Wildfires have been raging in Patagonia, on the tip of South America, in both Argentina and Chile.
Summer has been blazing hot in the region, with the central part of Argentina reaching a record high of 113 degrees Fahrenheit in mid-January. On Jan. 12, Argentina’s federal government declared a one-year fire “emergency” because of the ongoing situation.
Though the native vegetation in much of the region consists of wet forest, major forest fires have become much more frequent in recent decades as the climate changes. Imported North American tree species, heat, drought, and changing weather patterns that produe dry thunderstorms are also altering the natural fire patterns.
“We are witnessing now very strong changes due to climate change,” says Thomas Kitzberger, a professor of ecology at the National University of Comahue in Bariloche, Argentina, not far from the recent forest fires.
“We are witnessing a 50-year-long trend in drying and in warming. We are experiencing hot spells; we are experiencing thunderstorms, which were not very common in this region in the past...and, of course, very large fires in recent times."
“We are witnessing a 50-year-long trend in drying and in warming,” he continues. “We are experiencing hot spells; we are experiencing thunderstorms, which were not very common in this region in the past; mortality of forests, even without fire — trees die off due to drought; and, of course, very large fires in recent times. So we are very concerned about those changes."
The southern temperate forests of the region consist of evergreen trees that are very different from those found in the North American coniferous forest, Kitzberger explains. Like in the US Pacific Northwest, theses forests are fed by rains that come in from the Pacific Ocean. This moisture also generates other forest types, like rainforest, shrublands, and the Patagonian Steppe, which is a grassland. But unlike in the northern hemisphere, most of these species are not well adapted to fire.
Until recently, this has not been a problem because fires occurred about every 300 to 500 years and were typically small.
When fires occur infrequently, a mature forest can withstand them because the trees are large. The trees that survive create a new generation of trees that can thrive until the next fire.
"[U]nder new climatic scenarios, the forest will burn more frequently if the ignition is there. And the ignition is there now because there are more people and there are more lightnings.”
“The problem is that under new climatic scenarios, the forest will burn more frequently if the ignition is there,” Kitzberger says. “And the ignition is there now because there are more people and there are more lightnings.”
Kitzberger and other scientists have detected this during the past 10 years. Since the 1980s and 1990s, the number of reported lightning-ignited fires has tripled compared to the period from the 1950s to the 1970s, a phenomenon that correlates with increased temperatures during the summers.
"We're having hotter summers, drier summers, and summers that are more prone to thunderstorms,” Kitzberger explains. “And these thunderstorms are related to a change in the circulation of the subtropical air masses that come from the Amazon and from Northern Argentina [and] Paraguay. And they are funneled in from the north to the plains of the Andes, as far south as Bariloche, and even farther south.”
In the past, Kitzberger says, this climatic pattern was uncommon because the region typically has a westerly wind circulation, which normally consists of very stable air and does not produce lightning. Storms driven by a northerly wind contain very unstable air that produces dry thunderstorms. These storms are dangerous in the region because they don't produce much rain, but they do produce lightning. If the lightning combines with drought, the probability of ignition is high.
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The problems have been made worse by a monoculture of pine trees that were planted in the region for timber decades ago. These plantations were promoted and heavily subsidized by the Argentine government in the 1970s and 1980s, Kitzberger says.
Landowners were given money to plant northern hemisphere pine trees, such as Ponderosa pine, Douglas fir and Lodgepole pine, all of which are highly flammable species. Many of these plantations were later abandoned.
“There was not really a market for this wood,” Kitzberger says. “The wood was not very high quality. So the plantations were abandoned because the money was already cashed in. The government paid for the seedlings, they didn't pay for the mature trees.”
Once the plantations were established, they were not taken care of or thinned, so they became loaded with dry fuels. This invasion of conifer trees into native ecosystems created what scientists call “novel ecosystems” — combinations of native trees with non-native conifer trees. The non-native trees establish beneath the canopy of the native trees.
“The problem is, when a fire sweeps through that invaded native ecosystem, the dominant tree after the fire sweeps through the forest will be the exotic [non-native] conifer."
“The problem is, when a fire sweeps through that invaded native ecosystem, the dominant tree after the fire sweeps through the forest will be the exotic [non-native] conifer,” Kitzberger explains.
Fire policies from North America are being applied to Patagonia, which Kitzberger says is a mistake. In North America, mature forests tend to be more flammable, which has led to the practice of prescribed burning to help reduce the potential for intense wildfires.
“Here in Patagonia, it's absolutely the reverse,” he explains. “When you burn a forest, you create a shrubland, and the shrubland is more flammable than the forest. So prescribed burning would create the opposite effect here in our forests than in a coniferous forest.”
Patagonia is likely experiencing a new normal, Kitzberger believes.
Most global climate change models predict the region can expect at least a 20% to 30% reduction in rainfall and a temperature increase of 2 to 3 degrees Celsius under probable greenhouse gas emission scenarios. Fire frequency could increase “two- to three-fold during the mid-21st century and six- to eight-fold during the late 21st century, which would be really disastrous for our ecosystems,” he says.
“We really have to assume that the conditions of the future are going to be different,” Kitzberger concludes. “We cannot have the romantic idea of going back to our 19th century landscape because it's a romantic view, which is not going to be very resilient to the future conditions.”
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