of eating,” choosing hot and spicy dishes or “soul food” as a way of asserting their cultural heritage.
In B.C., Punjabi families, especially new immigrants, routinely prepare two separate meals to accommodate elders who need dishes like roti, dahl and subjee to feel satisfied and younger family members who prefer to balance Indian and “Canadian” foods.
For families of European descent, “meat and potatoes” meals represent a source of comfort. However, they also place higher value than other communities on “healthy foods” as defined by nutritional
science.
reachout newsletter – UBC’s Faculty of Land and Food Systems Issue 11 Spring 2009
Scientists read minds with brain scanner
Thursday, March 12, 2009
CBC News
Scientists have found they can pinpoint the location of a person within a virtual room by reading his mind with a brain imaging device.
“Remarkably … we could tell where they were just by looking at the patterns of activity,” said researcher Eleanor Maguire at a news conference prior to the release of the results Thursday in the latest issue of Current Biology.
The researchers scanned the brains of volunteers using a technique called functional magnetic resonance (fMRI), which measures changes in blood flow within the brain, showing which areas are more active.
However, Demis Hassabis, who co-authored the paper with Maguire and several others, said scientists are at least 10 years away from being able to use the technique to determine whether someone is lying about where they have been.
It’s going to require a leap of technology advancement,” he said.
Maguire agreed, noting that the technique relies on the co-operation of the subject to train a computer to get familiar with their brain patterns.
“It’s quite an involved process that’s at a very early stage,” she said. “It’s probably quite … far away from having social and ethical and probably forensic implications.”
The results of the study do open up new avenues for understanding how other memories are coded in the brain, said Maguire, a professor at University College London. In the long term, that could help researchers understand how diseases such as Alzheimer’s erode memory and lead to new ways to help patients, she added.
In the study, Maguire and her colleagues asked four male, right-handed volunteers to navigate as quickly as possible 14 times between four positions in a virtual room while they were monitored with an fMRI scanner.
All subjects showed activity in the same area of the hippocampus, the area of the brain known to encode spatial memory.
Most trials for each location were used to “train” a computer. Based on the training, the computer was able to recognize the pattern for specific locations, allowing the researchers to predict where the volunteer was on the “non-training” runs.
Similar techniques had been used in vision neuroscience before, but not to study memory, Maguire said.
Previously, spatial memory had mostly been studied by looking at just a few neurons at a time in the hippocampi of rats.
Maguire said the fMRI doesn’t have very high spatial resolution, so the fact that it could pick out the patterns for different locations suggests that spatial memory is actually encoded over a far larger area than just a few neurons.
The study was funded by the Wellcome Trust, a medical research funding charity.
What is fMRI?
Functional magnetic resonance imaging is a technique that shows what parts of the brain are active by detecting changes in blood flow and the amount of oxygen consumed in different areas. Areas that are more active use more oxygen and therefore require more blood flow.
The scanner contains a strong magnet that causes particles inside the core atoms to line up in a certain way, producing a signal that is different for different kinds of atoms. In the case of MRI, the signal from hydrogen atoms in water is measured. The signal varies in different parts of the head, so that some parts appear darker than others.
An additional signal is detected in fMRI. Hemoglobin, the protein that carries oxygen in the blood, produces a slightly different signal when it is bound to oxygen, versus when it is not.
Memories of fear can be found and erased in mice, researchers show
Friday, March 13, 2009
The Canadian Press
In a scientific development that seems ripped from the script of the 2004 movie Eternal Sunshine of the Spotless Mind, Toronto researchers have shown they can find and selectively erase fear memories from the brains of mice.
The research is notable not just because the team managed to zap fear memories. Locating where the memories were stored in the first place is being hailed as a major accomplishment.
“This really then is a proof of principle that these are really the neurons that are involved in storing this kind of memory,” said Dr. Michael Salter, head of the program in neurosciences and mental health at Toronto’s Hospital for Sick Children, where the research team is based.
The study, published Thursday in the journal Science, was led by Sheena Josselyn and Paul Frankland, partners in research and in life. The couple just had a baby and were unavailable for interviews, though Josselyn — the senior author — described the work in an interview that was podcast by Science.
She and others were quick to say that it remains to be seen if the mice findings can be translated into therapies for people suffering from crippling fears provoked by traumatic memories or from post traumatic stress disorder.
“Whether it works for other types of memory … or whether it would work in another type of mammal — say a human — we don’t know,” Josselyn said in the Science podcast.
Josselyn and her team had earlier reported that neurons in the lateral amygdala that produce high levels of a protein called CREB seem to be activated when fears triggered by sounds are imprinted on the brains of mice. The amygdala is known to be involved in the processing and storage of emotion memory.
The work was done using a classic training technique in which a mouse in a chamber hears a sound followed by a weak shock that comes through the chamber floor. From then onward, every time the mouse hears the tone, it will assume a crouch position that mice in the wild use to try to hide from predators.
In this study, the scientists identified the neurons that were over-producing CREB when the trained mice heard the tone, and zapped only those neurons using a diphtheria toxin. They then exposed the treated mice to the tone. The mice did not react, suggesting their memory linking it to fear of the shock was erased.
PTSD treatment a possible goal
The scientist whose work in reconsolidating memory — a term which means in essence reworking a memory — inspired Eternal Sunshine of the Spotless Mind said Josselyn’s team has found “one of the Holy Grails” of memory work.
“The elegance in this one, which goes orders of magnitude beyond other studies, is that now they didn’t do something that was global to all neurons in the lateral nucleus,” said Karim Nader, a professor of neuroscience at McGill University in Montreal.
“They can kill only the neurons that they think express the memory. And it leaves all the other neurons intact.”
Nader said the work could eventually help scientists figure out how to assist people in overcoming pathological fears caused by the memory of a traumatic event.
But much remains to be done before that could happen. For instance, the technique Josselyn’s team used worked wonderfully in mice, but couldn’t be used in people.
“In humans, one wouldn’t want to kill these neurons. And certainly it’s not feasible to do it by this technology because you’re not going to inject diphtheria … viruses [into people],” said Salter, who is Josselyn’s department head but who was not involved in her work.
“So as a therapeutic strategy, this isn’t going to be it. But the idea is then to use this as a step forward and then to go on to come up with strategies that could then be used.”
Salter said it is conceivable that the storage system for fear-based memories that’s at work in a mouse brain is similar to the system by which fear memory is stored in human brains.
“Many of these biochemical pathways are conserved all the way from fruit flies up into humans,” he said. “So I think that’s the tack, is to try to find commonalities and take advantage of those commonalities.”
Salter said in building on this and other work, scientists may figure out a way to manipulate fear memories so that excessive fear is toned down, but the memory itself is not erased.
Are men too manly to seek help for their medical problems?
UBC researchers study effects of masculinity on men’s health choices
By Amy O’Brian, Vancouver Sun – March 13, 2009
It’s a well-known fact that men generally don’t like to admit weakness—that they don’t like going to the doctor or asking for help.
Such traits are commonly associated with the constructs of masculinity, which has led a group of researchers at the University of B.C. to examine men’s health within that context.
“We’re looking at men’s health in a new way, by trying to understand some of men’s health behaviour in relation to masculinity,” Joan Bottorff, a professor in UBC’s school of nursing, said Thursday in an interview.
“It provides a different way of looking at men’s health and therefore opens up some new avenues for promoting men’s health.”
Depression, heart health, smoking cessation and sexual health are four areas of research being examined at a forum this evening at Robson Square, as part of UBC’s Celebrate Research Week. The researchers all work at UBC’s school of nursing.
John Oliffe is investigating depression in men and the strategies men use to cope with it.
“The interesting piece around men’s depression is that men are diagnosed at half the rate of women,” Oliffe said. “But their suicide rate is four times that of women.”
Men tend to “self-manage” their depression with alcohol, drugs or violence, which is sometimes directed at their partner or spouse. Oliffe says many men are unwilling to take antidepressants, but there is an increasing willingness to talk about their depression.
“That’s new,” Oliffe says. “There seems to be an emerging interest, particularly among younger and middle-aged men, to be involved in talk therapy.
“We’re finding that there’s a real willingness to either talk with peers—other men who might be having issues—or professional counsellors.”
Bottorff has been studying smoking cessation among men, particularly those with infants or young children.
Part of the reason for the study is that 70 per cent of women who quit smoking while pregnant return to the bad habit within six months of giving birth. A key risk factor for those women is having a partner who smokes.
Bottorff says quitting cold turkey is one of the most popular smoking cessation methods among men, even though it has proven to be one of the most unsuccessful. Using a nicotine replacement such as the patch is proven to have a higher success rate, but Bottorff says men would rather focus on willpower and strength than relying on an “aid.”
Bottorff has no data regarding the most successful method of quitting, but says fathers who become heavily involved in caring for a baby are more likely to quit.
Other studies being pursued in the area of men’s health include an examination of how Punjabi men approach rehabilitation after having a heart attack, and another examining sexual health among men. Some of the studies are still recruiting subjects.
Background Tree Mortality Rates Increase in Old Forests
Lori Daniels, Ph.D., R.P.Bio.
Department of Geography, UBC-Vancouver
Tree death rates have more than doubled over the last few decades in old-growth forests of the western United States and southwestern British Columbia, and the most probable cause of the worrisome
trend is regional warming, according to a study published in Science on January 23, 2009.
Our study compares population changes in forests in southern British Columbia, Washington, Oregon, California, Idaho, Colorado and Arizona. For the last 15 to 50 years my colleagues and I have monitored 76 permanent plots that include more than 58,736 trees. During that time,11,095 trees died and tree mortality rates have more than doubled in recent decades.
Tree death is a natural part of old-growth forest dynamics. Each year we expect a small number of trees to die. But our long-term monitoring of many types of old forests shows that tree mortality has
been increasing, but the establishment and growth of replacement trees has not. As a result, the forests are losing trees faster than they are gaining them.
Mortality rates, the rate at which trees die, have increased from just under 1% to almost 2% per year. These numbers may seem small, but tree death rates are like interest on a bank account – the
effects compound over time. So, a doubling of death rates eventually could reduce average tree age in a forest by half, thus reducing average tree size.
The increase in dying trees has been pervasive. Tree death rates have increased across a wide variety of forest types, at all elevations, in trees of all sizes, and in pines, firs, hemlocks, and other genera.
Ultimately increased mortality rates could lead to substantial changes in western forests. As trees die, they change the composition and structure of the forest, which can have cascading effects, such
as altering habitat for wildlife species. Additionally, increasing tree mortality rates mean that western forests could become net sources of carbon dioxide to the atmosphere, further speeding up the pace of global warming.
Our study ruled out a number of possible sources of the increasing tree deaths, including air pollution, long-term effects of fire suppression, and forest dynamics associated with stand development such as self-thinning of even-aged stands. In contrast, increasing regional temperature was correlated with tree deaths.
Average temperature in western North America rose by over 1.0° C over the last few decades. While this change may sound modest, it was enough to reduce winter snowpack, cause earlier snowmelt, and lengthen the summer drought.
Changes in length of summer drought could be stressing trees, leading to higher death rates. Warmer temperatures also might favor insects and diseases that attack trees. For example the recent
outbreak of mountain pine beetle in British Columbia has already been linked to warming temperatures.
In some cases, increasing tree deaths could indicate forests vulnerable to sudden, extensive die-back, similar to forest die-back seen over the last few years in parts of the southwestern states, Colorado, and British Columbia. This is a major concern – the trend increased death rates indicate our forests are stressed and may be susceptible to bigger, more abrupt changes.
Complete findings appear in the article, Widespread increase of tree mortality rates in the western United States, by Phillip J. van Mantgem (USGS), Nathan L. Stephenson (USGS), John C. Byrne
(U.S. Forest Service), Lori D. Daniels (University of British Columbia), Jerry F. Franklin (University of Washington), Peter Z. Fulé (Northern Arizona University), Mark E. Harmon (Oregon State University), Andrew J. Larson (University of Washington), Jeremy M. Smith (University of Colorado), Alan H. Taylor (Pennsylvania State University), and Thomas T. Veblen (University of Colorado), published in Science (Volume 323: 521-524; DOI: 10.1126/science.1165000)
Association of Professional Biologists of British Columbia BIONews volume 19 number 1 pp 7-8
Wed Feb 01
