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The California Channel Islands comprise the eight major islands off the coast of southern California between Point Conception and the Mexican border. The eight islands are divided into two major groups: (1) the Northern Channel Islands of San Miguel, Santa Rosa, Santa Cruz, and Anacapa; and (2) the Southern Channel Islands of Santa Barbara, San Nicolas, Santa Catalina, and San Clemente. This chapter provides an overview of flora and vegetation of the California Channel Islands, describing plant communities such as scrub vegetation, chaparral, grasslands, woodland and forest, and vegetation in freshwater and coastal wetlands. It also discusses vegetation mapping, classification, and restoration; invasive plant mapping and control; rare plant surveys; and monitoring and protection efforts.

Due to their isolation, insularity, and lower biodiversity, the islands of Alta and Baja California have often been perceived as marginal habitat for humans compared to the adjacent mainland. Recent archaeological work, however, has revealed a deep history of sustained human settlement on many of the islands from the Terminal Pleistocene to the present, where large Native American populations had complex economies, sophisticated maritime technologies, and elaborate material cultures. With modern restoration efforts, the native vegetation, fisheries, and hydrology of the islands is recovering, raising questions about the marginality of the islands prior to European contact. This chapter draws from archaeological and ecological data to argue that the California Islands were optimal habitat for humans, with ample resources, both marine and terrestrial.

Until recently, with a few exceptions, California Islands were believed to be relatively impoverished in high-quality materials for making stone tools. This chapter summarizes the distributions of known mineral resources on the islands, including numerous sources identified during recent geoarchaeology surveys. For islands occupied since the Terminal Pleistocene, the availability of such resources may have changed significantly through time due to sea level rise and coastal erosion. There is spatial variability in the distribution of mineral resources, but we show that such resources were relatively abundant on many of California's islands. This has implications for understanding the antiquity of initial colonization of the islands, the development of exchange networks, and the marginality of island mineral resources.

If the California Islands were marginal environments for the indigenous people who occupied them, human population densities on the islands should be significantly lower than the adjacent mainland coast. Reconstructing population densities at particular times in the past is fraught with methodological difficulties, but data from site sizes and densities, radiocarbon date distributions, and mission records give no indication that island population densities were significantly lower than along the coastal mainland. Population density measures provide little evidence of environmental marginality on the Northern Channel Islands. Human population densities on islands further south may have been lower than the northern islands, but do not appear to have been significantly different than the adjacent mainland coast.

The California Islands provide a case study that suggests that historical depictions of many islands as marginal environments for hunter-gatherers have been exaggerated by the ecological effects of the introduction of exotic plants and animals, historically or prehistorically. The perception of island marginality is traditionally based on variables ranging from island size to remoteness, isolation, and limited resources. Located near a continent, the California Islands are neither remote nor isolated, and they now appear to have been richer in plant foods, marine resources, minerals, fuel, and freshwater, than previously believed. We discuss these issues and explore the implications for other islands around the world where similar transformations have affected views about their marginality for human settlement and sustainability.