Posts tagged National Science Foundation
Evidence of global climate in Southern Hemisphere
Aug 22nd
SOUTHERN SOUTH AMERICAN WILDFIRES
EXPECTED TO INCREASE, SAYS CU STUDY
A new University of Colorado Boulder study indicates a major climate oscillation in the Southern Hemisphere that is expected to intensify in the coming decades will likely cause increased wildfire activity in the southern half of South America.
The research team used tree rings dating to 1506 to track past wildfire activity in the forests of Patagonia tied to the Southern Annular Mode, or SAM, a climate oscillation that creates low atmospheric pressure in the Antarctic that is tied to warmer and drier conditions in southern South America. The tree rings showed that when SAM was in its positive phase, there were widespread fires in both dry woodlands and rainforests in Patagonia, a region that straddles Argentina and Chile, said CU-Boulder Research Associate Andres Holz, lead study author.
“Our study shows for about the past 250 years, the Southern Annular Mode has been the main driver in creating droughts and fires in two very different ecosystems in southern South America,” said Holz. “Climate models suggest an increase in SAM beginning in the 1960s due to greenhouse gas increases and Antarctic ozone depletion probably will cause this region to be drought-prone and fire-prone for at least the next 100 years.”
A paper on the subject by Holz and CU-Boulder geography Professor Thomas Veblen was published in Geophysical Research Letters.
Holz and Veblen compared past wildfire records for two ecologically distinct regions in Patagonia — the relatively dry region of southern Patagonia in Argentina and the temperate rainforest of Patagonia in northern Chile. While the tree ring historical record showed increased fires in both regions correlated with a positive SAM, the trend has been less pronounced in northern Patagonia in the past 50 years, likely because of fire-suppression efforts there, Holz said.
But the decades of fire suppression have caused the northern Patagonian woodlands to become denser and more prone towildfire during hot and dry years, Holz said.
“Even in areas of northern Patagonia where fire suppression previously had been effective, record surface areas of woodlands and forests have burned in recent years of extreme drought,” said Veblen. “And since this is in an area of rapid residential growth into wildland-urban interface areas, this climate-driven trend towards increasing fire risk is becoming a major problem for land managers and homeowners.”
The two CU-Boulder researchers studied reconstructions of tree rings going back more than 500 years from 432 trees at 42 sample sites in northern Argentina and southern Chile — the largest available data set of annual, readable tree ring records in the Southern Hemisphere. The tree rings, which indicate climate cycles and reveal the scars of old fires, showed that wildfires generally increased in both regions when SAM was in its strong, positive phase.
Although the Antarctic ozone hole stopped growing in about 2000 as a result of a ban on ozone-depleting gases and now appears to be slowly repairing itself, a 2011 paper by researchers at the National Center for Atmospheric Research in Boulder indicates ozone recovery and greenhouse gas influences essentially will cancel each other out, preventing SAM from returning to its pre-1960s levels.
“Before the Industrial Revolution, SAM intensified naturally at times to create drought situations in Patagonia,” Holz said. “But in the last 80 years or so, the natural variation has been overwhelmed by a bias toward a positive SAM phase because of ozone-depleting chemicals and greenhouse gases we have put in the atmosphere.”
The research effort was supported by the National Geographic Society, the National Science Foundation, the CU Beverly Sears Small Grants Program and the Council on Research and CreativeResearch of the CU Graduate School.
“As warming and drying trends continue, it is likely that wildfire activity will increase even in woodland areas where fire suppression has previously been effective,” Holz and Veblen wrote in Geophysical Research Letters.
NEW CU-BOULDER STUDY REVEALS BACTERIA FROM DOG FECES IN OUTDOOR AIR OF URBANIZED AREAS
Aug 18th
Bacteria from fecal material — in particular, dog fecal material — may constitute the dominant source of airborne bacteria in Cleveland’s and Detroit’s wintertime air, says a new University of Colorado Boulder study.
The CU-Boulder study showed that of the four Midwestern cities in the experiment, two cities had significant quantities of fecal bacteria in the atmosphere — with dog feces being the most likely source.
“We found unexpectedly high bacterial diversity in all of our samples, but to our surprise the airborne bacterial communities of Detroit and Cleveland most closely resembled those communities found in dog poop,” said lead author Robert Bowers, a graduate student in CU-Boulder’s ecology and evolutionary biology department and the CU-headquartered Cooperative Institute for Research in Environmental Sciences, or CIRES. “This suggests that dog poop may be a potential source of bacteria to the atmosphere at these locations.”
The study was published July 29 in Applied and Environmental Microbiology. Co-authors on the study included Noah Fierer, an assistant professor in CU-Boulder’s ecology and evolutionary biology department and a CIRES fellow; Rob Knight, an associate professor in CU-Boulder’s chemistry and biochemistry department; Amy Sullivan and Jeff Collett Jr. of Colorado State University; and Elizabeth Costello of the Stanford University School of Medicine.
Scientists already knew that bacteria exist in the atmosphere and that these bacteria can have detrimental effects on human health, triggering allergic asthma and seasonal allergies, Fierer said. But it is only in recent years that researchers have realized that there is an incredible diversity of bacteriaresiding in the air, he said.
“There is a real knowledge gap,” said Fierer. “We are just starting to realize this uncharted microbial diversity in the air — a place where you wouldn’t exactly expect microbes to be living.”
To gain further understanding of just what microbes are circulating in urban environments, the team analyzed the local atmosphere in the summer and winter at four locations in the Great Lakes region of the U.S. Three of the locations — Chicago, Cleveland and Detroit — are major cities with populations of greater than 2 million, and one location, Mayville, Wis., is a small town with a population of less than 6,000.
The team used nearly 100 air samples collected as part of a previous study conducted by Colorado State University. The CSU experiment investigated the impact of biomass burning and involved studying the impacts of residential wood burning and prescribed fires on airborne fine particle concentrations in the midwestern United States.
“What we’ve been looking at are the numbers and the types of bacteria in the atmosphere,” Fierer said. “We breathe in bacteria every minute we are outside, and some of these bugs may have potential health implications.”
The researchers analyzed the bacteria’s DNA in the collected air samples and compared the bacteria they found against a database of bacteria from known sources such as leaf surfaces, soil, and human, cow and dog feces. They discovered that the bacterial communities in the air were surprisingly diverse and also that, in two of the four locations, dog feces were a greater than expected source of bacteria in the atmosphere in the winter.
In the summer, airborne bacteria come from many sources including soil, dust, leafsurfaces, lakes and oceans, Bowers said. But in the winter, as leaves drop and snow covers the ground, the influence that these environments have as sources also goes down. It is during this season that the airborne communities appeared to be more influenced by dog feces than the other sources tested in the experiment, he said.
“As best as we can tell, dog feces are the only explanation for these results,” Fierer said. “But we do need to do more research.”
The team plans to investigate the bacterial communities in other cities and to build a continental-scale atlas of airborne bacterial communities, Fierer said. “We don’t know if the patterns we observed in those sites are unique to those cities,” he said. “Does San Francisco have the same bacteria as New York? Nobody knows as yet.”
Fierer believes it is important to pin down the types of bacteria in the air, how these bacteria vary by location and season, and where they are coming from.With this information, scientists can then investigate the possible impacts on human health, he said.
“We need much better information on what sources of bacteria we are breathing in every time we go outside,” Fierer said.
The study was funded by the CIRES Innovative Research Program, the U.S.
Environmental Protection Agency, the National Science Foundation, the Howard Hughes Medical Institute and the National Institutes of Health. The aerosol sample collection for this project was supported by the Lake Michigan Air Directors Consortium.