With the previous decades increase in ozone-depleting gases and now the more recent results of an increase in carbon dioxide, new research suggests that southern South America is likely to see more and more wildfires as climate conditions are negatively affected by human intervention.
Researchers from the University of Colorado at Boulder dated tree rings back to 1506 to track wildfire activity in the forests of Patagonia and tied increased wildfire activity to a positive phase of the Southern Annualar 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 the Southern Annualar Mode was in its positive phase there were fires in both the dry woodlands and the wetter rainforests in Patagonia.
“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 CU-Boulder Research Associate Andres Holz, lead study author.
“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.”
“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 co-author and CU-Boulder geography Professor Thomas 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.”
Holz and Veblen compared past wildfire records for the relatively dry region of northern Patagonia in Argentina and the temperate rainforest of Patagonia in Southern Chile and found that increased wildfires in both regions corresponded to a positive phase of SAM.
Fire suppression in the region of northern Patagonia is probably the reason the trend was less pronounced over the past 50 years. This same fire suppression, however, has caused the region to become denser and, subsequently, more prone to wildfire during hot and dry years, Holz said.
“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.”
Despite the fact that the Antarctic ozone hole is believed to have stopped growing and may in fact be in retreat, thanks in part to the ban on ozone-depleting gasses, a 2011 paper by researchers at the National Center for Atmospheric Research in Boulder suggest that any recovery will be cancelled out by the increase in atmospheric carbon dioxide levels.