ason, which ultimately results in more area burned per year, and increased atmospheric particulate matter and smoke (Norby et al. 2010; Jenkins et al. 2014; Jolly et al. 2015). Wildfire smoke is and will be most common in western Montana, primarily because wildfires in forested areas produce large amounts of smoke (Westerling et al. 2006; IDDEQ 2013) (Figure 3-7).
In Montana, Department of Environmental Quality reports show that the number of communities or counties whose air quality rated as moderate, unhealthy, very unhealthy, or hazardous generally increased from 2010-2017 (Figure 3-8), as a result of increased acres burned by wildfires. However, these trends were followed by declining smoke in the below-average fire seasons of 2018 and 2019, but on track in 2020 to be similar to or exceed 2017. The number of smoke events in each health category shows similar trends, with western Montana valleys receiving the most unhealthy smoke days followed by the southeastern region of Montana. In 2017, the most recent year with regionally extensive wildfire activity, Seeley Lake, Lolo, Superior, and Frenchtown all had ten or more days where air quality was rated unhealthy, very unhealthy, or hazardous, with Seeley Lake experiencing 38 days with unhealthy and worse smoke conditions (see Section 2, plus sidebar in Section 4 titled The 2017 Seeley Lake Fires and Lung Function). Assuming that projected increases in extreme fire danger result in increased wildfire activity, Montana could expect an increase in summers exceeding moderate air quality standards, with more communities affected, especially in western Montana.
Increased fire danger for Montana in coming decades will likely result in decreased air quality in years with widespread wildfire activity, like 2017. Such years will be interspersed with years having average or below-average fire activity. Communities can adopt a suite of actions to mitigate adverse effects on citizens from poor air quality (McWethy et al. 2019; also, such actions are described in Section 5).
Climate change is affecting Montana’s water quantity and quality (Whitlock et al. 2017; MTDEQ 2019), each of which may, in turn, impact human health. For example, spring floods, which are expected to increase because of earlier snowmelt or extreme precipitation events (see Section 2), affect people’s health in a variety of ways. Immediate impacts include injury, hypothermia, death from drowning, exposure to toxic substances and pathogens released by flood waters, and exacerbation of underlying conditions such as cardiovascular or pulmonary disease (due the flood itself or cleaning up afterwards). Later complications include respiratory and skin infections, vector-borne illnesses, and mental health conditions (Du et al. 2010; Ryan et al. 2015; Paterson et al. 2018).
Floods also increase the risk of mold formation in homes (Bell et al. 2017), an environmental stressor that can impact anyone but particularly American Indian/Alaska Native children (Barros et al. 2018). Even in the absence of flooding, elevated rates of gastrointestinal disease have been associated with precipitation events (Carlton et al. 2016; Levy et al. 2016), as well as with dry conditions (Alexander et al. 2013; Friedrich 2013; Fouladkhah et al. 2019), though the latter association is weaker.
Water quality issues resulting from climate change may also come about because of changes to precipitation runoff, land use, and the way agricultural lands are managed (MTDEQ undated). Changes to the timing and amount of runoff can impact stream turbidity and sediment deposition, plus non-point pollution runoff and subsequent increased stream concentrations of undesirable compounds. Late season droughts may result in higher concentrations of pollutants—including fertilizers and pesticides—in warmer waters, potentially leading to decreased levels of dissolved oxygen and/or increased algal blooms.
Harmful algal blooms, often caused by cyanobacteria, are special cause for concern. Cyanobacteria have increased across the US from under 100 incidents in 2013 to o