An international team of scientists have identified a new species now called “the mesoamerican pine beetle” that is causing “catastrophic” damage to forests across Central America.
The new species, Dendroctonus mesoamericanus, works in concert with its cousin, the southern pine beetle, Dendroctonus Frontalis. Both are responsible for damage to pines, according to the United States Department of Agriculture.
Bark beetles of the genus Dendroctonus rank high among the most destructive conifer pests. The mountain pine beetle has destroyed forests across British Columbia and is now moving into Alberta.
The USDA says attacks “attributed to the southern pine beetle has led to declines in pine forests and multimillion dollar losses in timber, recreation, and other ecosystem services,” in Mexico, Belize and other countries in Central America.
As far back as 2002, scientists suspected, but could not confirm, that the problems in Central America were caused by two different pine beetles. From early 2000 to 2002, 25,000 hectares of mature pine stands in the Mountain Pine Ridge Forest Reserve of Belize were devastated by an outbreak of what was initially identified as the southern pine beetle. At the time the scientists investigating the outbreak suspected the trees were also infested by a second insect that they then called the “caribbean pine beetle.” However, there was insufficient evidence at the time to warrant scientific publication.
Between 2006 and 2010, Brian Sullivan, an entomologist with the USDA, and his colleagues, conducted studies on the pheromone and body wax chemistry of the beetle. Those studies provided clear biological evidence that it was a species new to science. Extension and forest health education programs in the Central American region have already begun to include information on the mesoamerican pine beetle.
“We found in research with our cooperators in Mexico and Norway that insects previously identified as southern pine beetles are actually two different species — southern pine beetle and the newly identified mesoamerican pine beetle,” said Sullivan. “The new species is nearly indistinguishable from the southern pine beetle. The two species appear to work in cooperation to kill trees, and outbreaks by both may be more persistent and destructive than those by southern pine beetle alone.”
Southern and mesoamerican pine beetles do differ in several respects. The mesoamerican adults tend to be somewhat larger than the southern pine beetle, and the holes where they enter the tree’s bark exude more resin, producing bigger “pitch tubes.”
Field observations suggest that the new species attacks trees shortly after southern pine beetle, colonizing the lower trunk and branches. The mesoamerican pine beetle also has a distinct pheromone chemistry and does not respond to traps baited with southern pine beetle lures.
Researchers have found mesoamerican pine beetles attacking eight species of native Central American pines and have collected the insect from Belize, southern Mexico, in Oaxaca, and Chiapas states, in Guatemala, El Salvador, Honduras, and Nicaragua. In these countries, the species has been collected at elevations from 311 to 2600 metres.
“A thorough understanding of this species complex – the southern and mesoamerican pine beetle acting in concert — may prove critical for developing integrated pest management strategies for the Central American region,” said Sullivan. “This discovery also brings to light a potential exotic threat to the U.S. that was not previously known to exist.”
Initial observations may indicate that the mesoamerican pine beetle is not as aggressive as the southern pine beetle, but may take advantage of trees infested by the southern pine beetle, making things worse.
Authors of the description paper in Annals of the Entomological Society of America include Dr. Brian Sullivan, research entomologist with the Forest Service Southern Research Station, Francisco Armendariz-Toledano, graduate student with the Instituto Politecnico Nacional (IPN) in Mexico City; Dr. Gerardo Zuniga of IPN, Dr. Lawrence Kirkendall of the University of Bergen, Norway, and Alicia Nino, graduate student at El Colegio de la Frontera Sur (ECOSUR), Chiapas, Mexico.
A new study, based at the University of Alberta, released this week, indicates that natural selection may be making the mountain pine beetle more tolerant of colder temperatures and that the beetle may be evolving the ability to fly longer distances.
A second study, from the Colorado School of Mines, also released this week, is tracking how the extent of pine beetle infected or killed trees in forests is changing ground water and stream flows.
The mountain pine beetle infestation has wreaked havoc in North America, across forests from the American Southwest to British Columbia and Alberta. Millions of hectares of forest have been lost, with severe economic and ecological impacts from a beetle outbreak ten times larger than previous ones.
Dust from beetle killed wood is believed partially responsible for the explosions at the Lakeland Mill in Prince George and the Babine Forest Products mill in Burns Lake. The explosion in early 2012 at the Babine Forest Products mill killed two workers and injured another twenty. The Lakeland Mill explosion killed two workers and injured twenty four others.
As part of the fight to contain the mountain pine beetle, scientists recently sequenced the pine beetle genome.
Using that genome, Jasmine Janes and colleagues at the University of Alberta, with assistance from the University of British Columbia and the University of Northern British Columbia, used genetics to track how the pine beetle was able to expand its range so rapidly. The study was published in Molecular Biology and Evolution.
Studied at molecular level
While teams of researchers have tracked the path of the pine beetle across BC on the ground, how the beetle spread so easily “is only beginning to be understood at the molecular level,” the study says.
Pine beetles were collected from 27 sites in Alberta and British Columbia. The University of Alberta scientists were especially interested in how the pine beetle was able to jump across the Rockies, something that earlier researchers believed would not happen.
By looking at the genetic markers, the team concluded that the pine beetle may have been able to spread by adjusting its cellular and metabolic functions to better withstand cooler climates and facilitate a larger geographic dispersal area.
In an e-mail to Northwest Coast Energy News, Janes said the research looked at genomic signatures to find out how the beetle had been able to spread into Alberta – where did it come from, what route did it take and how did it overcome the physical and climatic barriers that we had always assumed?
The research discovered that there are two genetically different populations of pine beetles, one from the south of British Columbia and Alberta and one in the north. Another group of pine beetles, found near Valemount, “were harder to classify as being from either north or south genetically. The beetles in this area were showing higher genetic diversity.”
The pine beetle has always been around and killed older trees (called “low quality hosts”), helping to renew the ecosystem. There were also larger five-year infestations that occurred on a 20 to 40 year cycle. The current pine beetle “epidemic” in BC has gone on now for more than 20 years, with the pine beetle “observed in previously unrecorded numbers” over a much wider area
It is generally believed that climate change has help the pine beetle survive milder winters.
The study notes:
Successful establishment of mountain pine beetle on pure jack pine in northern Alberta has raised concerns that the mountain pine beetle will continue to expand its range into the vast boreal forest of jack pine that extends across North America from the Northwest Territories to the Atlantic Coast.
The teams concludes that one group of the beetles originated in southwestern BC perhaps from Whistler or Manning Park. Then the beetles spread north up the west coast of BC toward Houston “with rapid population size increases in central and northern BC and then dispersed long distances with prevailing winds toward the east and Alberta.”
Some of the beetles from southwestern BC appear to have taken a different route, moving more slowly eastward in the south of BC toward Crowsnest Pass area and then moving northward along the base of the Rockies, Janes said, adding. “Our research suggests that these two routes have then met in the middle again, around Valemount and that is why we see the genetic patterns across the landscape that we observed.”
The second part of the research was answering the question of how the beetles were able to do this. How could they withstand the colder temperatures to spread further north and east?
To answer the scientists used the same genetic markers (single nucleotide polymorphisms) to conduct “selective sweeps” of the beetle genome. The sweeps look for unusual genetic markers that could indicate the beetles are under “selective pressure.”
The study looked at specific functions in the beetle: the genes that govern “actin filaments” that “control muscle contractions like shivering and moving wings”; “the synthesis of cholesterol that provides energy for metabolic activities” and transport of ions across cell membranes.
Normally, female pine beetles can only fly short distances to find a new host tree to lay eggs. They can travel longer distances if they are up in the tree canopy and are then carried by the wind. Stronger pine beetles that can fly longer distances show the threat is likely evolving.
The study concludes that Canadian Mountain Pine Beetle range expansion:
may continue as populations are currently exhibiting signals of selection. These signals suggest ongoing adaptation of metabolic and cellular processes that could potentially allow them to withstand colder temperatures, shift developmental timing and facilitate longer dispersal flights.
Janes said further research is required to fully validate and understand these signatures of selection, but it does suggest that the beetle is adapting and that is why it “may have been able to breach the Rocky Mountains”
Water and trees
In Colorado alone, the mountain pine beetle has caused the deaths of more than 3.4 million acres of pine trees. The new research findings show the consequences of an obvious observation: Dead trees don’t drink water
The Colorado study asked how all those dead trees are changing stream flow and water quality?
“The unprecedented tree deaths caused by these beetles provided a new approach to estimating the interaction of trees with the water cycle in mountain headwaters like those of the Colorado and Platte Rivers,” said Reed Maxwell a hydrologist at the Colorado School of Mines.
Maxwell and colleagues have published results of their study of beetle effects on stream flows in this week’s issue of the journal Nature Climate Change.
As the trees die, they stop taking up water from the soil, known as transpiration. Transpiration is the process of water movement through a plant and its evaporation from leaves, stems and flowers.
The “unused” water then becomes part of the local groundwater and leads to increased water flows in nearby streams.
“Large-scale tree death due to pine beetles has many negative effects,” says Tom Torgersen of the US National Science Foundation’s Directorate for Geosciences and program director for the NSF’s Water, Sustainability and Climate program.
“This loss of trees increases groundwater flow and water availability, seemingly a positive,” Torgersen says.
“The total effect, however, of the extensive tree death and increased water flow has to be evaluated for how much of an increase, when does such an increase occur, and what’s the water quality of the resulting flow?”
Under normal circumstances, green trees use shallow groundwater in late summer for transpiration.
Red- and gray-phase trees–those affected by beetle infestations–stop transpiring, leading to higher water tables and greater water availability for groundwater flow to streams.
The Colorado study shows that the fraction of late-summer groundwater flows from affected watersheds is about 30 per cent higher after beetles have infested an area, compared with watersheds with less severe beetle attacks.
“Water budget analysis confirms that transpiration loss resulting from beetle kill can account for the increase in groundwater contributions to streams,” write Maxwell and scientists Lindsay Bearup and John McCray of the Colorado School of Mines, and David Clow of the U.S. Geological Survey, in their paper.
Dead trees create changes in water quality
“Using ‘fingerprints’ of different water sources, defined by the sources’ water chemistry, we found that a higher fraction of late-summer stream flow in affected watersheds comes from groundwater rather than surface flows,” says Bearup.
“Increases in stream flow and groundwater levels are very hard to detect because of fluctuations from changes in climate and in topography. Our approach using water chemistry allows us to ‘dissect’ the water in streams and better understand its source.”
With millions of dead trees, adds Maxwell, “we asked: What’s the potential effect if the trees stop using water? Our findings not only identify this change, but quantify how much water trees use.”
An important implication of the research, Bearup says, is that the change can alter water quality.
The new results, she says, help explain earlier work by Colorado School of Mines scientists. “That research found an unexpected spike in carcinogenic disinfection by-products in late summer in water treatment plants.”
Where were those water treatment plants located? In bark beetle-infested watersheds.
The TRIA project (a collaboration of researchers at the University of Alberta, University of British Columbia, University of Montreal, University of Northern British Columbia). The TRIA project investigates the physiology, genetics and ecology of all three players in the mountain pine beetle system – the pines (lodgepole and jack pine, and their hybrids), the beetle and the fungus (several types).
The Colorado study is funded by the National Science Foundation’s (NSF) Water, Sustainability and Climate (WSC) Program. WSC is part of NSF’s Science, Engineering and Education for Sustainability initiative.
With temperatures climbing from climate change, the mountain pine beetle is now moving to higher elevations on mountain slopes, and is a “rising threat” to the whitebark pine, according to a University of Wisconsin-Madison study published today, Dec. 31, 2012, in the Proceedings of the National Academy of Sciences.
The whitebark pine is found mainly in the Rocky Mountains and Coast Range of British Columbia and into the northern United States.
In the US, there there have been a number of studies of pine beetle infestation of the whitebark pine. In 2011, the Seattle Timesreported
A study in the mid-2000s showed whitebark trees had declined by 41 percent in the Western Cascades. Tree declines throughout Washington and Oregon hovered around 35 percent. In the coastal range and the Olympics, blister rust infection ranged from 4 to 49 percent. Nearly 80 per cent of the whitebark in Mount Rainier National Park are infected. Whitebark deaths in North Cascades National Park doubled in the last five years.
The Seattle Times also quoted the U.S. Fish and Wildlife Service reporting in 2007 that beetles killed whitebark pine trees across half a million acres in the US West — the most, at the time, since record-keeping began. Two years later, beetles killed trees on 800,000 acres.
Ken Raffa, a University of Wisconsin -Madison professor of entomology and a senior author of the new report says.”Warming temperatures have allowed tree-killing beetles to thrive in areas that were historically too cold for them most years. The tree species at these high elevations never evolved strong defenses.”
A warming world has not only made it easier for the mountain pine beetle to invade new and defenseless ecosystems, the scientists say, but also to better withstand winter weather that is milder and erupt in large outbreaks capable of killing entire stands of trees, no matter their composition.
“A subject of much concern in the scientific community is the potential for cascading effects of whitebark pine loss on mountain ecosystems,” says Phil Townsend, a Univeristy of Wisconsin-Madison professor of forest ecology and a senior author of the study.
The mountain pine beetle’s historic host is the lodgepole pine, and it was widespread lower elevations until the pine beetle infestation began to spread in the late 1990s. The pine beetle which are about the size of a grain of rice, played a key role in regulating the health of a forest by attacking old or weakened trees and fostering the development of a younger forest after the older trees died or were destroyed by fire.
However, recent years have been characterized by unusually hot and dry summers and mild winters, which have allowed insect populations to boom. This has led to an infestation of mountain pine beetle described by the scientists as “possibly the most significant insect blight ever seen in North America.”
Over most of the Interior, extreme winter weather (colder than minus 35 Celsius for at least several days or even weeks) historically killed most of the pine beetle population, limiting the duration of, and damage from, periodic epidemics. Such a wide-spread weather event has not occurred in the B.C. Interior since the winter of 1995/96.
The lodgepole pine co-evolved with the bark beetle, ad so it evolved chemical countermeasures, volatile compounds toxic to the beetle and other agents that disrupt the pine bark beetle’s chemical communication system.
According to the Wisconsin study, despite that robust chemical defense system, the lodgepole pine is still the preferred menu item for the mountain pine beetle, suggesting that the beetle has not yet adjusted its host preference to whitebark pine. “Nevertheless, at elevations consisting of pure whitebark pine, the mountain pine beetle readily attacks it,” says Townsend.
The good news, he adds, is that in mixed stands, the beetle’s strongest attraction is to the lodgepole pine, suggesting that, at least in the short term, whitebark pine may persist in those environments.
However, the 2007 US study quoted by the Seattle Times also warned that unlike lodgepole, whitebark pines produce few seed cones and do so late in life, so they “aren’t set up to survive massive slaughter.”
The new study, conducted in the Greater Yellowstone Ecosystem, also showed that the insects that prey on or compete with the mountain pine beetle are staying in their preferred lodgepole pine habitat. That, says Townsend, is a concern because the tree-killing bark beetles “will encounter fewer of these enemies in fragile, high-elevation stands.”
Whitebark pine trees are an important food source for wildlife, including black and grizzly bears, and birds such as the Clark’s nutcracker named after the famed explorer and which is essential to whitebark pine forest ecology as the bird’s seed caches help regenerate the forests.
(According to Wikipedia Clark’s Nutcrackers each cache about 30,000 to 100,000 each year in small, widely scattered caches usually under 2 to 3 centimetres of soil or gravelly substrate. Nutcrackers retrieve these seed caches during times of food scarcity and to feed their young. Cache sites selected by nutcrackers are often favorable for germination of seeds and survival of seedlings. Those caches not retrieved by time snow melts contribute to forest regeneration. Consequently,Whitebark Pine often grows in clumps of several trees, originating from a single cache of 2–15 or more seeds. Douglas Squirrels cut down and store Whitebark Pine cones in their middens. Grizzly Bears and Black Bears often raid squirrel middens for Whitebark Pine seeds, an important pre-hibernation food. Squirrels, Northern Flickers, and Mountain Bluebirds often nest in Whitebark Pines, and elk and Blue Grouse use Whitebark Pine communities as summer habitat. )
The BC government report says the pine beetle epidemic has now killed an estimated 710 million cubic metres of commercially valuable pine timber, 53 per cent of all such pine in the province. The rate of damage has been slowing for several years, but is projected to grow to 58 per cent by 2017 (to 767 million cubic metres).
Both the provincial and federal governments have spent hundreds of millions of dollars on the mountain pine beetle epidemic, beetle killed pine forest is more vulnerable to forest fires, and it is possible that the drier wood from beetle killed wood is responsible for the explosions at mills in Burns Lake and Prince George.
The BC government report says
B.C. has been battling the mountain pine beetle epidemic since the year 2000. From 2001 through 2004, the focus was on limiting the spread of the infestation and harvesting infested and susceptible pine stands. Not content to wait for frosts and winter cold spells that normally control the beetle, the Province took other steps to control the beetle’s spread. However the infestation continued to spread dramatically to 2007.
Throughout last decade, government and industry concentrated on salvage harvesting, to recover maximum economic value, and the reforestation of the dead stands. The provincial and federal governments invested hundreds of millions of dollars in mitigating the infestation’s impacts, in developing new markets for beetle-killed lumber, and in creating economic strategies for the future.
At the same time, the forest industry invested in adapting its harvest and milling technologies to the ever-changing forest resource, using the knowledge and experience gained from a significant, but much smaller, beetle infestation that hit the Cariboo-Chilcotin in the mid-1980s.
These actions have placed the industry, government and communities in the best position to address the next phase of the epidemic, as harvest and milling activities inevitably start declining.