USA At 1pm on 26 June 2011 a tree fell onto a power line in the Santa Fe National Forest in New Mexico, starting one of the largest wildfires the state has ever seen. The flames swept across 16,000 acres of land, burning nearly half of the vegetation in the watershed and threatening the town of Los Alamos and the Los Alamos National Laboratory. By 3 August the fire was contained, but the impact of this massive burn continued to be felt long afterwards. In particular the region was plagued by flash floods in subsequent years, as bare soils failed to absorb heavy rains.
This relationship between wildfire and streamflow is well known. What isn’t clear is whether there are also wider regional effects on water supplies. In order to find out, Michael Wine and Daniel Cadol from the New Mexico Institute of Mining and Technology, US, analyzed the impact of wildfires on three New Mexico watersheds Jemez (1223 sq. km), Mogollon (191 sq. km) and Gila (4807 sq. km). Using satellite data and United States Geological Survey records going back to 1982, the researchers studied the spatial patterns of burning from more than 100 wildfires. By comparing this with stream gauge data they discovered the effect that these various wildfires had on water flow.
After controlling for climatic and snowpack variability, Wine and Cadol showed that annual streamflow increased by as much as one fifth in the Gila watershed in the three to five years following any major wildfire. “Soils under evergreen trees are often resistant to water, and if the fire has removed the soil organic horizon then high-intensity precipitation may run-off instead of infiltrating,” said Wine. In addition, the reduction in vegetation reduces the amount of transpiration, so water that would have been stored in trees ends up on the ground instead.
Increases in streamflow were also seen in the Mogollon watershed, where more than 90% of the watershed was burned during one fire, but no significant increases in water discharge were observed following sizeable wildfires in the Jemez watershed.
Wine and Cadol believe that this difference is due to the wildfire regimes in the regions, with the wildfires in Jemez tending to be smaller they never exceeded 20% of the watershed area. “It seems that the wildfire burn area has to exceed a certain threshold for the disturbance to cause a measurable impact on water yields,” said Wine, who published the findings in Environmental Research Letters (ERL).
The results show that when wildfires occur over a large enough area they have far-reaching consequences for regional water supplies, increasing the risk of floods, mudslides and rock-flows over a large area. There is also evidence that wildfire burn scars can influence local weather, with the decreased albedo from the darkened soil encouraging convection and the formation of thunderstorms.
Understanding how wildfires and streamflow interact could help to minimize the risks of flash flooding in the future. Better wildfire management of forested areas, such as allowing small controlled burns, could help to prevent the very large burns associated with increased streamflow. And if a large burn does occur, local land-managers can ensure that adequate preparations are made to protect people and property from potential flash-floods.
Government has urged Malawi Defence Force (MDF) soldiers who are deployed to guard Viphya Plantation against destruction to be vigilant by dealing with the perpetrators accordingly.
Msaka (left) walking in the plantantion
Minister of Mines, Energy and Natural Resources, Bright Msaka, made the statement Tuesday after touring the plantation, especially areas under the jurisdiction of Total Land Care and Raiply Malawi Limited.
Incidences of fire destroying numerous hectares of trees every year have been a never-ending song for the Viphya Plantation for over a decade now. The plantation is shared by two districts of Mzimba andNkhata Bay.
However, the issue has raged on in spite of efforts by government and its stakeholders to plant trees and guard them against destruction. Reports have indicated that more often, the fires that destroy the plantation are deliberately set rather than accidental.
The minister said government is aware that some disgruntled workers and individuals whose licences were cancelled are the ones setting fires in the plantation.
People need to know that this is a national asset, so if the department of forestry has denied somebody a licence for the reasons best known by the department, they are supposed to understand instead of setting fires, he said.
To mitigate the challenge, Msaka said government deployed MDF soldiers in protected forests across the country as a way of scaring people from destroying the plantations.
In spite of the effort, some people are still setting parts of the Viphya Forest on fire, regardless of the size of trees.
We have directed the Malawi Defence Force solders to deal with anyone setting bush fires and operating in the forest without licences and that the law will take its course [against them], he warned.
However, Msaka commended Raiply Malawi Limited and Total Land Care for utilizing the forest sustainably and adding value to the trees from the forest.
In the past, we have been cutting trees or sawing and selling them abroad at a very cheap price. We behaved like a prodigal son who squandered all what his father gave him.
We need to be very careful and be proud of what we inherited so that we can benefit from it and pass on those benefits to the next generation, advised the minister.
Earlier, Chief Executive Officer of Raiply Malawi Limited, Thomas Oomen, cited bush fires and encroachment as major challenges facing his company.
This year alone, we have lost about 526 hectares [of trees] to bush fires, unfortunately, most of these trees are below 15 years old but they are supposed to be harvested at the age of 25. This is dooming our future, said Oomen.
Chikangawa Forest consists of seven plantations comprising 53,000 hectares.
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