MOUNTAIN pine beetle is known to eat into the bark of pine and kill them. But the bug causes more harm than is apparent. A study published in Nature Climate Change on October 28 states severe beetle infestations in Colorado watersheds of the Rocky Mountains in the US have considerably deteriorated the water quality of streams in the region that provide water to over 60 million people.
After the pines die and fall into streams and rivers, the wood and needles decay and release dead organic matter in water. When this organic matter reaches water treatment facilities, it reacts with chlorine and gives rise to several cancerous byproducts like trihalomethane. These chemicals can affect the nervous system, liver, kidneys, heart and the reproductive system.
Rise in beetle population is linked to warming, says Kristin Mikkelson of the Colorado School of Mines, who led the study. “Very low temperatures in winters always kept the population of pine beetles down. But even minimum winter temperatures in the past decades have been too high to kill enough of them,” she says. This, combined with droughts, which make trees weak and susceptible to infection, has contributed heavily to the recent large-scale pine tree die-off in North America, she adds. Werner Kurz, a senior scientist at Natural Resources Canada in British Columbia, Canada, cites one more reason. “Introduction of fire suppression has made pine forests, the sole host of pine beetle, grow older and larger. This supports the beetle’s survival,” he says.
For the study, the researchers collected water-quality data from nine water treatment plants in Colorado. These included five facilities which source water from sites highly infested with pine beetle and four facilities that get water from areas with very low infestation. The findings were alarming.
The trihalomethane concentrations in the water from treatment facilities in infested basins were on an average 353 per cent higher than the concentrations at facilities getting water from areas with low infestation. Significantly high level of organic matter was found in water from highly infested areas. Mikkelson says as rapid climate change continues to alter ecosystem dynamics across the globe, its impact on water quality also needs to be monitored along with water quantity.
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