Anthropogenic Stressors
Ground-level Ozone
Ground-level ozone pollution is an anthropogenic stressor for all three areas within the Shasta National Forest (Figure 1). Shasta county, containing Lake Shasta and a majority of Shasta National Forest, received an Ozone rating of F from the American Lung Association (2020), with 28 days over 71ppb Ozone and 2 days over 86ppb ground-level ozone concentration in 2020 (American Lung Association 2020; Sandhou 2018). Siskiyou county, which contains Mount Shasta, received an Ozone rating of C from the American Lung Association (2020), with 4 days over 71ppb ground-level ozone concentration in 2020 (American Lung Association 2020; Sandhou 2018).
Figure 1. Days per year that ground-level ozone exceeded 70ppb from 2010 to 2014 worldwide. Source.
Ground-level ozone is a harmful pollutant created by chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs), two other anthropogenic pollutants (Environmental Protection Agency (EPA) 2021a). The chemical reaction between NOx and VOCs is heat and light dependent, meaning it is more likely to accumulate during hot days in urban areas (EPA 2021a). However, ground-level ozone can be easily transported by wind, often blowing into rural areas from urban areas (EPA 2021a; Lin et al 2014). Since it is so easily transported by wind currents, ground-level ozone and greenhouse gasses emitted by China’s industries blow across the Pacific and into California (Lin et al 2014).
Ozone damages vegetation by preventing leaves from opening their stomata, interfering with photosynthesis by reducing carbon dioxide intake and oxygen release (Iowa Department of Natural Resources (Iowa DNR) 2021). This interference with photosynthesis reduces vegetation growth and makes plants more susceptible to disease, pests, and environmental stressors (Iowa DNR 2021; EPA 2021b). In the Mount Shasta region, Loblolly Pine (Pinus contorta) is the most vulnerable to ground-level ozone because it is found at lower elevations where ozone can accumulate and is listed as an ozone sensitive species (Anderson 2003; U.S. National Park Service (U.S. NPS) 2019). Of the trees found in the forest itself, Ponderosa Pine (Pinus ponderosa) is the most vulnerable to ground-level ozone due to its abundance and being listed as an ozone sensitive species (U.S. NPS 2019; EPA 2021b). In Lake Shasta, invasive Hydrilla (Hydrilla vericillata) is most vulnerable to ground-level ozone because it’s above water flowers can be directly exposed to ozone (Stop Aquatic Hitchhikers! 2017b).
 |
| Figure 1. Days per year that ground-level ozone exceeded 70ppb from 2010 to 2014 worldwide. Source. |
Ozone damages vegetation by preventing leaves from opening their stomata, interfering with photosynthesis by reducing carbon dioxide intake and oxygen release (Iowa Department of Natural Resources (Iowa DNR) 2021). This interference with photosynthesis reduces vegetation growth and makes plants more susceptible to disease, pests, and environmental stressors (Iowa DNR 2021; EPA 2021b). In the Mount Shasta region, Loblolly Pine (Pinus contorta) is the most vulnerable to ground-level ozone because it is found at lower elevations where ozone can accumulate and is listed as an ozone sensitive species (Anderson 2003; U.S. National Park Service (U.S. NPS) 2019). Of the trees found in the forest itself, Ponderosa Pine (Pinus ponderosa) is the most vulnerable to ground-level ozone due to its abundance and being listed as an ozone sensitive species (U.S. NPS 2019; EPA 2021b). In Lake Shasta, invasive Hydrilla (Hydrilla vericillata) is most vulnerable to ground-level ozone because it’s above water flowers can be directly exposed to ozone (Stop Aquatic Hitchhikers! 2017b).
Climate Change
Temperature
The historical maximum daily average temperature (MDAT) for the Shasta National Forest varies by location, with Mount Shasta at ~40℉, the forest itself at ~65℉, and Lake Shasta at roughly 70℉-75℉ (Figure 1, U.S. Global Change Research Program 2021). Under the RCP 8.5 scenario, or a high emission climate change scenario assuming no changes made to reduce emissions, Shasta National Forest as a whole is predicted to experience a noticeable increase in MDAT (Hausfather 2019; Figure 2, U.S. Global Change Research Program 2021). Mount Shasta’s MDAT is predicted to increase to ~50℉, the forest itself could increase anywhere from ~70℉ to ~80℉, and Lake Shasta’s MDAT could increase to ~85℉ (U.S. Global Change Research Program 2021).
 |
| Figure 2. Historical (1961-1990 average) maximum daily average temperature (MDAT) for Northern California. Source. |
 |
| Figure 3. RCP 8.5 climate change scenario maximum daily average temperature (MDAT) for the 2090s in Northern California. Source. |
Climate change will increase the frequency and severity of wildfires in the Shasta National Forest (Borunda 2020). Warmer air temperatures reduce soil moisture, increase drought events, and dry out more fuel for wildfires, all increasing the likelihood of wildfires occurring and their potential severity from the increased amount of dried fuels (Figure 3, Borunda 2020). Additionally, the ~10℉ temperature increase in the Mount Shasta region could reduce snowpack, resulting in less water from snow melt that contributes to the Sacramento and McCloud rivers that feed into Lake Shasta (Environmental Protection Agency (EPA) 2020; NRCS 2021).
 |
| Figure 4. 2020 wildfire potential for the western United States. Source. |
Precipitation
Total annual precipitation across Shasta National Forest is expected to increase 1% to 8% (U.S. Global Change Research Program 2021). This increase in precipitation, accompanied by earlier / quicker snowpack melt, could lead to an increase in landslides on Mount Shasta (Rocha 2014; U.S. Geological Survey (USGS) 2020).
 |
| Figure 5. RCP 8.5 climate change scenario % change in total annual precipitation for the 2090s in Northern California. Source. |
Douglas Firs will likely be the most affected by climate change, due to the associated increase in frequency and severity of wildfires. Douglas Firs take roughly 40 years or more to develop thick, low to medium fire intensity resistant bark, making them less resistant to wildfire than other native trees (Steinberg 2002). The seeds of Douglas Firs are also destroyed by high severity crown fires, meaning an increase in fire frequency and intensity could greatly reduce the bounce-back of Douglas Fir populations following a fire (Anderson 2008; Steinberg 2002).
Conservation Plan
Vulnerability
The forest itself is the most vulnerable to ground-level ozone pollution. A large portion of the forest is dominated by Ponderosa Pine, which is sensitive to ground-level ozone and shows noticeable leaf damage when exposed to ozone (U.S. NPS 2019). Smog, which contains ground-level ozone, can get trapped at lower elevations by inversion from warm continental air or high pressure systems, making the lower elevation forest more vulnerable to ozone pollution (Huber 2004).
Of the three regions of the Shasta National Forest, Mount Shasta is the most vulnerable to climate change. Mount Shasta is expected to experience a ~10℉ MDAT increase to ~50℉ by the 2090s under the RCP 8.5 climate change scenario (U.S. Global Change Research Program 2021). This temperature increase will reduce winter snowpack, thus reducing the amount of spring snowmelt water and negatively impacting the systems and native species that rely on spring snowmelt (EPA 2020; NRCS 2021). Additionally, the increase in MDAT caused by climate change will cause upslope shifts in ecosystems and species found on Mount Shasta and could eventually lead to the extinction of high-elevation species (Freeman et al 2018).
Mount Shasta
Mount Shasta’s vulnerability is primarily from climate change, which is a global issue / phenomenon. A large part of the conservation effort should be towards encouraging the reduction of fossil fuel use, encouraging the use of renewable energy sources, and towards monitoring the yearly snowpack at higher elevations. Reducing fossil fuel use at the state level will be beneficial and achieved through maintaining California’s emission laws and the further implementation of renewable energy. Since climate change is a global issue, state-wide reduction in greenhouse gas emissions will not be enough to stop the progression of climate change. However, monitoring of winter snowpack and temperatures will at least tell managers how Mount Shasta is responding to climate change.
Shasta Forest
Vulnerability in the forest itself primarily comes from increased frequency and severity of wildfires caused by climate change and ground-level ozone pollution. As discussed above, climate change is a global issue that will take international cooperation to solve. Wildfire frequency and intensity can be managed in several ways. The likelihood of wildfires, especially accounting for how climate change is affecting fire seasons, can be published daily to alert the public to possible fire danger, and burn bans can be put in place during higher risk periods. Regular manual removal of potential fuel and carefully controlled low intensity controlled burns can reduce fuel loads in an effort to reduce the intensity of future wildfires.
Ground-level ozone can be mitigated by maintaining California’s stricter emission laws and implementing the use of more renewable energy sources. However, since a large portion of the ozone pollution affecting the Shasta National Forest is blown over the Pacific from China, state-wide reductions in fossil fuel use will only help to a certain extent (Lin et al 2014). As found by the Lin et al (2014) study, encouraging the purchase of locally made products as opposed to products produced overseas could help reduce the amount of pollutants produced by industry in China, and thus reduce the amount of pollutants that get blown over the Pacific ocean into California.
Lake Shasta
Lake Shasta’s vulnerability primarily comes from invasive species, as the lake is man-made and commonly used for sport fishing (Northern California Water Association (NCWA) 2021; U.S. Department of Agriculture & U.S. Forest Service 2015). Non-native aquatic species can invade in a number of ways, including by hitchhiking on or in watercraft, fishing gear, and ballast / bilge water or through the release of unwanted live bait (StopAquaticHitchhikers! 2017c). The Clean Drain Dry Procedure can be used by individuals to prevent the invasion of non-native aquatic species, and this procedure can be promoted, taught, and enforced to reduce the likelihood of an invasion (Figure 6, StopAquaticHitchhikers! 2017a).
Figure 6. Example of the Clean Drain Dry Procedure that is enforced by the state of Minnesota to prevent the spread of invasive aquatic species. Source.
Comments
Post a Comment