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Research about Channel Islands National Park

Source-linked reports with geographic coverage including Channel Islands National Park.

10 recordsLinked to original sources
USGS2025

Analysis of trends in terrestrial vegetation at Mediterranean Coast Network Parks: Channel Islands National Park

The five islands comprising Channel Islands National Park (CHIS) experience natural gradients in temperature and moisture driven by ocean currents. Additionally, the islands were used as ranchlands and military land before becoming a national park, resulting in widespread erosion and vegetation change. As a result, CHIS spans gradients in climate as well as ranching duration and time since animal removal. Vegetation monitoring was initiated in 1984 on three islands (Anacapa, Santa Barbara, San Miguel), in 1990 on Santa Rosa Island, and in 1998 on Santa Cruz Island, with the goal of documenting the long-term response of island vegetation to ranch animal removal and climate fluctuations. Since that time, monitoring has documented the range of natural fluctuation in island environments over decades and provided insights into vegetation change in ecosystems unencumbered by ongoing development. Long-term vegetation monitoring at CHIS is therefore a rare example of an ecosystem experiment that demonstrates the results of management actions and serves as a baseline for land managers and scientists worldwide. Terrestrial vegetation data collected between 1984 and 2018 were modeled to estimate trends over time and to characterize relationships with covariates related to site characteristics, nonnative mammal removal programs, and water balance metrics. Data were analyzed for trends in vegetation cover, woody plant density, and plant community diversity grouped by life form and nativity across all islands and within individual islands, as well as for several individual species that dominate plant communities or present challenges to native plant recovery. In all, a total of 162 trend and covariate models were tested in this study, the details of which are provided in this report. Briefly, results reflect a decline in nonnative annual disturbance-thriving species with the reduction in animal grazing and trampling. Increasing trends were observed in native shrub density and native shrub recruitment density, as well as native shrub cover across all islands averaged together and on Santa Cruz Island. However, opposite trends were seen on the smaller islands of Santa Barbara and Anacapa, where increasing seabird activity may be damaging vegetation. Further results indicate the importance of soil moisture, relative humidity, fog, precipitation, site exposure, and solar radiation for vegetation patterns and trends. In many instances, there are apparent interacting effects of environmental variables with trends related to nonnative mammal removal and site location. Vegetation patterns in space and time emerge in the dataset as nuanced responses to interacting drivers.

Calfornia↗
USGS2024

Using surficial geologic maps, vegetation, and monitoring to address erosion impacts from grazing in Channel Islands National Park, California

Employing a map-unit classification scheme based on geomorphic process and age, the U.S. Geological Survey (USGS) mapped Quaternary surficial deposits of the five islands comprising Channel Islands National Park (CHIS), California, as no such maps previously existed. Mapping was motivated through an agreement with the National Park Service (NPS) to aid natural resource assessments, including post-grazing disturbance recovery and identification of mass wasting and tectonic hazards. The resulting detailed (1:12,000 scale) maps portray areas of upland erosional transport processes and alluvial, fluvial, eolian, beach, marine terrace, mass wasting, and mixed depositional processes at a scale commensurate with the process signal on the landscape. Detailed, GPS-located observations of sedimentology, pedogenic development, landscape position, and geomorphology constrain map unit identification. In addition, map-unit boundary delineation was determined in a GIS using a variety of high-resolution (sub-meter) aerial imagery and lidar-based DEMs complemented by derivative raster products. The GIS geodatabase schema used is GeMS compliant. Resolvable map-unit widths are as small as 10-15 meter. Locational accuracy of unit boundaries is estimated to be as low as 10 m or better. Detailed mapping is at a scale allowing determination of geomorphic transport processes operating on the landscape and conveys geologic information to land managers at a resolution commensurate with park resources. Map unit ages are constrained by relative soil chronostratigraphy, vertebrate and invertebrate fossils, and materials collected for dating control using radiogenic, luminescence, and cosmogenic radionuclide techniques. Associated topical studies examined connections between geology, surface water, and vegetation distribution and restoration.

California↗
USGS2019

Fluvial sedimentary history of Arlington Canyon, Channel Islands National Park, California

Arlington Canyon, in the northwest part of Santa Rosa Island, Channel Islands National Park, California, has been the setting for important scientific discoveries over the past half century, including the oldest human remains in North America, several vertebrate fossil sites, and purported evidence of a catastrophic extinction event at the end of the Pleistocene. The canyon is filled with alluvial sediments that date to between 16.4 and 1.1 ka (thousands of calibrated years before present), representing accumulation that occurred primarily in response to rising sea levels during the late Pleistocene and Holocene. The deposits are laterally discontinuous, exhibit a high degree of sedimentary complexity, and contain evidence of past climates and environments, including fossil bones, burned plant macrofossils, and invertebrate microfossils. Here, we show that it is critical to view the observations, data, and conclusions of scientific studies conducted in the canyon within this larger context so that localized facets of the spatially and temporally extensive alluvial deposits are not misinterpreted or misrepresented. By improving the baseline understanding of processes and drivers of sediment accumulation in Arlington Canyon, we hope to offer a solid foundation and better underpinning for future archeological, paleontological, and geochemical studies here and throughout the northern Channel Islands.

California↗
USGS2018

Quaternary sea-level history and the origin of the northernmost coastal aeolianites in the Americas: Channel Islands National Park, California, USA

Along most of the Pacific Coast of North America, sand dunes are dominantly silicate-rich. On the California Channel Islands, however, dunes are carbonate-rich, due to high productivity offshore and a lack of dilution by silicate minerals. Older sands on the Channel Islands contain enough carbonate to be cemented into aeolianite. Several generations of carbonate aeolianites are present on the California Channel Islands and represent the northernmost Quaternary coastal aeolianites on the Pacific Coast of North America. The oldest aeolianites on the islands may date to the early Pleistocene and thus far have only been found on Santa Cruz Island. Aeolianites with well-developed soils are found on both San Miguel Island and Santa Rosa Island and likely date to the middle Pleistocene. The youngest and best-dated aeolianites are located on San Miguel Island and Santa Rosa Island. These sediments were deposited during the late Pleistocene following the emergence of marine terraces that date to the last interglacial complex (~ 120,000 yr to ~ 80,000 yr). Based on radiocarbon and luminescence dating, the ages of these units correspond in time with marine isotope stages [MIS] 4, 3, and 2. Sea level was significantly lower than present during all three time periods. Reconstruction of insular paleogeography indicates that large areas to the north and northwest of the islands would have been exposed at these times, providing a ready source of carbonate-rich skeletal sands. These findings differ from a previously held concept that carbonate aeolianites are dominantly an interglacial phenomenon forming during high stands of sea. In contrast, our results are consistent with the findings of other investigators of the past decade who have reported evidence of glacial-age and interstadial-age aeolianites on coastlines of Australia and South Africa. They are also consistent with observations made by Darwin regarding the origin of aeolianites on the island of St. Helena, in the South Atlantic Ocean, more than a century and a half ago.

California↗
USGS2017

Oak habitat recovery on California's largest islands: Scenarios for the role of corvid seed dispersal

Seed dispersal by birds is central to the passive restoration of many tree communities. Reintroduction of extinct seed dispersers can therefore restore degraded forests and woodlands. To test this, we constructed a spatially explicit simulation model, parameterized with field data, to consider the effect of different seed dispersal scenarios on the extent of oak populations. We applied the model to two islands in California's Channel Islands National Park (USA), one of which has lost a key seed disperser. We used an ensemble modelling approach to simulate island scrub oak ( Quercus pacifica ) demography. The model was developed and trained to recreate known population changes over a 20-year period on 250-km 2 Santa Cruz Island, and incorporated acorn dispersal by island scrub-jays ( Aphelocoma insularis ), deer mice ( Peromyscus maniculatus ) and gravity, as well as seed predation. We applied the trained model to 215-km 2 Santa Rosa Island to examine how reintroducing island scrub-jays would affect the rate and pattern of oak population expansion. Oak habitat on Santa Rosa Island has been greatly reduced from its historical extent due to past grazing by introduced ungulates, the last of which were removed by 2011. Our simulation model predicts that a seed dispersal scenario including island scrub-jays would increase the extent of the island scrub oak population on Santa Rosa Island by 281% over 100 years, and by 544% over 200 years. Scenarios without jays would result in little expansion. Simulated long-distance seed dispersal by jays also facilitates establishment of discontinuous patches of oaks, and increases their elevational distribution. Synthesis and applications . Scenario planning provides powerful decision support for conservation managers. We used ensemble modelling of plant demographic and seed dispersal processes to investigate whether the reintroduction of seed dispersers could provide cost-effective means of achieving broader ecosystem restoration goals on California's second-largest island. The simulation model, extensively parameterized with field data, suggests that re-establishing the mutualism with seed-hoarding jays would accelerate the expansion of island scrub oak, which could benefit myriad species of conservation concern.

California↗
USGS2017

Late Quaternary sea-level history and the antiquity of mammoths ( Mammuthus exilis and Mammuthus columbi ), Channel Islands NationalPark, California, USA

Fossils of Columbian mammoths ( Mammuthus columbi ) and pygmy mammoths ( Mammuthus exilis ) have been reported from Channel Islands National Park, California. Most date to the last glacial period (Marine Isotope Stage [MIS] 2), but a tusk of M. exilis (or immature M. columbi ) was found in the lowest marine terrace of Santa Rosa Island. Uranium-series dating of corals yielded ages from 83.8 ± 0.6 ka to 78.6 ± 0.5 ka, correlating the terrace with MIS 5.1, a time of relatively high sea level. Mammoths likely immigrated to the islands by swimming during the glacial periods MIS 6 (~ 150 ka) or MIS 8 (~ 250 ka), when sea level was low and the island–mainland distance was minimal, as during MIS 2. Earliest mammoth immigration to the islands likely occurred late enough in the Quaternary that uplift of the islands and the mainland decreased the swimming distance to a range that could be accomplished by mammoths. Results challenge the hypothesis that climate change, vegetation change, and decreased land area from sea-level rise were the causes of mammoth extinction at the Pleistocene/Holocene boundary on the Channel Islands. Pre-MIS 2 mammoth populations would have experienced similar or even more dramatic changes at the MIS 6/5.5 transition.

California↗
USGS2014

Coastal tectonics on the eastern margin of the Pacific Rim: Late Quaternary sea-level history and uplift rates, Channel Islands National Park, California, USA

The Pacific Rim is a region where tectonic processes play a significant role in coastal landscape evolution. Coastal California, on the eastern margin of the Pacific Rm, is very active tectonically and geomorphic expressions of this include uplifted marine terraces. There have been, however, conflicting estimates of the rate of late Quaternary uplift of marine terraces in coastal California, particularly for the orthern Channel Islands. In the present study, the terraces on San Miguel Island and Santa Rosa Island were mapped and new age estimates were generated using uranium-series dating of fossil corals and amino acid geochronology of fossil mollusks. Results indicate that the 2nd terrace on both islands is ~120 ka and the 1st terrace on Santa Rosa Island is ~80 ka. These ages correspond to two global high-sea stands of the Last Interglacial complex, marine isotope stages (MIS) 5.5 and 51, respectively. The age estimates indicate that San Miguel Island and Santa Rosa Island have been tectonically uplifted at rates of 0.12e0.20 m/ka in the late Quaternary, similar to uplift rates inferred from previous studies on neighboring San Cruz Island. The newly estimated uplift rates for the northern Channel Islands are, however, an order of magnitude lower than a recent study that generated uplift rates from an offshore terrace dating to the Last Glacial period. The differences between the estimated uplift rates in the present study and the offshore study are explained by the magnitude of glacial isostatic adjustment (GIA) effects that were not known at the time of the earlier study. Set in the larger context of northeastern Pacific Rim tectonics, Channel Islands uplift rates are higher than those coastal localities on the margin of the East Pacific Rise spreading center, but slightly lower than those of most localities adjacent to the Cascadia subduction zone. The uplift rates reported here for the northern Channel Islands are similar to those reported for most other localities where strike-slip tectonics are dominant, but lower than localities where restraining bends (such as the Big Bend of the San Andreas Fault) result in crustal shortening.

California↗
USGS1988

Soils and vegetation of Santa Barbara Island, Channel Islands National Park, CA

The multifaceted development of an erosion surface on Santa Barbara Island, Channel Islands National Park, California, has led to this study of the relationship between soils and vegetation. A dry Mediterranean climate and past attempts at farming and introductions of alien species have led to vegetative degradation accompanied by both gully and surface erosion. Soil and vegetation analyses show this erosion to be in a location of transition. The soils are Typic Chromoxererts (Vertisol Order) with high clay, salinity, and sodium contents. The vegetation is ecotonal in nature, grading from a principally alien annual grassland with Avena fatua and Atriplex semibaccata to a shrub community dominated by the native Suaeda californica . Management toward revegetation and stabilization of this island ecosystem will be difficult with high clay, saline-sodic soils and disturbed vegetation.

California↗