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This chapter presents analyses that suggest increasing levels of invasion will be observed with increasing climate change, and that invasions of species from far away will increase disproportionately. It suggests that climate change will require us to reconsider our attitudes to the distinction between native and non-native species, because many species are only expected to survive climate change by establishing in new regions, outside their historical ranges.

Non-native species are widespread and abundant in California grasslands. This chapter provides an overview of the nature of these invaders, their distribution within California, factors influencing their abundance, and their impacts in the grassland ecosystem. It also reviews the impacts of plant pathogens in California grassland. Evidence suggests that pathogens may influence and mediate interactions between native and non-native plant species.

This chapter considers movement of species over time. Many land managers and ecologists consider invasive species to be the most important factor in disrupting "natural" ecosystems today, at least in North America. This chapter takes a historical approach to the process of species range extensions beginning with changes in the absence of human vectors, then considering the specifically human role in disseminating species world-wide. Human-mediated species' range extensions are ancient in many parts of the world so that what we might think of as "natural" may also have a human aspect. Using examples of range extensions of plants, animals, and disease-causing organisms, the discussion offers cautionary tales of species that have been introduced on purpose or inadvertently and have later caused severe disruptions to native ecosystems, as well as more positive examples of cultural landscapes in which non-native species are fully integrated into diverse and functional ecosystems. Comparing change over time in species diversity and importance may show unexpected patterns, such as the increase in both native and non-native plant species at the same sites in England. Historical studies also indicate that removal of the exotics may not lead to reestablishment of the native flora. Integration of some non-native species into a new ecosystem may eventually be more or less complete.

Restoration is the complex set of efforts to reverse or mitigate effects of human activity on the landscape. Restoration of California grasslands is now under way at many sites. This chapter discusses grassland restoration efforts, paying special attention to desired species attention and effects of past human activities. It first discusses the constraints on restoration efforts, such as invasive non-native species, land use, viral diseases, road construction, fire, and grazing. The chapter then examines the goals, implementation, and management plan for restoration of California grasslands.

Much recent conservation management in the United Kingdom (and indeed throughout the world) is concerned, implicitly or explicitly, with the distinction between a native and a non-native species. The most generally accepted definition in Britain of an alien or non-native species is one introduced by human action since the last ice age, 10,000 years ago. Alien species are generally denied statutory protection, usually regarded by conservationists with deep suspicion and certainly as second-class citizens, and often has a most serious threat to the natural heritage. At the start of the twentieth century, the overriding category was not whether a species was alien or not, but whether it was ‘vermin’ or not. Vermin were species that for one reason or another were regarded as undesirable, usually because they were considered pests of agriculture or horticulture, or enemies to game preservation. Vermin in Great Britain included virtually everything with a hooked bill, mammals such as grey and common seals, otters and badgers as well as foxes and moles, and small birds with a liking for buds and fruit, like bullfinches and blackbirds, sometimes even blue tits.

This chapter tells the story of how a few biologists came to question whether non-native species were being objectively evaluated with regard to their threat to biodiversity and ecosystems. The chapter examines the criteria that are commonly used to evaluate whether species should be labeled as invasive aliens, and suggests there is merit in assessing both the positive and negative contributions of species. Because invasion biology is a heavily value-laden field in which logic does not always reign, there is resistance to considering the benefits that might accrue from non-native species. Now is the time to think hard about which species are likely to cause clear harm so that management interventions can be aimed where they are most needed, and limited resources are not squandered on relatively harmless ecological invasions.

This chapter discusses the annual grassland systems occupying the coastal ranges, central valley, and Sierra Nevada foothills, describing the common non-native invasive species in California Valley and foothill grasslands, including their growth form, classification, and ecological and economic impacts. It also describes several techniques for invasive plant management in California grasslands.

This chapter identifies the ecological factors that influence the availability of water to California grasslands, including abiotic and biotic influences, and describes the extent to which soil water availability varies temporally, spatially, and as the species traits of the vegetation community change. The influence of climatic conditions, including precipitation, on the productivity and species composition of grasslands are also discussed. Finally, the chapter examines how the shift in community composition due to invasion of non-native species into inland grasslands has influenced soil moisture dynamics in California.

This chapter focuses on studies that incorporate experimental evidence to address the amphibian population decline phenomenon. It discusses the major causes of global amphibian declines, such as climate changes, increasing levels of ultraviolet radiation, contaminants, pathogens, and introduced non-native species. It suggests that amphibian population declines are more likely due to multiple stressors, acting either independently or through complex interactions with each other.

Freshwater ecosystems are particularly susceptible to invasions by invasive non-native species (INNS) across a range of taxa, largely as a consequence of anthropogenic influences on these systems, with a number of ecological and socio-economic impacts. This chapter reviews freshwater invasive non-native species across the globe, focusing on fishes, invertebrates, floating macrophytes, and submerged macrophytes emphasising the knowledge gaps in particular that have resulted in biases inherent in assessments of freshwater invasions. These include an ecological bias because the majority of studies focus on terrestrial invasions; a geographical bias as most studies are focused on temperate northern hemisphere systems; and a taxon bias where fish invasions, populate the literature. This chapter highlights some of the approaches needed to survey, monitor, and manage INNS.

Since the mid-20th century we have been living in a new geological epoch, Anthropocene, characterized by an overwhelming impact of human activity on the Earth’s ecosystems, leading to mass species extinction by habitat destruction, pollution, global climate warming, and homogenization of biota by intra- and intercontinental transfer of species. Crustaceans are among the most diverse and species-rich animal groups inhabiting predominantly aquatic ecosystems, listed as among the most threatened ecosystems. Global threats include ocean and freshwater acidification, eutrophication, pesticide, hormone and antibiotic load, coastline modification, habitat destruction, overharvesting, and the introduction of invasive species. Many crustaceans are threatened by human-induced modifications of habitats, while others are themselves threats—crustaceans are among the most common invasive species. Those non-indigenous species, when established and integrated, become important components of existing communities, strongly influencing other components directly and indirectly, including by species replacement. They are a threat mostly to species with similar ecological niches, most often to other crustaceans. It is hard to be optimistic about the future of crustacean biodiversity. We may rather expect that growing human pressure will variously further accelerate the non-natural dispersal and extinction rate.

Although current understanding of the sources, fate and impacts of many contaminants are now well-known and regulated by national and international bodies and conventions, a number remain problematic. Some are produced in very large quantities (e.g. nutrients, detergents, oil) and others are persistent in the environment (e.g. radioactivity and plastics). All are known threats that have either been ignored, took time to manifest, or have been challenging to manage. For most of these pollutants, regulations exist but changes in the nature (e.g. microplastics) or scale (e.g. increased use of fertilisers, increased livestock culture and sewage production, and changes in energy consumption as the global population grows) may mean existing regulation or management is in some way deficient. For others, (e.g. radioactivity, plastics and threats to biosecurity such as non-native invasive species introductions) the challenges associated with regulation and management are yet to be solved.

The distribution and abundance of ants on islands has attracted considerable attention from ecologists and biogeographers, especially since the classic studies by Wilson on the ants of Melanesia and the Pacific islands (Wilson 1961; Wilson and Taylor 1967a,b; see also updates by Morrison 1996, 1997). The species-area curve for Polynesian ants was an important contribution in the development of island biogeography theory (MacArthur and Wilson 1967). Subsequent studies of other island ant faunas, such as those of the Caribbean (Levins et al. 1973; Wilson 1988; Morrison 1998a,b), Japan (Terayama 1982a,b, 1983, 1992), Korea (Choi and Bang 1993; Choi et al. 1993), and island archipelagos in Europe (Baroni Urbani 1971, 1978; Pisarski et al. 1982; Vepsäläínen and Pisarski 1982; Ranta et al. 1983; Boomsma et al. 1987) and North America (Goldstein 1976; Cole 1983a,b), have confirmed the general features of this relationship, although the underlying causative agents and the relative contribution of stochastic and deterministic processes to ant community composition remain points of controversy. The islands in the Sea of Cortés are particularly interesting from a biogeographic standpoint because they vary considerably in size, topography, and isolation. In addition, both oceanic and landbridge islands occur in the gulf, allowing comparisons between faunas that resulted from colonization (assembly) versus relaxation. Nevertheless, the ant assemblages of the gulf islands have received little study. There are a few scattered island records in taxonomic and faunistic papers (Smith 1943; Cole 1968; MacKay et al. 1985). Bernstein (1979) listed 16 ant species from a total of nine Gulf of California islands, but a number of evident misidentifications occur in her list. To the best of our knowledge, no other publications have appeared on the ant communities of these islands. In this chapter, we document the ant species known from islands in the Sea of Cortés and analyze species composition in a selected subset of the better sampled islands. Most of the data come from recent collections made within the last two decades.

This chapter highlights the scale dependence of biodiversity change over time and its consequences for arguments about the instrumental value of biodiversity. While biodiversity is in decline on a global scale, the temporal trends on regional and local scales include cases of biodiversity increase, no change, and decline. Environmental change, anthropogenic or otherwise, causes both local extirpation and colonization of species, and thus turnover in species composition, but not necessarily declines in biodiversity. In some situations, such as plants at the regional scale, human-mediated colonizations have greatly outnumbered extinctions, thus causing a marked increase in species richness. Since the potential influence of biodiversity on ecosystem function and services is mediated to a large degree by local or neighborhood species interactions, these results challenge the generality of the argument that biodiversity loss is putting at risk the ecosystem service benefits people receive from nature.