Results of a Biological Survey of a Site for a Proposed Removal of Eucalyptus globulus at the Forest of Nisene Marks State Park, Santa Cruz County, California
Prepared for the California Department of Parks and Recreation
Prepared by Mary Friedman
November 19 2020
A biological (Threatened, Endangered, and Sensitive [TES] Species) survey at the Forest of Nisene Marks State Park was conducted. A list of the invasive exotics of priority concern within the park was useful in determining the survey’s focus. The survey’s species of focus, Eucalyptus globulus was chosen based upon its A-1 classification as a most invasive wild pest plant that disrupts natural habitat (Fig. 1). To abide with National Environmental Policy Act (NEPA) regulations, the proposed project uses “practicable means” in order to benefit the environment (Czarnezkit, 2003). Accordingly, the proposed project calls for only slightly modifying the site by removing a single type of invasive species rather than eliminating all the most invasive species at one time. The area surveyed was a section of the park containing Eucalyptus globulus to consider effects of removing the tree species.
Eucalyptus globulus is a subject of intense unease in California (Lopez 2015). Eucalyptus globulus grows best in the California coastal fog belt and is most invasive on coastal sites exposed to summer fog drip (Boyd, 2000; Skolmen & Ledig, 1990). Its aggressive growth, invasive quality, and association with fire make the ceasing of its spread important (Lopez 2015). The invasive species removal project proposal aligns with renowned conservationist Aldo Leopold’s “Land Ethic” and the values of the park’s founders. Leopold’s “Land Ethic” supports protecting the environment, and interfering with the degree to which non-native plant species are invasive to the ecological community is a way to practice stewardship (Leopold 2013). Further, Nisene Marks, a woman who instilled the sense of stewardship in her children, was the original owner of the confines before it was deeded to the State of California via The Nature Conservancy in 1963 (The Forest of Nisene Marks 2003). Therefore, insofar as the current stakeholders are aiming to fulfill the original owner’s vision for the space, it is logical to approve the project. A principle, embedded in the project, that Leopold would agree with is that humans have the ability to change their relationship with the land from one of exploitation to one of management and stewardship. Between 1883 and 1923, over 150,000,000 board feet of lumber flowed down the railroad line and out to markets all over the world (The Forest of Nisene Marks 2003). Afterwards, the loggers abandoned their buildings, pulled up the railroad rails, leaving behind a scarred and brutalized landscape (The Forest of Nisene Marks 2003). Scientists Holly Jones and Oswald Schmitz (2009) investigated the recoverability of ecosystems under the prediction that ecosystems will take centuries to recover from damages if they recover at all. However, their research across 240 independent studies showed most ecosystems can recover from major human impacts on timescales of decades to half-centuries insofar as proceeding actions bring the ecosystem back to conditions that empower its health (Jones and Schmitz 2009). That said, the proposed project brings potential to contribute to a positive ending of the brutal story. The evaluation was executed to determine how the proposed action would impact the Forest of Nisene Marks State Park’s threatened and endangered species protected by the Endangered Species Act or California State regulations shown in Appendix B (Forest of Nisene Marks State Park 2003). First, it is important to understand the consequence of inaction. Davies and Sheley (2007) estimated invasive species contributed to 35-46% of the plants and animals placed on the United States Federal Endangered Species List. Particularly, Eucalyptus globulus spreads and disturbs vegetation communities if enough moisture is available for propagation, state resource manager David Boyd conveyed in a report for the California Invasive Plant Council (Gross 2013). After becoming settled, the trees change sun exposure, nitrogen mineralization rates, soil moisture, soil chemistry, and fire patterns (Gross 2013). Further, the trees presence leads to a large amount of fuel resting on the ground floor as they shed peeling components (Fig. 2). Additionally, in fires, volatile compounds in foliage lead to massive burning (Gross 2013). That said, the proposed project would crucially mitigate damage the Forest of Nisene Marks State Park may experience from future wildfires. Local residents who aim to protect their shelters and visitors who regularly use the park would strongly support the proposed action. Research shows the public is more concerned with managing invasive species for intrinsic environmental worth than economic benefit and that preventing further environmental degradation is more motivating than promoting additional environmental gains (DeGolia et al. 2019). Therefore, the costs of the project need to be considered with public preference in mind.
To be responsive to NEPA, this report suggest multiple ways to fulfill the project’s purpose to a range of degrees (National Park Service U.S. Department of the Interior 2006). Eucalyptus globulus management takes many forms as it can entail simply removing lower limbs, thinning trees, or removing entire stands (National Park Service U.S. Department of the Interior 2006). While the preference is for the entirety of all trees to be removed for the purpose of preserving biodiversity in the surrounding area, simply removing lower branches would increase fire safety (National Park Service U.S. Department of the Interior 2006). In order for the technique to be effective in terms of increasing fire safety, branches up to a minimum of 10 feet off the ground must be removed (National Park Service U.S. Department of the Interior 2006). Although the least extensive version of the project would yield minimal benefits, it would not require the highly technical skills and equipment needed to completely remove large trees. For example, harnesses may be needed to lower the largest trees in sections (National Park Service U.S. Department of the Interior 2006). Additionally, left untreated, stumps will re-sprout, and will need to be cut again (National Park Service U.S. Department of the Interior 2006). Stumps can be treated with Glyphosate herbicide around the circumference where the actively growing cambium layer is (National Park Service U.S. Department of the Interior 2006). Grinding to destroy the stump is also done, but is labor intensive and is sometimes not feasible (National Park Service U.S. Department of the Interior 2006). Tarping with heavy plastic prevents re-sprouting with light deprivation and a physical barrier (National Park Service U.S. Department of the Interior 2006). Further, once eucalyptus is cut, an area is vulnerable to invasions by other non-native plants (National Park Service U.S. Department of the Interior 2006). Complete site restoration involves collecting local seed, growing native plants in a nursery, transplanting seedlings, and monitoring them until they get established (National Park Service U.S. Department of the Interior 2006). While the site is being restored with replacement vegetation, vigilant weed removal must also be in progress to sustain the health of the newly planted native species. These projects provide many opportunities for public involvement (National Park Service U.S. Department of the Interior 2006). The removal of Eucalyptus globulus would enable a planted native species aligned with the conditions of the area to grow in place of it. Eventually, the vegetation would be tolerant of the conditions it imposed upon itself. Moreover, the terminal community would be at equilibrium between gross primary production and respiration.
The proposed project site was surveyed on days ranging from October 1 to October 23 2020, by University of Denver student, Mary Friedman. She gathered data on October 1, October 5, October 8, October 12 and October 19 from 9-10am. She gathered data on October 3, October 7, October 10, October 14, October 17 and October 21 from 3-4pm. Her activity consisted of a pedestrian survey and field survey at the park. The pedestrian survey entailed observing the people who walked by and their respective changes to the space, and inquiring about their knowledge of the species surrounding the Eucalyptus globulus. The practice aligned with Leopold as he views humans as a useful subset of the animal population rather than being only a source of disturbance to the space (Leopold 2013). The field survey entailed taking note of the large-scale area surrounding the Eucalyptus globulus. The survey consisted of an examination of Bridge Creek Trail extending off of the Loma Prieta Grade (Fig. 3). Specifically, the survey spanned from the Porter House Site to the Bridge Creek Historic site (Fig. 3). It involved walking throughout the site and seated observation close to the Eucalyptus globulus. Particularly, the field survey focused on identification of species surrounding the Eucalyptus globulus. By visiting the site on various days at various times, Ms. Friedman was able to gather a range of preliminary observations. Vegetation was portrayed and classified according to a physiognomic class system designed by Dick-Peddie (1993) and physical disturbance levels, as suggested by the U.S. Fish & Wildlife Service (1980) and additional resource management agencies (Frye, 1995).
That said, Ms. Friedman conducted observations of Eucalyptus globulus, and the surrounding, listed state and federal threatened or endangered sensitive species and their habitat characteristics. These habitat qualities were considered with habitat available at the survey’s area. Further, the threatened and endangered species still need to be able to have their dietary needs satisfied and reproduce. If possible habitat for any listed species occurred near the Eucalyptus globulus, additional assessment of the possible effects of the proposed project on the species was carried out. Major waterways were also evaluated as part of the habitat assessment and the threatened and endangered species review. Additionally, Ms. Friedman used systematic grid sampling as part of her survey method. She positioned quadrats along a set of line transects. Specifically, she placed a quadrat every two meters along the transect starting from the non-native plant. She did it this way because it can be difficult to count individual plants considering they merge into one. A grid quadrat makes it easier to notice the percentage of the square covered (Biology Practicals and Revision Biology Tutor). This method worked well for this project because the transect needed to be placed based upon the presence of the non-native plant and therefore could not be completely random as the survey focused on understanding the non-native species and their effect on native plant species. The specificity involved in the systematic grid sampling methodology provides precise, useful information to the California Exotic Pest Plant Council as it verified where the contamination is present in the park and provided information on spatial and temporal patterns. The data thoroughly communicates the need for invasive species management to the Department of Parks and Recreation with a high level of confidence needed to acquire funds necessary for managing the invasive species. There are a variety of issues to consider with respect to how the removal of Eucalyptus globulus would impact the ecological character of the area. Specifically, measuring landscape connectivity, the extent to which a landscape facilitates the movements of organisms and their composition, revealed whether the proposed removal would bring significant changes to the area (Rudnick 2012). The assessment was useful in determining the degree in which the space is sensitive to the proposed changes (Nichol and Chadès 2017). For optimal protection of the area it is essential to account for the variables underlying the major ecosystem services the area delivers, and the threats upon them (Hummel et al. 2017). Results and Recommendations Vegetation & Habitats The large amount of moisture and sun exposure in the riparian and stream areas found frequently along Bridge Creek (Fig. 3) support a variety of vegetation and animals compared to the redwood forest itself. The section of the park south of the Porter Picnic Area (Fig. 3) has trails within or close to creek drainage revealing some erosion. Consequentially, there are issues with sedimentation mostly existing in sections areas of bare soils. Trails on the flat section above the creek have very little ground vegetation, which creates bare ground vulnerable to erosion. Slightly north of Love Gulch there are six eucalyptus trees present on both sides of the Loma Prieta Grade Trail (Fig. 3). The forest border in the observed area is largely Douglas-fir tanoak chaparral and primarily redwood. Invading Eucalyptus globulus is particularly a threat to maritime chaparral, coastal scrub, and Coast Live Oak woodlands (Lopez 2015). In general, Eucalyptus globulus leads to nearby crop suppression and possible allelopathy suppressing ground vegetation which explains the soil erosion (Rejmánek and Richardson, 2011). Eucalyptus globulus, therefore, facilitates its own success at the expense of native plants and reduces desirable plant diversity (Bell et al., 2007).
Wildlife Observed wildlife include mammals such as mule deer (Odocoileus hemionus) and domestic dogs (Canis familiaris), and invertebrates such as the banana slug (Ariolimax columbianus). Relatively few domestic dogs enter the section where Eucalyptus globulus is present because it exists so far north in the park and there are many other areas that are more populated by humans. Further, domestic dogs are technically not allowed on the route where Ms. Friedman completed the survey. In general, Eucalyptus globulus has poor wildlife value (Rejmánek & Richardson, 2011). The wildlife are impacted by the Eucalyptus globulus because of animal dependency on relatively lower tiered members of the ecosystem’s trophic structure. That said, returning flora and fauna communities to their interdependence with other native plant and animal species crucially helps to maintain the park’s biodiversity (Leopold 2013). Leopold’s “January Thaw,” reveals the importance of biodiversity in maintaining trophic structure. The hibernating skunk’s decision to uncurl himself and venture out to explore the wet droplets from post-blizzard conditions manifested a series of predator-prey relationships. When the skunk created tracks near the meadow mouse’s underground haystacks, the meadow mouse went out into plain sight and was eaten by the hawk (Leopold 2013). Similarly, the rabbit fearlessly darted out of the winter depths only to be eaten by an owl (Leopold 2013). The owl and hawk superiorly adapted to be able to respectively feed on the rabbit and mouse. However, if the rabbit and mouse did not exist due to some source of biodiversity loss, neither would their owl and hawk predators. Without the implementation of the proposed project, Eucalyptus globulus would continue wiping out components of the forest that certain native predators are reliant upon. Without food sources available, the animal populations who feed on the wiped out plants would eventually cease to exist. As a result, high-level animal populations who feed on the herbivores would have no prey and also struggle to exist. Further, cascading trophic interactions are often defined as the indirect effects of a predator on primary producers through the effect of the predator on herbivores (Naddafi and Rudstam 2013). Predator biodiversity impacts producers just as much as producer biodiversity impacts predators. With the change in vegetation as a result of the continual spreading of Eucalyptus globulus, certain herbivores may adapt to a loss in their own prey by going after the prey of another animal species. Essentially, it would alter competition dynamics amongst animals. A species of plant experiencing abnormally high rates of predation would struggle to survive. However, insofar as there is diversity of life forms in all levels of the system, the less a given trophic structure relies on a certain species to maintain its structure. A study found interference among predators in multi-species treatments weakens the consumptive cascading effects of predation on lower trophic levels (Naddafi and Rudstam 2013). That said, the invasive quality of Eucalyptus globulus has a detrimental impact on the site’s biodiversity which would limit the trophic structure’s complexity and weaken the ecosystem’s health.
Threatened and Endangered Species The table in Appendix A lists endangered and threatened species (Forest of Nisene Marks State Park 2003). Observed TES bird species included the Cooper’s Hawk (Accipiter cooperii). Although the Cooper’s Hawk nests in Eucalyptus globulus, in the case of the proposed project’s removal of the invasive species, the bird would nest in other large mature trees it prefers such as Douglas-fir (Haiman 2006). Its breeding season is February to October. That said, it is recommended those who are conducting the project proceed with caution, especially if the project is conducted during the breeding season. However, considering the Cooper’s Hawk ability to nest in various tree types (Haiman 2006), its existence as a TES species should not keep the project from being approved. Many bird species that do nest in Eucalyptus globulus do so in lower densities than native habitat (Suddjian, 2004). The Point Reyes Bird Observatory found nesting birds have greater nest survivorship in native vegetation (National Park Service, 2006). Moreover, eucalyptus globulus gives nesting birds false security (Williams, 2002). Observed TES vegetation include the Santa Cruz manzanita (Arctostaphylos andersonii), Coyote ceanothus (Ceanothus ferrisae), and Santa Cruz clover (Trifolium buckwestiorum). Santa Cruz clover has been characterized as a species of concern (Forest of Nisene Marks State Park 2003).
Observed migratory birds include the Steller’s jay (Cyanocitta stelleri), the American dipper (Cinclus mexicanus) on streams, and the belted kingfisher (Ceryle alcyon) nested near water. Migratory bird species are protected by the Migratory Bird Treaty Act from harm or take during the nesting season (Kay 2002). Scheduling all removal of Eucalyptus globulus in the survey area outside the nesting season is the optimal way to avoid adverse impacts to individual nesting birds (Kay 2002). A separate nesting bird survey before removal or monitoring during construction is recommended to avoid violations of the Migratory Bird Treaty Act (Kay 2002).
Two main wetlands near the survey area are Aptos Creek and Bridge Creek. Both flow in a steep canyon surrounded by lush ferns and flourishing vegetation. Bridge Creek runs from north to south, while Aptos Creek flows from east to west and down south. Bridge Creek is contained within the park and empties into Aptos Creek. Eucalyptus globulus can spread from planted locations in areas with adequate moisture, so they should not be continuing to exist near wetlands (Boyd, 2000; Steinmaus, Rejmánek, Ritter, Jasieniuk, & Knight, n.d.; Rejmánek & Richardson, 2011) and the proposed project would prevent it from doing so. Further, it is problematic for eucalyptus leaves to fall into streams as it alters the trophic structure amongst the aquatic animals, likely because the chemical content of eucalyptus leaves contrasts the composition of native foliage (Gross 2013). It is crucial debris from cutting down the Eucalyptus globulus does not fall into the wetlands to abide with NEPA guidelines (National Environmental Policy Act 2020). Debris left over from vegetation management activities includes branches, leaf litter, and tree trunks. Larger materials may be hauled away to a composting site or a landfill, or cut into logs for firewood (National Park Service U.S. Department of the Interior 2006). Material up to 24” in diameter can be chipped and used as mulch or to generate electricity (National Park Service U.S. Department of the Interior 2006). Burning debris piles is another option and is often the most cost-effective approach (National Park Service U.S. Department of the Interior 2006). Regardless of the disposal method, it is crucial to the health of the park’s wetlands that scraps be collected everyday during the proposed project’s conduction before leaving the premises.
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