The geologic history of fluvial systems on Santa Cruz Island (SCI) is complex, involving responses to both allogenic and autogenic forcings. During periods of low or lowering sea level, canyons on the island were eroded and sediment was transported off the island onto the exposed marine shelf. When sea level rose, streams aggraded, building a sedimentary wedge that progressed from the shelf upstream into the canyons. This cycle of erosion and aggradation in response to glacial–interglacial sea-level cycles was likely repeated numerous times during the Quaternary, although clear evidence of only the most recent cycle is present in the island’s alluvial sequences. Christy, Sauces, and Pozo Canyons contain thick packages of fine-grained sediments that were deposited as a result of the interaction between autogenic depositional processes and allogenic forcing of continuous base-level rise. Other canyons on the island either have little alluvial fill due to their steep gradients or are filled with coarse-grained, recent (likely late Holocene) alluvium that covers the older alluvial deposits. Differences in the nature and extent of the alluvial exposures on SCI relative to those on neighboring Santa Rosa Island reflect differences in the local topography, geology, and ranching histories of the 2 islands.

Although it is critical for survival of plants and animals, and for understanding prehistory of early humans, little work has been done on the stream hydrology of the California Channel Islands. In September 2014, August 2016, and October 2017, during the driest period of the year, park staff and volunteers mapped surface water on Santa Rosa Island, Channel Islands National Park, by walking drainages (2nd order and higher) and recording the location of surface water using consumer-grade Global Positioning System (GPS) units. In 2014, mappers hiked 293 km (182 miles) of stream channel in 19 major drainage basins and 7 lesser drainage basins. The hiking teams recorded 759 water features (pools and springs) and 67 km (42 miles) of surface water. The 2016 repeat mapping in Verde, Trancion, Arlington, and San Augustin canyons, the 4 wettest drainages in 2014, showed that surface water declined by 10.1%, 21.1%, and 34.2% for the first 3 canyons, respectively; surface water in San Augustin increased by 1.3% between 2014 and 2016. Repeat mapping in 2017 of Verde, Trancion, Arlington, San Augustin, and Water canyons showed an increase from 28.3% to 90.0% in surface water following an above-average rainfall year in 2016–2017. Results have important implications for plant and animal life that depend on water on Santa Rosa Island.

Marine terraces are common on the Pacific Coast of North America and record interglacial high-sea stands superimposed on either stable or tectonically rising crustal blocks. Despite many years of study of these landforms in southern California, little work on terraces has been conducted on the two smallest of the California Channel Islands, Santa Barbara Island (SBI) and Anacapa Island (ANA). Presented here are new field and laboratory data on the ages, paleontology, and sea level history of marine terraces of these two islands. On both islands, the lowest marine terraces have shoreline angle elevations of ∼11 m above sea level. Amino acid geochronology shows that terrace deposits on both islands host fossils of two ages, one group dating to the ∼120-ka high-sea stand and the other group likely dating to the ∼100-ka high-sea stand. A mix of fossil ages is consistent with the paleontology as well, with SBI in particular showing a faunal assemblage that includes both extralimital southern and southward-ranging species (inferred to be from the ∼120-ka high-sea stand) and extralimital northern and northward-ranging species (inferred to be from the ∼100-ka high-sea stand). Fossil mixing from these two high-sea stands supports the hypothesis that glacial isostatic adjustment (GIA) processes have left a strong imprint on the geologic record of sea level history in southern California. Nevertheless, the elevations of these terraces and that of a low terrace on Santa Cruz Island indicate that modeled GIA estimates of paleo-sea level for the peak of the last interglacial period at ∼120 ka could be too high. Future development of models of GIA effects on the Pacific Coast of North America will need to consider geologic records, such as those from SBI and ANA, in refining reconstructions of sea level history.

We determine spatial and temporal dynamics of chlorophyll for the Southern California Bight through analysis of 10 years of chlorophyll product derived from the Moderate Resolution Imaging Spectroradiometer on the Earth Observing System satellite Aqua (MODIS-AQUA). Concentrating on the Southern Channel Islands, we find an island mass effect associated with San Nicolas; that is, some chlorophyll originates near the island. This signal is most evident during the fall after the typical spring phytoplankton bloom subsides. In contrast, there is a relative dearth of chlorophyll around Santa Catalina Island, and its seasonal modulation corresponds to the spring bloom, implying that the dynamics are much simpler for this island. Previous studies of temperature in the inner Southern California Bight near Santa Catalina indicate that a simple one-dimensional model of temperature diffusion explains well the seasonal and depth temperature modulations found there. We couple the temperature-derived vertical diffusion coefficient with nitrate measurements from California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises to make a simple one-dimensional model relating chlorophyll, insolation, and nitrate for Santa Catalina.

Silvetia compressa is a common rocky intertidal fucoid that plays an important role in the community and has experienced widespread declines throughout California. The causes of these declines are unknown, but sea surface temperature (SST) is considered one of the dominant factors affecting intertidal algae. The 2015–2016 El Niño introduced anomalously high SSTs to southern California, which may have impacted rocky intertidal species. This study investigates temporal changes in abundance of S. compressa with respect to SST at 4 sites on San Clemente Island (SCI), California, from 2012 to 2016. Point-intercept data were used to quantify percent cover during biannual intertidal surveys. To correlate SST with changes in S. compressa percent cover, we utilized SST data collected approximately 50 km southeast of SCI from the National Data Buoy Center. Our results indicated significant declines in S. compressa in spring 2015 across all 4 sites following SST anomalies that began in 2014. Linear regression between S. compressa percent cover and the previous year’s maximum SSTs showed a significant negative relationship, indicating that reduced abundance of S. compressa was moderately associated with elevated SSTs.

The vegetation of Santa Catalina Island has been significantly transformed through a history of introduction of exotic plant species and disturbance by large introduced herbivores. Many of these disturbances have been reduced in recent decades, using measures such as carefully controlling the number of bison and removing cattle, sheep, feral pigs, and goats. The success of subsequent vegetation restoration actions depends on the choice of the right plant community for a location, which may not be obvious for an island with extensive areas dominated by exotic species. Environmental niche modeling is an approach to re-create the spatial distribution of habitat types for such a purpose. Such models, however, often require both presence and absence data to be meaningful, while in this scenario absence is misleading because it may reflect a long history of disturbance. Maximum entropy modeling is a technique to model species distributions with presence-only data that has been shown to produce accurate results. We used this modeling tool to model the environmental niche for distinct vegetation types, conceptualized as potential natural vegetation, on Catalina Island as a means to predict locations where restoration actions would be most successful and to predict potential natural vegetation prior to anthropogenic disturbance. Using an existing vegetation map, we extracted random points from within the polygons defining each native vegetation type. We then modeled the habitat suitability for each habitat using high-resolution environmental data that included elevation, aspect, hillshade, northeastness, slope, solar radiation, and topographic wetness index. The resulting models were combined to produce a map of potential natural vegetation. A 1977 map of potential natural vegetation included 4 vegetation types (woodland, chaparral, scrub, and grassland) to which we compared our results. Our new model of potential natural vegetation has high spatial complexity and high resolution. It also shows naturalistic responses to topography that are consistent with the broad patterns mapped in 1977 while providing fine-scale resolution to inform restoration efforts.

Kelp forest communities are highly variable over space and time. Despite this complexity it has been suggested that kelp forest communities can be classified into one of 2 states: kelp dominated or sea urchin dominated. It has been further hypothesized that these represent “alternate stable states” because a site can remain in either of these states for decades before some perturbation causes a rapid shift to the other state. Our research group has maintained a subtidal community monitoring program for 38 years at San Nicolas Island consisting of twice-annual scuba-based surveys at 6 sites distributed within 4 regions around the island. Three types of perturbations are thought to be relevant to subtidal community dynamics at San Nicolas: (1) physical disturbances in the form of major storm and El Niño/ Southern Oscillation (ENSO) events; (2) invertebrate diseases, which periodically decimate urchin populations; and (3) the reintroduction and subsequent increase of sea otters (Enhydra lutris nereis). These 3 perturbations differ in spatial and temporal specificity; physical disturbances and disease outbreaks occur periodically and could affect all 4 regions, while sea otter predation has been concentrated primarily at the West End sites over the last 15 years. The different types of perturbations and the duration of the time series at the kelp forests at San Nicolas make the data set ideal for testing the “alternate stable state” hypothesis. We use nonmetric multidimensional scaling (NMDS) to examine spatial and temporal patterns of community similarity at the 4 regions. In particular, we evaluate support for the existence of stable states, which are represented on NMDS plots as distinct spatial clusters. Community dynamics at each site approximated a biased random walk in NMDS space, with one or more basins of attraction and occasional jumps between basins. We found evidence for alternative stable states at some sites, and we show that transitions from one stable state to another may be influenced by interactions between multiple perturbations.

Prisoners Harbor on Santa Cruz Island, California, formerly supported a 5-ha wetland and riparian system, the largest on the California Channel Islands. During the late 1800s ranchers filled in about half of the wetland area in order to support ranching activities. They also rerouted the stream channel to the canyon edge and built an earthen berm along its west bank, which disconnected the stream from its floodplain. The National Park Service developed a wetland and riparian restoration design for Prisoners Harbor based on topographic and hydrologic analyses and on vegetation community depth-to-water-table relationships developed from neighboring reference wetlands. In 2011 Channel Islands National Park and The Nature Conservancy restored 1.25 ha of coastal wetlands by removing artificial fill and the earthen berm. Postproject vegetation monitoring during 2012 to 2016 showed increased abundance of 3 of the 8 herbaceous planted wetland species and declines in target invasive species. Severe drought conditions during this window likely influenced vegetation abundance. Postrestoration hydrologic monitoring showed that the restored marsh met the federal wetland hydrology standard only twice: once in late 2011 before the drought began and then again in January–September 2017. An exceptionally large swell and high tide during winter 2015/16 resulted in saltwater flooding of the site; salinity returned to more typical values only slowly after this event. Expansion of wetland species, even during a historic drought and atypical seawater intrusion, suggests that this evidence-based approach to restoration design will result in functional coastal wetland habitat as more typical precipitation levels return. However, we emphasize the need for aggressive control of nonnative plants until native plant cover is well established.

The 3 islets of Anacapa Island, with a combined area of 1.1 mi² (2.9 km²), lie 13 mi (20 km) off the coast of southern California. Historically, each of Anacapa’s islets has been subjected to periodic grazing by sheep, and the eastern islet has also had a sizeable population of introduced rabbits. In spite of these past perturbations, the recovery of the island’s vegetation has been remarkable since sheep removal in 1937. Despite its small size, Anacapa Island supports a surprising diversity of vascular plants, with nearly 200 native taxa from 50 plant families. Twenty-one of these native taxa are restricted to the California Islands; one annual species of Malacothrix occurs as a narrow endemic found only on Middle Anacapa Island, while another annual subspecies of Malacothrix is known only from West and East Anacapa. The floral diversity of this island has apparently been influenced by its close proximity to the mainland and other larger islands and by its diverse topography. Anacapa Island supports a slightly larger native flora than San Miguel Island, which is about 13 times larger and is located about 50 mi (80 km) to the west. The Anacapa native flora is more than twice the size of that found on Santa Barbara Island, which has almost the same area as Anacapa Island but is located approximately 62 mi (100 km) to the southeast. Even though botanical exploration on Anacapa began in 1889, the current work represents the first complete enumeration of the island’s flora.

In the last 3 years, significant advances have occurred in our knowledge of the flora of the northern Baja California Pacific Islands. The availability of herbarium specimen data has been significantly increased, and 2 expeditions were undertaken to 7 of the 8 islands in 2015 and 2016. These events have resulted in a wealth of new plant records from the islands, which are here reported with updated taxonomy for the archipelago. The results include 586 vascular plant taxa on the Baja California Northern Pacific Islands; 118 taxa were new, and 54 previously reported taxa were vouchered. The checklists include the nativity of the taxa and highlight new records discovered through fieldwork, as well as those that were hidden in herbaria until now. The declaration of these islands as a new UNESCO Biosphere Reserve in late 2016 makes these new records of particular conservation importance, bettering our baseline understanding of these islands’ ecosystems.

Spore-bearing and seed-bearing plants differ in their ability to colonize islands from mainland sources. To assess the importance of these differences, we investigated patterns of species richness and species composition for the native bryophyte, fern, and seed plant floras of the California Channel Islands. Native richness was regressed against island area, maximum elevation, distance to mainland, distance to nearest propagule source along prevailing wind trajectories, and latitude for the 3 plant groups. Ordinations, Mantel tests, randomization tests, and an analysis partitioning beta diversity into turnover and nestedness components were used to identify similarities and differences in species composition across the 3 groups. Patterns of species richness were mostly consistent across the 3 groups, with island area and maximum elevation being much more important than distance to mainland or distance from nearest propagule source. Patterns of species composition were also generally consistent across the 3 groups. The 3 floras exhibit similar patterns of compositional change across the archipelago and these patterns are not driven by geographic distance among islands. Island area and maximum elevation were significant predictors of compositional change, but the 2 distance metrics were not. The seed plant flora exhibited strong turnover between the 4 northern and 4 southern islands, while the bryophyte flora exhibited southern islands floras nested within those of northern islands. We interpret these findings as suggesting that ecological filtering is more important than dispersal limitation for developing both seed-bearing and spore-bearing plants on the islands.

The Catalina Island Conservancy manages over 22,000 acres of coastal (California) sage scrub (CSS) habitat off the coast of Southern California, including much of the infrastructure, roads, and recreation associated with habitat disturbance. Restoration trials were initiated to establish best management practices for roadside and disturbed site revegetation under local site conditions. Site treatments compared excavated native subsoil and surface soil (±20 cm) reapplication practices with and without seed augmentation. Evaluation of native and nonnative germinants indicated that salvaged surface soil alone may not be sufficient to restore native cover. Seeding improved native cover and reduced establishment of nonnative species on unirrigated sites. Evaluation of water potential of seedlings indicated that high-frequency irrigation may favor establishment of nonnative annual grasses. Most compelling for land managers is the indication that CSS habitats may contain a significant nonnative seed bank in spite of the composition of aboveground vegetation, such that disturbance may facilitate habitat-type conversion without seed augmentation or weed control.

California Channel Island buckwheats are important components of scrub communities on the Channel Islands. A long history of overgrazing by introduced herbivores on San Clemente Island has contributed to scrub vegetation loss and population declines in 2 endemic island taxa, Eriogonum giganteum var. formosum and E. grande var. grande. Since herbivore removal, Eriogonum species, which are early colonizers of disturbed habitats, have been increasing across the island. These increases are thought to facilitate further recovery of the native flora because the shrubs act as nurse plants and improve the soil profile for other native species.

The California Channel Islands are unique relative to other island chains due to their close proximity to the California mainland and the fact that individual islands, or groups of islands, vary in their distance to the mainland and other islands. This orientation raises questions about whether island taxa with widespread distributions form cohesive evolutionary units, or if they are actually composed of several distinct evolutionary entities, either derived from independent mainland-to-island colonization events or divergence due to prolonged allopatric isolation. The 4 northern islands are clustered in a line (6–8 km separation among islands), while the 4 southern islands are widely spaced (34–45 km separation among islands), which should impact the amount of gene flow and genetic connectivity among islands. We used nuclear microsatellite markers to examine the genetic structure and cohesion of 2 island shrubs, Acmispon dendroideus and A. argophyllus, which are widely distributed across the California Channel Islands. Both focal species contain varieties with multi-island distributions, with A. dendroideus exhibiting a greater distribution on the northern islands and A. argophyllus exhibiting a greater distribution on the southern islands. Substantial genetic divergence was observed for 2 single-island endemic varieties, A. dendroideus var. traskiae and A. agrophyllus var. niveus, confirming that allopatric isolation can lead to genetic divergence. The widespread Acmispon dendroideus var. dendroideus and single-island endemic A. dendroideus var. veatchii formed a cohesive evolutionary group that spans all 4 northern islands and 1 southern island, Santa Catalina, indicating that the northern and southern islands have been genetically linked in the past but do not display evidence of contemporary gene flow. In contrast, widespread A. argophyllus var. argenteus was composed of moderately distinct genetic groups on each of the 4 southern islands, with no evidence of recent gene flow among islands. These results demonstrate that isolation among islands has led to significant divergence among the southern islands, but that the commonly recognized split between northern and southern islands does not impact all taxa equally.

Quercus tomentella (island oak) is an endemic species that plays a key functional role in Channel Island ecosystems. Growing in groves on highland ridges, Q. tomentella captures fog and increases water inputs, stabilizes soils, and provides habitat for flora and fauna. This cloud forest system has been impacted by a long history of ranching, and restoration efforts are underway that include erosion control, leaf litter capture, fog capture, and reforestation. To inform retoration efforts, we explored tree regeneration and the potential for Q. tomentella grove expansion on Santa Rosa Island. We delineated current and historic groves at Black Mountain by comparing stand maps from 1989 and aerial photographs from 1994 and 2015. We evaluated regeneration in the outlying areas by recording the location, diameter at breast height, number of trunks, height class, percent crown mortality, nurse plant species (if present), and reproductive status for all 4355 outlying seedlings, saplings, and mature trees. We defined outliers as individuals that were 15 m outside of the canopy of island oak groves. There are 14 groves at Black Mountain, and grove size expanded by an average of 36.9% (SD 18.5%) between 1994 and 2015. Nurse plants correlated positively with outlier tree height and reduced percent crown mortality. This effect is potentially due to increased fog drip from nurse plant species such as Quercus pacifica (island scrub oak), Heteromeles arbutifolia (toyon), and Baccharis pilularis (coyote brush). These results indicate that Q. tomentella is regenerating and that nurse plants can serve as catalysts for ecosystem restoration.

The absence of herbivores from certain environments may select for plants that are less defended and more palatable compared to plants in similar environments that are exposed to herbivory. This potential loss of defenses becomes especially important when exotic herbivores are introduced to islands that historically lack such organisms, potentially resulting in negative effects on native island ecosystems. To test the hypothesis that island plants have reduced defensive traits, we measured structural defenses and palatability of 10 taxonomic pairs from contrasting island and mainland environments. Our study compares plants from Santa Catalina Island, California—which has a long history without large native herbivores followed by more recent human-caused introductions—to the adjacent southern California mainland where ungulate herbivores are native and common. Our results suggest that island plants have reduced structural defenses and are more preferred by herbivores compared to their mainland plant relatives. These patterns are likely driven by selection on plant traits in the unique and insular island environment. Reduced defenses and increased palatability of island plant species should be considered when developing management strategies for island ecosystems that historically lack native ungulate herbivores.

A combination of overgrazing and exotic species introduction has led to the degradation of habitats worldwide. It is often unclear whether removal of exotic ungulates will lead to the natural reestablishment of native plant communities without further management inputs. I describe here my return to sites on Santa Cruz Island, California, 12 years after initial sampling in order to gain a long-term view on native shrub reestablishment into exotic grasslands after exotic grazer removal. Santa Cruz Island was grazed by feral sheep and cattle for over a century; these exotic grazers were removed in the late 1980s and feral pigs were removed in 2005–2006. I resampled 5 sites on south-facing slopes in the Central Valley of the island to quantify native shrub cover, density, and size. Previous data suggested that one species, Eriogonum arborescens, would be able to naturally recruit in exotic grass–dominated areas. Native shrubs have shown a modest increase in cover over time, although more striking was a sharp increase in the amount of dead shrub cover and density. Recruitment events during high rainfall years probably led to the slight increase in Eriogonum cover between sampling periods. Recent drought periods, however, have probably increased mortality and otherwise slowed shrub reestablishment in these arid sites.

Ecosystem restoration efforts have been ongoing on the Channel Islands of California since the 1980s. Although these island ecosystems evolved without ungulate grazers, large nonnative grazers, including sheep, cattle, feral pigs, deer, and elk, were present on the islands for over 160 years. Intensive grazing led to reductions in the extent of woody vegetation, increases in the area of grassland and bare ground, and widespread landsliding and gully erosion. This study focuses on Santa Rosa Island, the second largest (215.3 km²) island in Channel Islands National Park. After the park was created in 1980, the National Park Service progressively removed nonnative grazers to facilitate the restoration of native vegetation and the wildlife communities they support. We constructed a time series (1989 to 2015) of Landsat TM5 and Landsat 7 ETM+ images to evaluate large-scale and long-term vegetation change in response to grazer removal on Santa Rosa Island. We also evaluated the influence of slope percent, which can be an indicator of past grazing accessibility, on ecosystem recovery. Results indicate that removing nonnative grazers led to passive restoration of 42.1 km2 of scrub, chaparral, and woodland vegetation. In contrast, the area of grassland vegetation decreased by 31.2 km2 and bare ground decreased by 12.0 km². The extent of scrub and woodland vegetation recovery was greater on gentle and moderate slopes compared to steep slopes, indicating that terrain does influence passive restoration. Despite changes in vegetation cover, 5.4 km2 has remained bare. Much of the bare ground is on ridgelines that were denuded down to the bedrock or regolith. Active restoration will be necessary on bare ridgelines, such as erosion control, fog capture, and oak woodland reforestation.

The land snails and slugs have the highest level of endemism among all major animal groups on the California Channel Islands, with nearly 75% of the native terrestrial species confined to one or more of the 8 islands. In spite of this endemism, and in spite of the rarity of some species, the snails and slugs are one of the most poorly known groups. We present the first comprehensive overview of the land mollusk fauna of the Channel Islands, along with the results of recent intensive inventory studies. Surveys on San Clemente Island have increased the number of land mollusk species known from that island by 50%, and a single survey trip to Santa Rosa Island more than doubled the number of species known on that island. More additions to the land snail and slug fauna are certain for the poorly surveyed northern Channel Islands. This new information has provided insight into trends in species diversity and biogeographic patterns, with marked differences in species composition between the northern and southern islands. Our surveys to date suggest a strong link between the recovery of native vegetation on the islands and the population status of land snails and slugs, with substantially larger numbers of native mollusks on those islands that have been free of nonnative mammals the longest. Survey work is continuing, but it is clear that some very rare endemic snails and slugs on the islands merit specific management attention.

Wild bees provide the essential ecosystem service of pollination, which may be particularly important in island systems that host rare and endangered plants. Identifying and protecting nesting habitat of wild bees is critical for successfully conserving these pollinators and their pollination services, but characterization and delimitation of nesting habitat receives relatively little attention in the literature compared to description of floral interactions. Such data on wild bee nesting is necessary for creating effective conservation strategies that benefit the stability of ecosystem services, as well as promote the populations of both pollinators and plants. On San Clemente Island, we identified the locations of 50 bee nest sites. Bees from 12 sites were collected and identified as Diadasia bituberculata (n = 9), D. opuntiae (n = 2), and Anthidium collectum (n = 1). We characterized sites by vegetation cover and soil type: half (54%) of the sites were found in maritime desert scrub–prickly pear phase vegetation, and most (82%) were associated with loam-type soil. Here we provide the first descriptions of ground-nesting bee habitats on San Clemente Island and suggest that conservation of bee nesting habitat could be incorporated into existing avian and plant conservation management efforts in these shared habitats.

The Argentine ant (Linepithema humile) is a widespread and abundant introduced species that disrupts ecosystems throughout its introduced range. This invader was inadvertently introduced to Santa Catalina, San Clemente, Santa Cruz, and San Nicolas Islands at various points during the past century but currently appears to be absent from the remaining Channel Islands. Multiple spatially disjunct infestations on each invaded island individually range in size from <500 m² to >427 ha and encompass a variety of habitats, including large areas that are entirely dominated by native perennial vegetation. The existence of multiple infestations on individual islands suggests that inadvertent introduction by humans serves as an important within-island dispersal mechanism. Multiyear surveys of individual infestations on San Clemente Island and Santa Cruz Island reveal approximately radial patterns of expansion (as a result of colony budding) away from the edge of each infestation. Rates of spread by budding on San Clemente Island range from 10 m/year to 57 m/year and are comparable to those on mainland California. Given the documented effects of Argentine ant invasions on Santa Cruz Island, the continued spread of the Argentine ant on the Channel Islands represents a serious environmental concern. Eradication programs underway on San Clemente and Santa Cruz Islands will hopefully result in island-wide elimination of this detrimental invader.

The Argentine ant, Linepithema humile (Mayr), is a highly invasive ant species that has spread into urban, agricultural, and natural areas worldwide. The pervasive expansion of this species is detrimental both ecologically and economically, resulting in the allocation of vast amounts of resources for control. New efforts are underway to control the Argentine ant in ecologically sensitive habitats, such as those on the California Channel Islands. We tested the efficacy of thiamethoxam liquid bait at a concentration of 6 ppm on San Clemente Island, California, where the Argentine ant has spread into natural areas hosting protected endemic species. Applied by hand, helicopter, and ATV, hygroscopic polyacrylamide beads were used as a bait matrix to deliver the liquid bait (thiamethoxam and sucrose) for Argentine ant infestations at 5 sites (totaling 177 ha) on San Clemente Island. Treatments reduced the number of monitoring points at which the Argentine ant was detected 1 year posttreatment (17.91% vs. 3.65%), suggesting that these methods are a promising conservation tool. Continued monitoring to detect remaining infestations will be necessary for eventual eradication of the Argentine ant from San Clemente Island.

An understanding of how past conditions have shaped present-day ecological patterns and trends is critical to science-based conservation management. Unfortunately, the records, specimens, and objects historical ecologists need to help generate that understanding are often lacking. And because of a general underinvestment by society in systematic collection and museum curation, future historical ecologists may be similarly limited in their ability to investigate conditions regarding our present day. Given the importance of historical data and materials in contemporary conservation decision-making, we suggest it is incumbent upon resource managers and scientists to ask whether additional research efforts are needed to document past and present conditions of the places and resources of their interest. Here, we discuss how such an inquiry was applied to the terrestrial and nearshore environments of Santa Cruz Island, California, USA. The island harbors numerous endemic taxa, important archaeological and fossil sites, and rich cultural significance. It also has undergone dramatic and ongoing alteration due to past and present human activities. We describe an interdisciplinary effort to identify information gaps regarding past and present conditions of the island. In many cases, filling those gaps will require a research focus on a broader geography and suite of resources, including the archipelago in which the island sits and mainland “sister sites.” An initiative to improve collection and retention of priority information could be a basis of interdisciplinary and multi-institutional collaboration and could be designed to foster environmental education and citizen science programs that engage the next generation of conservationists. An outcome of this initiative would be an archive of materials and data to inform the historical ecologists and conservationists of the future, and to help conservationists today ensure that the resources they deem most important will be stewarded successfully into that future.

Santa Cruz Island contains a remarkable array of cultural and biological resources and a rich tradition of research across the social and biological sciences and humanities. Given dramatic changes in climate forecast in the coming decades of the Anthropocene, however, many questions remain about the sustainability and future of island ecosystems and cultural resources. Here, we focus on a new interdisciplinary initiative, Island Rediscovery (IR), that was the subject of 2 recent workshops. Drawing on a variety of disciplines and approaches, IR seeks to utilize research on Santa Cruz Island's past and present to help better prepare for the future and plan for forecast change, an approach we call horizon scanning. Our focus is on archaeology, history, and paleobiology, 3 disciplines that offer deep historical perspectives critical to understanding modern ecosystems and preparing for future variability. We outline the potential of deep historical research, offer core questions that can guide future work, and document the need for a large synthetic database and digitization effort. By integrating the historical and biological sciences, the historical ecological approach of IR offers a new framework for managing the resources of the California Islands by providing baselines and context for management, documenting the range of ecological variability through deep time, and helping establish desired future conditions.

Historical marine ecology provides information on past ocean conditions and community structure that can inform current conservation and management. In an era of rapid global ocean changes, it is critical that managers and scientists ensure sufficient documentation of past and present conditions of resources they manage or study. Documenting, archiving, and preserving historic and contemporary data will provide their colleagues in the future with more information to make robust science-based management decisions. Using a workshop approach, we identified research and archiving priorities to enhance documentation of the past and present conditions of coastal and marine ecosystems of the northern Channel Islands in California. We identified a variety of historical data types (e.g., archeological data, oral histories, environmental records, imagery) that should be preserved and analyzed to better understand past coastal and marine ecosystems around the northern Channel Islands. Continuing with long-term monitoring programs is also important for establishing baselines to inform contemporary management decisions and compare with future conditions. Herein, we underscore the role that individual scientists and managers working in the northern Channel Islands must play in documenting their work, archiving data, and preserving specimens in museums and institutions. Our case study for the northern Channel Islands provides a guide for how scientists should be documenting past and present conditions for marine resources around the world. Robust documentation of such conditions will give future scientists, managers, and other stakeholders the information needed to navigate what are sure to be increasingly complex management challenges.

Historical ecological research provides valuable insights for contemporary conservation management. Gaps in historical records, however, can limit the utility of that research. Future conservationists may therefore find themselves disadvantaged by the current societal trend of underinvestment in systematic collection of museum specimens and natural history information. To reduce that risk, we asked what managers and scientists could do today to better document the past and present conditions of Santa Cruz Island, California, as a means to improve both contemporary and future conservation. We focused our inquiry on the island's terrestrial fauna, which includes numerous taxa of conservation concern. Here we present recommendations for research and collection that will enhance not only the understanding of past and present ecological conditions on the island but also the records that will be accessible to future historical ecologists.

Climate changes are predicted to drive changes in plant species composition and vegetation cover around the world. Preserved specimens and other botanical information that we gather today—a period future practitioners may look back on as an early stage of modern anthropogenic climate change—will be of value to conservation managers and conservation biologists in the decades and centuries ahead. Here, we present suggestions for the systematic collection, long-term curation (in museums, herbaria, and other research institutions), and maintenance of plant specimens, along with associated data and analyses on the plants and vegetation present today and in the past. The primary aim of this systematic survey is to provide information of high value to conservation researchers and managers both in the near term (the next several years) and through the century to come. Such a systematic survey would build on a strong foundation of research and adaptive management on the island. It would fill gaps in less well-studied groups of organisms and identify environmental, ecological, and cultural factors related to current patterns of distribution. It would also archive previously collected data, photographs, and other materials which would otherwise gradually degrade and become inaccessible. As a case study, we use Santa Cruz Island, California, which is managed for conservation. We are confident that the same approach may be applied to other lands and waters around the world. We argue that there is a particular need to collect and archive herbarium specimens and seeds from today's populations, activities largely overlooked in recent decades. We encourage conservation researchers and managers to consider what information will be most important for future managers and to help launch studies, monitoring programs, and collections to prepare their successors for success.

After nearly 2 centuries of being negatively impacted, primarily by introduced mainland vertebrates, the unique flora and vegetation of the Islands of the Californias archipelago have been severely degraded. The botanical conservation challenges that lie ahead include the near extinction or extirpation of rare, endemic, and even common plant taxa; invasion of nonnative plants; near loss of unique island vegetation communities; and the degradation of a host of sites. These challenges are too large for any one entity to remedy alone. Many of the botanical resources impacted are found on multiple islands and cross political boundaries. The Islands of the Californias managers and their mainland partners have formalized a binational collaboration, the Islas de las Californias, Colaboración Botánica, or Islands of the Californias Botanical Collaborative (ICBC), to address these challenges more effectively and efficiently and thus achieve greater conservation success. The ICBC has identified and prioritized challenges in botanical resource management, taken actions to recover plant populations at risk and prevent future extinctions, developed tools to evaluate plant reintroductions, implemented quarterly meetings to share professional experiences, begun to develop tools for information and data sharing, and leveraged multi-island efforts for botanical resources funding. Herein we present our rationale for this collaborative and detail our progress toward creating archipelago-wide groups comprising the Invasive Plant Management Network, Plant Extinction Prevention Program, Native Plant Restoration Program, Integrated Biodiversity Information System, and Work Share Program.

In 2013, retired Park Ranger Mike Hill proposed writing the administrative history of the National Park Service (NPS) on San Miguel Island. An administrative history is the agency history of the NPS at a particular park, or in this case, on a particular island. Toward that end, 5 of the park rangers who have served as San Miguel Island Ranger gathered on that island in November 2013, along with former Superintendent Bill Ehorn and Chief of Cultural Resources Ann Huston. They reflected on years spent on San Miguel and recorded oral history interviews about those times.

The National Park Service (NPS) purchased Santa Rosa Island from private landowners Vail & Vickers in 1986. Immediately following the purchase, NPS personnel stated that they and the former landowners were negotiating a 5- to 10-year phaseout of cattle ranching and hunting of introduced deer and elk. Later, NPS staff stated that the former landowners had a 25-year right to presale land uses. This unsubstantiated “right” became the justification for the NPS issuing a series of permits that continued the operations of the former landowner. Over time, questions arose regarding the environmental impacts of the cattle, deer, and elk on Santa Rosa Island's natural and archeological resources and the restricted public use of the island. Approximately 10 years after purchasing the island, the National Park Service was sued by an environmental group. Vail & Vickers countersued. The litigation brought to light the written documents associated with the purchase of the island. The court cases were settled through a voluntary agreement which directed a rapid end to grazing of cattle and a phased reduction of deer and elk. This paper examines the written documents from 1979 to 1987, which is the period contemporaneous to the establishment of Channel Islands National Park, the sale of Santa Rosa Island, and the initiation of island management by the National Park Service. Later documents and statements will be compared to the contemporaneous documents to better understand the controversies, public perceptions, and lawsuits.

Eradication and maintenance management of island invasive species have long histories, and incremental improvements of existing technologies plus occasional novel approaches have led to more challenging targets and increased success rates in certain categories. Many nonnative mammals have been eradicated from islands, as have several nonnative birds, insects, and plants. Hundreds of rat populations have been eliminated, with a success rate over 80%, and islands over 10,000 ha are now feasible targets. Mouse eradication has proven more challenging, but aerial broadcast of anticoagulant toxins has led to increased success. Carnivore eradication—especially of feral housecats and foxes—has been frequently attempted with a recent success rate over 90%. Eradication of herbivores—primarily goats, rabbits, wild boar, and boar/pig hybrids—has been attempted almost 200 times, with a success rate over 90%. Trends in mammal eradication include more frequent attempts and higher success rates on larger islands and inhabited islands, as well as attempts targeting multiple invasive species. Documented conservation gains from island mammal eradications are numerous. For insects, about two-thirds of some 50 island attempts have succeeded, and most targeted agricultural pests. No summary statistics exist on island plant eradications, but several small infestations have been eradicated. Several insect and plant island invaders have been maintained at low densities by biological control, and plants have been controlled short of eradication by herbicides, often combined with physical or mechanical means. Failures in both eradication and maintenance management on islands often result from insufficient long-term commitment of resources. Excitement and controversy abound over the prospect that new techniques relying on molecular genetic tools—especially RNA-guided gene drives—may permit eradication or maintenance management of nonnative invaders in situations that have previously appeared extremely difficult or infeasible. Island populations of invertebrates, small mammals, and some plants are particularly propitious targets.

Invasive alien species represent one of the greatest threats to island ecosystems and the unique species that inhabit them. In many instances, eradication or control programs for invasive alien species have effectively curtailed the ongoing loss of biodiversity on islands. Prevention is a more proactive and cost-effective approach, however, and is an emerging global priority in the conservation of island ecosystems. Island biosecurity programs attempt to prevent the introduction and establishment of invasive alien species on islands and dictate actions when an invasive species is detected. Targeted and robust collaboration efforts among the global island community on biosecurity advances and challenges can strengthen and improve local biosecurity programs. In this paper we review the principal tenets of island biosecurity—prevention, detection, and response—using case studies of current island biosecurity programs from New Zealand, Chile, Mexico, the United States, and Canada. Systematic evaluations of biosecurity activities are necessary to ensure that programs are effective and relevant. Key priority actions for the future include strengthening global collaboration on biosecurity through holding annual meetings, sharing resources online, leveraging funding opportunities, and forming working groups that will be engaged in improving critically important but under-resourced biosecurity programs.