Ecological role of cattle at Point Reyes National Seashore: effects of grazing history on coastal plant communities
Martin Arceo1, Riley Content-Castro2, Jacques Jougla3, Laurel Teague4
1 University of California, Riverside; 2 University of California, Santa Barbara; 3 University of California, Berkeley; 4 University of California, Santa Cruz
ABSTRACT
There is ongoing debate over the effectiveness of cattle grazing as a prospect for plant community conservation. Since the National Park Service acquired the land at Point Reyes Seashore, controversies over whether ranching should continue in the protected area have defined part of the park’s public image. Resolving uncertainties over impacts of cattle on the Point Reyes landscape could inform these debates and lead to viable long-term management strategies. In this study, we examine grassland species richness and composition under four different grazing land-use histories throughout the park (active grazing and 17, 39, and 87 years-since-grazing). Results point toward positive effects of active grazing on native forb richness through suppression of the invasive grasses Holcus lanatus and Festuca perennis. We find steep declines in native plant richness and abundances in the early decades following cessation of grazing and subsequent partial recovery of native species over longer timescales. Our research suggests that cattle foraging impacts plants according to functional group more than provenance. Cattle grazing and associated disturbances may have promoted the initial introduction and establishment of exotic plants into the Point Reyes landscape, but with exotic plants now well established throughout California and most native grazers absent or severely declined, new research suggests that cattle fill an important ecological role in promoting coexistence by native species on exotic-dominated landscapes.
INTRODUCTION industries it places extreme demands on the ecosystems that support it. As the Agriculture is fundamental to the human population continues to grow, so United States economy and to the too do our demands on natural health and well-being of the American resources, our potential impacts on people, and as with many large
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 1/14
these resources, and our need to fully In California, agriculture is a major understand these impacts so we can part of the state’s history, economy, assure continued delivery of critical society, politics, and ecology. resources. California’s economy is the sixth largest in the world of which agriculture plays a Animal agriculture provides food and huge part (CA Department of Finance, consumer products, jobs, and a rich 2017). This stems from the unique and culture deeply rooted in American complex geology of the state, which society. Prairie and grassland creates a diverse range of terrain and productivity is especially critical to climates, creating the habitats which in humans, with grains constituting over turn support one of the most 50% of the calories we eat (Awika, agriculturally productive regions in the 2011). But our use of these ecosystems world. In particular, California coastal comes at a huge ecological cost as grasslands as well as the Central Valley animal agriculture—and in particular grasslands host a tremendous amount large ungulate species—can impact far of fertile agriculture. However, these more than just the grassland grasslands are under threat both from communities on which they feed. increasingly restrictive droughts over Animal agriculture affects terrestrial, the past 30 years in addition to an riparian, and aquatic environments incredible amount of exotic invasion. through trampling, fine sediment Animal agriculture, in its dynamic deposition, manure dumping which can nature, both effects and is affected by cause eutrophication, and water both. The most water intensive crops in diversion (Belsky et al. 1999). On a the state are alfalfa and other cattle global scale animal agriculture forage, with meat and milk products generates large quantities of themselves consuming 22 and 7 percent greenhouse gasses, concentrates huge of a US consumer’s daily water amounts of toxic waste into waterways, footprint, respectively (Hoekstra & which results in oceanic dead zones, and Mekonnen, 2013). Interestingly, the is the leading cause of deforestation drought and increasing water use from around the world (Koneswaran & these crops may actually be Nierenberg, 2008, Diaz & Rutger, 2008). exacerbating the invasion of exotic Within the United States, animal species (Harrison et al. 2015). Invasive agriculture requires more freshwater European grasses have become the than any other agricultural product in dominant biomass across California’s the United States (Hoekstra & grasslands, and native biodiversity has Mekonnen 2012). As such, agricultural suffered a huge decline because of their practices must balance production and invasion. But just as they may be efficiency with its environmental, social, exacerbating the problem, cattle and and political impacts. grazing are increasingly relevant as a conservation effort (Pasarai et al. 2014). Cows have co-evolved alongside the
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 2/14
quick-growing European annuals and and ecotourism for the elk as well as the may therefore decrease their spread interests of the ranches that operate through selective grazing. Clear within the Park. Today, the ranches are understanding and full accounting of operating under five-year contracts with these concerns can only help as we seek the National Park Service. Since these to manage our natural resources to the contracts and the continuation of best of our ability. California sets the ranching itself are currently in debate in perfect stage for this debate, as Point Reyes National Seashore, it is nowhere else in the country do debates critical to understand the impact cattle over agriculture rage more than in this grazing places on grassland plant state—the most agriculturally abundant communities in time to make the best and one of the most environmentally decisions for all stakeholders. progressive. In this study, we examine the effects Perhaps the epicenter of the debate of cattle grazing and time since over conservation and ranching is found cessation of cattle grazing on coastal at Point Reyes National Seashore. Point grassland plant communities in Point Reyes has historically cattle grazed land Reyes. We test for differences in plant that has been slowly phased out of species richness and plant species ranching and replaced by Tule Elk composition between habitats with (Cervus canadensis nannodes) habitat. active current cattle grazing and those Point Reyes as a National Park presents from which cattle have been removed as an ideal location for studying across a chrono-sequence of removal. grassland ecology because the grazing Native plant diversity is an important histories of the parcels of land are all measure of overall biodiversity and publicly available, and as the National ecosystem health. This research will Park Service shut down ranching help us to understand how cattle affect operations across decades, it acts to the ecosystems they graze in, at a time conserve the land across a timeline. when this very issue is being debated Over the previous decades, the elk built over within this national land. up their populations, resulting in the still active ranching operations feeling METHODS increasingly at odds with the elk Natural History of the Study System populations, due to competition over forage and water as well as the Point Reyes National Seashore destruction of fencing (Elk Fences Now, (38.0723° N, 122.8817° W), 2014). Additionally, paratuberculosis, a encompasses over 280 square disease passed from cattle to the elk kilometers along the Northern California herds, is blamed for a more recent coast. The Mediterranean climate of population decline of the elk. The Point Reyes is characteristic of the National Park Service now must balance California coast, with mild, wet winters the interests of conservation, welfare, and cool summers. The average January
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 3/14
temperatures range from 7.3° C to 12.3° level analysis on Velvet Grass, Italian C, while the average September Wild Rye, and Wild Radish as they are temperatures range from 10.9° C to considered highly invasive within the 16.1° C. Annual precipitation levels Point Reyes peninsula and previous average 433 mm, with heavy fogs studies have established these species providing considerable moisture in the as potentially sensitive to grazing summers. Geologically, Point Reyes regimes (U.S. National Park Service; National Seashore is separated from Johnson & Cushman, 2006). Additionally most of the continental United States by we focused on the native species the San Andreas Fault, which creates a Coyote Brush (Baccharis pilularis) as an geologically complex area resulting in a individual species as it is a successional variety of soil types and vegetation species and may be used as an indicator assemblages. The Seashore has a for successional stage post-grazing plethora of ecosystems, comprising of (Elliott & Wehausen, 1974). dunes, beaches, coastal grasslands, wetlands, chaparral, wilderness lakes, Land Use History and Douglas Fir (Pseudotsuga menziesii) Point Reyes National Seashore has an and Bishop Pine Forests (Pinus extensive history of land use muricata) (U.S. National Parks Service development. Predating written history 2017). by 5000 years, the Miwok Native Point Reyes hosts high biological Americans were the first inhabitants of diversity and represents 15 percent of the land until the Spaniards seized the California's flora. It is home to 900+ region in the early 1800s. This was vascular plants, of which 61 are followed by the establishment of cattle endemic to the region, and over 50 are ranches and agricultural operations listed as rare, threatened or throughout the region, soon followed by endangered. However, 292 species in the introduction of invasive European Point Reyes are non-native, and often grasses. During the California Gold Rush, these exotic species are highly invasive Tule Elk, an abundant grazer in the (U.S. National Park Service 2017). region, saw a dramatic decline in Invasive species are the second highest population due to widespread hunting threat to biodiversity, threatening 49 as well as displacement from cattle. Tule percent of endangered or threatened Elk were thought to be extinct until species (HilleRisLambers 2010; Wilcove Henry Miller, a ranch owner, discovered et al. 1998). Exotic annual grasses such the last remaining herd of Tule Elk in his as Italian Wild Rye (Festuca perennis), property in 1874. Point Reyes National and Slender and Wild Oats (Avena Seashore was established in 1962, and barbata, Avena fatua), and perennials Tule Elk were reintroduced to Point such as Velvet Grass (Holcus lanatus) Reyes in the early 1970s. In 1978 the have invaded the coastal grassland of 10.5 square kilometer Tule Elk reserve Point Reyes. We focused our species- was created and fenced off from the
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 4/14
cattle, and since then Tule Elk one of the first dairies at Point Reyes, populations have increased to an and operated from 1859 to 1930 estimated 3900 individuals and 22 herds (Livingston, 1993). Cattle were excluded throughout the Point Reyes Peninsula. from Pierce Point Ranch in 1978 to While Point Reyes National Seashore is create the Tule Elk Reserve, which we public land, the National Park Service used as the 39-years post-grazing site has made a commitment to preserving (U.S. National Park Service 2017). The the long-run agricultural and cattle Historic D Ranch, our 17-year site, ranch industry in addition to supporting operated until 2000, when it was closed the Tule Elk population. Today, Point down to restore both the historic Reyes National Seashore is a structures and the native vegetation conservation enterprise visited by (Dave Press, Personal Communication, thousands of researchers, students, and August 2017). There are approximately to tourists looking to explore the unique 28,000 acres of active cattle and dairy landscape, flora, and fauna (U.S. operations within the park, and as such National Park Service 2017). we chose our active grazing areas primarily on accessibility (U.S. National Research Design Park Service 2017). Additionally we We selected sites with different attempted to sample a balance of both grazing histories, which we defined as cattle and dairy fields to account for years since active grazing. In total we potential variation in management had four distinct grazing treatments- practices between ranches. sites, which were currently grazed, and Tule Elk, Point Reyes’ native large sites, which had not been grazed for 17 ungulate grazer, now occupy all of the years, 39 years, and 87 years. (Figure 1). inactive graze sites we sampled. Both the 17-year D ranch site and the 87-year Muddy Hollow site are occupied by free- range elk herds, while the 39-year Tule Elk Reserve herd is isolated from active graze sites by an elk fence. As such our former grazing sites provide a glimpse into what the park may look like should cattle ranching be removed and the peninsula returned to the elk. Figure 1. Point Reyes Site Location Map by Grazing Regime. 33 total microsites were sampled over the Point Reyes peninsula, ranging from currently grazed to 87 years-since-grazing.
The 87-year site was the former Muddy Hollow Ranch, now the location of Muddy Hollow trailhead. The ranch was
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 5/14
33) (Figure 2). Along the 25m transects we placed quadrats at 5m intervals with alternating positions to the left or right of the transect tape, which was determined haphazardly (N = 330). The quadrat area was 2500 cm2, which was divided into 25 smaller squares of 100cm2.
We measured plant abundance and richness within each meter square quadrat. To measure species richness we identified all of the species which were present within our quadrat and marked them as present, then later Figure 2. Research Schematic. Within each compiled a list of all species seen at all grazing regime (black rectangle), we generated the sites and determined which species three sites (blue circle). At each site, we were absent. We used point intercepts generated another three GPS points within a 150-meter radius of the original site as our to measure relative abundance, and microsites (red “L”). Each microsite consisted of counted each time a species crossed two 25 meter transect lines going west and one of the 16 intercepts as one hit. north. Along the two transect lines, we used a point-intercept technique to sample from Statistical Analysis 2500m2 quadrats (red square) spread out every 5 meters along the transect lines. Prior to comparisons, we ran tests of unequal variance in order to determine We conducted field sampling of the appropriate method of analysis for grassland communities for plant species each variable. We ran Kruskal-Wallis richness and relative abundance across Tests for richness, Velvet Grass (Holcus multiple grassland sites on the Point lanatus), Italian Wild Rye (Festuca Reyes landscape. Sampling was perennis), and Coyote Brush (Baccharis conducted August 3rd through 6th, pilularis) abundance all by years-since- 2017. We selected three GPS points grazing. We also ran a regression on within each grazing regime to use as a species richness by Italian Wild Rye midpoint (N = 11; one site was excluded abundance. We considered these due to overwhelming poison oak). species to be important or characteristic Within a 150-meter radius from the GPS species of these ecosystems and worthy midpoint point we generated three of individual relative abundance additional GPS points via a random analysis. point generator, hereafter referred to as microsites (geomidpoint.com). At each Plants were classified as exotic or microsite we measured two 25 meter native and either grasses or forbs transects to the North and West (N = creating four categories along with a
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 6/14
fifth category for shrubs. For the rest of The highest richness occurred at these comparisons we summed our currently grazed sites and lowest quadrat data in their microsite, reducing richness occurred at 17 years post number of replicates but allowing us to grazing sites (Figure 3). Kruskal-Wallis look at larger scale trends. We determined there to be significant performed an ANOVA on abundance in variation in Velvet Grass correlated to each of these categories against years- years-since-grazing (�2 = 48.04, P < since-grazing. We also performed ANOVAs 0.0001). Velvet grass had its highest on native and exotic species richness as abundance at 39 years-since-grazing well as proportion of native species by sites, and its lowest abundance at years-since-grazing. The actual native currently grazed sites (Figure 4). proportion for each grazing regime was calculated from total native and overall richness values for each site. We also analyzed species composition of transect level relative abundance data using nonmetric multidimensional scaling.
RESULTS
We found a total of 63 species over 330 quadrats in 4 different regions of varying cattle grazing history. A Kruskal- Wallis test showed significant difference Figure 4. Velvet Grass Abundance by Grazing in plant richness explained by years- Regime. Mean quadrat-level Velvet Grass 2 abundance is plotted by time since grazing. since-grazing (� = 98.15, P < 0.0001). Velvet grass abundance increases after removal of grazing until reaching a maximum at 39 years post grazing at which point it decreases. (�2 = 48.04, P < 0.0001)
Kruskal-Wallis also found Italian Wild Rye abundance to vary significantly with changes in years-since-grazing (�2 = 76.42, P < 0.0001). Italian Wild Rye had its highest abundance at 17 years post grazing sites and lowest abundance at Figure 3. Plant Species Richness by Grazing 39 years post grazing sites (Figure 5). Regime. Mean quadrat-level species richness for all grasses, forbs, and shrubs are plotted by time We found a significant negative since grazing. Sites where active cattle grazing association between species richness was observed showed the most species richness and Italian Wild Rye abundance (R2 = when compared to sites without cattle grazing. 0.268, P < 0.0001; Figure 6). (�2 = 98.15, P < 0.0001)
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 7/14
Figure 7. Coyote Brush Abundance by Grazing Regime. Mean quadrat-level Coyote Brush Figure 5. Italian Wild Rye Abundance by abundance is plotted by time since grazing. The Grazing Regime. Mean quadrat-level Italian lowest abundance was found at 17 years post Wild Rye abundance is plotted by time since grazing sites while the highest abundance was grazing. Abundance increases initially after found at 87 years post-grazing sites. removal of cattle until after 39 years it decreases to near 0. (�2 = 76.42, P < 0.0001) We found significant differences in abundance of exotic forbs by years- since-grazing (F = 3.404, P < 0.05; Figure 7). Exotic forb abundance was significantly higher in 17 years-since- grazing sites than 87 years-since-grazing sites (Tukey < 0.05). We found significant differences in abundance of native forbs by years-since-grazing as well (F = 6.034, P < 0.005; Figure 8).
Figure 6. Species Richness by Italian Wild Rye Abundance. Mean quadrat-level species Native forb abundance was richness is plotted on the y-axis as explained by significantly higher in currently grazed Italian Wild Rye Abundance. A Regression was sites than both 17 and 39 years-since- run and found a negative correlation between the two. (R2 = 0.268, P < 0.0001) grazing sites (Tukey < 0.05). For exotic and native grasses as well as shrub Relative abundance of Coyote Brush abundance, we found no significant was also found to be significantly different with time since grazing using difference associated with variation in 2 years-since-grazing (P > 0.05; Figure 9). Kruskal-Wallis (� = 43.56, P < 0.0001; Figure 7). Coyote Brush had its highest abundance at 87 years-since-grazing sites and lowest at currently grazed sites.
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 8/14
We found the highest total richness, 39 species, as well as highest proportion of native species, 53.85 percent, in the currently grazed sites. We found the lowest richness, 21 species, in the 87 years-since-grazing sites but the lowest proportion native, 33.33 percent, in the 17 years-since-grazing sites (Figure 10). Figure 8. Native and Exotic Forb Abundance by Grazing Regime. Mean Microsite-level abundance of Native and Exotic Forbs plotted on the x-axis as explained by years-since- grazing. Native Forb abundance is shown in blue while exotic abundance is in orange. Significant difference was found between exotic forb abundance between grazing regimes (F = 3.404, P < 0.05). Significant difference was found between native forb abundance between grazing regimes. (F = 6.034, P < 0.005) Figure 10. Proportion of Native Flora by Time Since Grazing. The richness of native plants as a ratio of the total plant richness for each grazing regime. The highest was 0.538 at currently grazed sites and the lowest was 0.333 at 17 years post grazing sites.
ANOVA determined there to be significant difference in exotic species richness explained by years-since- grazing (F = 3.342, P < 0.05). ANOVA found significant difference in native plant richness explained by years-since- Figure 9. Native and Exotic Grass Abundance by grazing (F = 7.847, P < 0.001). Precisely, Grazing Regime. Mean microsite-level we found that the 17 years-since- abundance of Native and Exotic Grasses plotted grazing sites had significantly lower on the y-axis as explained by years-since- native species richness than currently grazing. Native Grass abundances are shown in grazed, 39, and 87 years-since-grazing blue while exotic abundance is in orange. Exotic (Tukey < 0.05). The average proportion grasses exist in far higher abundance across all of native plants was shown to vary grazing regimes. No significant difference was significantly with changes in years-since- found between grazing regimes. (P > 0.05) grazing (F = 17.937, P < 0.0001). Specifically samples at sites 17 years
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 9/14
post cattle grazing had a far lower mean DISCUSSION proportion of plants that were native than all other sites (Tukey < 0.05). We found plant species richness varied significantly with grazing history on the Point Reyes National Seashore, but not in a linear or straightforward way. Quadrat-scale plant species richness was highest under current active grazing (mean = 6.011; Figure 3) While quadrat-scale plant species richness was found to be lowest in plots where grazing had been most recently removed (mean = 2.844; Figure 3). Plant species richness in grasslands where cattle were removed 39 and 87 years ago was intermediate between current Figure 11. Plant Composition by Cattle Grazing grazing and 17 years-since-grazing Regime Ordination. This plot accounts for 66.6 percent of variation within plant communities regimes. Among grazing treatments, organized by years since cattle grazing. Axis 1 currently grazed sites had the highest accounts for 36.6 percent of variation while axis variation in richness, which may be 2 accounts for 30 percent. Each colored box associated with differences in location represents the potential range of community permitting increased community composition according to our data, with overlapping regions sharing similar relative differentiation. However the high species abundances. average richness at currently cattle grazed sites may also be attributed to Nonmetric multidimensional scaling disturbance facilitated coexistence. returned ordination results for plant Cattle grazing at intermediate levels, composition by cattle grazing regime considered as an anthropogenic (Stress for 3d solution = 11.2289, disturbance have been found to lead to instability = 0.0000, Figure 11). Though a increased levels of vascular-plant 3-dimensional solution is recommended, species richness (Yuan et al. 2016). We our chosen axes represent the majority of found the invasive European grasses, the variation in species composition and Italian Wild Rye and Velvet grass, to therefore a 2-dimensional model is have significantly lower abundance satisfactory to represent the ordination. counts in currently grazed sites Axis 1 represents 36.6 percent while compared to the 17 years post grazing axis 2 represents 30.0 percent of plant sites, which suggests a feeding community variation. Variation in Wild preference in the cattle (Figure 4 & 5). Radish presence accounts for 42.6 This follows our hypothesis of selective percent of differences within Axis 1 grazing due to coevolution between the while variation in Velvet Grass abundance cattle and these invasive grasses. At explains 73.8 percent of Axis 2. moderate density, selectively grazing
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 10/14
free-range cattle may prevent these This is supported by our data as Coyote large seed load invasive grasses from Brush, a native shrub, had significantly dominating the ecosystem. Lower higher abundance at 39 and 87 years- density of these grasses may give slower since-grazing sites (Figure 7). This is reproducing native species a better assuming that the 87-year site had a chance of survival and propagation due similar composition to currently grazed to reduced competitive pressure. sites when it was an active ranch.
In the 17-year site, both Italian Wild Recent studies have found that plant Rye and Velvet Grass have far higher communities grazed by cattle abundance levels than in currently experienced greater native species grazed sites, which implies they are able richness and greater native forb cover to propagate at high success rates post when compared to ungrazed disturbance (Figure 4 & Figure 5). We communities (Beck et al. 2005). Our found a negative association between study confirms this precedent. We Italian Wild Rye abundance and plant found significantly higher native forb species richness, which suggests abundance in cattle grazed sites competitive exclusion, occurs as this compared to sites 17 and 39 years post species increases in abundance (Figure grazing (Figure 8). Native proportion of 6). This aligns with our finding of the plants is highest at currently grazed sites lowest richness at 17 years-since- as well (Figure 10) However, there is a grazing sites along with highest Italian trend for both native forb abundance Wild Rye abundance. Velvet grass has its and proportion native to increase from highest abundance at 39 years post the 17 years post grazing sites to the 87 grazing while Italian Wild Rye actually years post grazing sites suggesting that has its lowest abundance at this point. native plant species may take back Succession of dominant species is control of the ecosystem to some extent illustrated in our data by this change in after their initial fall after removal of Velvet Grass and Italian Wild Rye disturbance. abundance from currently grazed to 39 years-since-grazing (Figure 4 & Figure The nonmetric multidimensional 5). Velvet is lower in abundance that scaling analysis revealed over time plant Italian Wild Rye but both increase until composition becomes more varied, at the 39-year sites, Velvet Grass has even though richness did not increase become the most abundant and Italian accordingly. The presently grazed site Wild Rye has fallen to near 0 and the most recent 17-year site both appearances. Velvet Grass decreases in had the most constrained plant abundance at 87 years post grazing sites compositions along a singular axis, while which may be due to undisturbed, the 87-year site spanned almost the competitively superior species reaching entire range (Figure 11). The large a life stage in which they can better change in plant community composition utilize resources and exclude grasses. that occurs soon after removing
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 11/14
disturbance that we discussed variability seen amongst the current previously can be seen in the large shift grazing sites. in axes range from the currently grazed to 17 years post grazing sites. Some of While sampling the sites in the region the species, which were the primary that had been excluded from grazing for drivers of variation, were Asteraceae, 87 years, it became apparent that the Italian Wild Rye, Rattlesnake Grass, last three random GPS points that were Velvet Grass, Coyote Brush, and generated happened to land on terrain California Blackberry. Generally, exotics that sloped upward through thick explained the most variation along the overgrown scrubland dotted with axes, which may be due to their poison oak. This was our last day to disproportionate abundance relative to collect data preventing us from their proportion of the total richness. generating new points and sampling the Interestingly, even though the presently same number of quadrats for each grazed sites were most geographically region of grazing. This creates a separated, they were still constrained discrepancy in the precision to which we fairly well by microsite. measured the diversity of grassland plants between the region that has gone Experimental Concerns 87 years without cattle and the rest of the regions. When selecting the sites under current grazing, we chose the three Fog abundance varied across sites that areas to sample spread over the were more or less inland, potentially peninsula (Figure 1). Our other sites affecting the plant communities across within a particular grazing regime were our sites. This becomes especially geographically clustered much closer relevant considering that the tip of together. This distance between sites Point Reyes is the windiest and second could be responsible additional foggiest point on the North American variance. Additionally, Point Reyes continent (U.S. National Park Service National Seashore wildlife ecologist, 2017). Dave Press, explained to us that cattle and dairy operations use the land a bit Finally, of all the taxonomic families of differently as dairy cows must stay close plants, grasses are subjectively the most to the barn where they are milked and difficult to identify. When classifying the cattle intended for beef can roam the morpho-species we encountered in the full stretches of land available to them. field, each plant’s life history attributes The microsites we sampled under and distinction as native or exotic to current grazing had one site under beef California could have been misidentified cattle grazing and the other two under despite our best efforts to identify every dairy grazing. This creates two variables plant to the species level. that could explain the additional
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 12/14
Further Research Fences Now 2014). The ranching fees these organic ranches pay cost them To get a clearer understanding of the one tenth of the cost for an average effects of grazing on plant community organic ranch to operate on private land composition, more variables need to be (Center for Biological Diversity 2015). In accounted for. For example, it would be the 1960s, he Federal government beneficial to measure the average brought out these ranches for hefty height of the plants in each quadrat in sums of money, over $160 million order to understand how primary dollars in today’s money (Bancroft productivity differs from site to site. We Library, R.O.H.O. 1993). Many of them ultimately decided that it would be struggle even with the government difficult to compare these values effectively subsidizing their ranches (Elk because cow and elk herbivory removes Fences Now 2014). The extreme plant matter at different rates that we pressure of demand and competition cannot currently measure. Ungulate placed on commercial dairies and cattle density on the landscape also varied ranches operating on private land has between sites. At some sites there were driven the cost of their product down to elk herds calling out from the hills a point where sustainable practices can surrounding us, at other sites only dry barely survive, even with this support elk scat was observable. Attaining a from the government (Elk Fences Now measure of ungulate abundance per 2014). This results in a pseudo- area would allow us to control for this sustainable agricultural model that variability. becomes unfeasible for existing Economic Considerations ranching across the country due to the financial and land use constraints that Our findings indicate that some are levied against each organic cow. invasive plants, in particularly Velvet While this might be a historic and Grass, are less abundant in areas under valuable model for Point Reyes and the current grazing. We also found that National Park Service’s invasive plant native plant richness was greater in control efforts, this system is not areas of current grazing. These results economically feasible without the indicate that European cattle are support of the government. effective at controlling the invasion of exotic plants. This makes it appears as REFERENCES though the ranching management Awika, J. M. 2011. Major Cereal Grains approaches taken by the National Park Production and Use around the World. Service and the historic ranching Advances in Cereal Science: Implications to operations at Point Reyes create a Food Processing and Health Promotion:1– 13. sustainable model for cattle grazing. A significant issue with how these farms Belsky, A. J., A. Matzke, & S. Uselman. 1999. operate is that they struggle to makes Survey Of Livestock Influences On Stream ends meet ranching organically (Elk
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 13/14
And Riparian Ecosystems In The Western the National Academy of Sciences, 109(9), United States. 54:419–431 3232–3237.
CA Department of Finance. 2017. Gross State Johnson, B. E., & Cushman, J. H. (2007). Influence Product. Retrieved August 10, 2017, from of a Large Herbivore Reintroduction on
Hayes, G. F., & Holl, K. D. (2003). Cattle Grazing U.S. National Park Service (Point Reyes National Impacts on Annual Forbs and Vegetation Seashore). (2017). Retrieved 10 August Composition of Mesic Grasslands in 2017, from California. Conservation Biology, 17(6), https://www.nps.gov/pore/index.htm 1694–1702. Wilcove, D. S., Rothstein, D., Dubow, J., Phillips, HilleRisLambers, J., Yelenik, S. G., Colman, B. P., & A., & Losos, E. (1998). Quantifying Threats Levine, J. M. (2010). California annual grass to Imperiled Species in the United States. invaders: the drivers or passengers of BioScience, 48(8), 607–615. change? The Journal of Ecology, 98(5), 1147–1156. Yuan, Z. Y., Jiao, F., Li, Y. H., & Kallenbach, R. L. (2016). Anthropogenic disturbances are key Hoekstra, A. Y., & Mekonnen, M. M. (2012). The to maintaining the biodiversity of water footprint of humanity. Proceedings of grasslands. Scientific Reports, 6, 22132.
CEC Research | https://doi.org/10.21973/N3WW8C Summer 2017 14/14