Effects of Pine Beetle Epidemic on Water Quality in Boulder County, CO

Abstract

Bark Beetle infestation in areas of the Rocky Mountain Range has had a large impact on its surrounding ecosystem, especially as the warmer climate has increased the reproduction cycle of the beetles. Subsequent tree die-out events have been shown to increase water runoff and the concentration of nitrates in soil. This study provides evidence that insect damage in Boulder County, CO has resulted in a significant increase in nitrate levels in localized areas of streams between 5 and 20 years after the initial beetle infestation. Over twelve observed streams, I found that water samples within beetle infestation sites on average had 32% higher nitrates than water samples upstream of the beetle infestation. Total dissolved solids (TDS) showed a strong correlation with nitrate levels. I found no significant difference in downstream nitrate change when stratified by dominant sapling genus, but I found that when grouped by dominant adult, nitrates were higher in aspen-dominated areas than in spruce-dominated areas. Levels of nitrates in beetle sites of 20 years were significantly higher than those in 15-year sites, but no further trend was seen in nitrate levels by latent period. Lastly, I found a significant increase in nitrate levels at sites with greater percentages of dead trees. Elevation of nitrates in stream water is a public health concern, as toxins from high-concentration streams can cause harm to humans and other animals. Further research would be required to determine whether nitrate values remain elevated downstream, beyond beetle infestation zones. Studies on impacts from bark beetle damage are ever more critical as climate change makes these infestations more prevalent in mountainous areas like Boulder, CO.