Ecological Role of Cattle at Point Reyes National Seashore: Effects of Grazing History on Coastal Plant Communities

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

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