INVASIVE SPECIES: HUMAN INDUCED (Chapter 16)

 Authors: Dennis R. Lassuy and Patrick N. Lewis

SUMMARY

As human society has become more mobile, the transfer of species beyond their native ranges has similarly increased. Human-induced biological invasions now occur around the world and are a leading cause in the loss of biodiversity. While only few invasions are currently known from the Arctic compared with lower latitudes, changes in climate and patterns of human use are likely to increase the susceptibility of Arctic ecosystems to invasion. Much of that increased risk of invasion may come from increased shipping, energy development, mineral exploration and associated shore-based developments such as ports, roads and pipelines.

Because future change will be best understood when measured against a credible baseline, much more work is needed to define the current status of native and invasive species populations in the Arctic. The development of cost-effective early detection monitoring networks will be a challenge, but can be informed by Traditional Ecological Knowledge and may benefit from engaging a network of citizen scientists. There also needs to be increased and targeted prevention efforts to limit the influx of non-native species (e.g. ballast water treatment and the effective cleaning and treatment of ship hulls and drilling rigs brought in from other marine ecosystems).

Mink have spread and become more and more common. I believe they come here both from south [of Finland] and from Norway. Minks are real pests; they eat fish from creeks and ptarmigans and whatever they can catch. Late Saami reindeer herder Ilmari Vuolab, Finland; Helander et al. 2004.

INTRODUCTION

As humans and their goods and services have become increasingly mobile, the intended and unintended transfers of species have also increased. In many cases, the intended benefits of species movement (food, fiber, recreation) have been realized. In other cases, both unintentional and intentional introductions have had harmful results (OTA 1993). The term ‘invasive species’ is used here to refer to species that are not native to a given ecosystem (i.e. when a species is present due to an intentional or unintentional escape, release, dissemination or placement into that ecosystem as a result of human activity) and which may cause economic or environmental harm (including harm to subsistence species and activities) or harm to human health. This definition includes species that disperse secondarily from a site of introduction. It should be noted that even non-native species considered to pose no invasive threat at the time of introduction may exhibit explosive population growth long after their initial establishment in a new environment (Sakai et al. 2001), leading to invasive impacts despite initially being considered benign.

Biological invasion is widely recognized as second only to habitat alteration as a factor in the endangerment and extinction of native species and may be the less reversible of the two (Lassuy 1995, Wilcove et al. 1998). Indeed, many now consider invasive species and climate change to be among the most important ecological challenges facing global ecosystems today (Vitousek et al. 1997, Clavero & Garcia-Berthou 2005, Mainka & Howard 2010, IUCN 2012). The combined effects of invasive species and climate change on biodiversity and ecosystem function can be far reaching; for example, altering community composition, community structure, trophic pathways, trophic interactions, native species distribution, habitat structure and even the evolutionary trajectory and fitness of native species (Mooney & Cleland 2001, Hellman et al. 2008, Rahel & Olden 2008). The impacts of invasive species are also not limited to ecological harm. A subset of just 16 of Canada’s over 1400 identified invasive species has had an estimated annual economic impact of $13-34 billion CAD (Colautti et al. 2006). In the United States, economic impacts of invasive species have been estimated to be in excess of $138 billion USD per year (Pimentel et al. 2000).

Impacts of invasive species on cultural systems are harder to define, but two things are clear: (1) as native biodiversity is lost, so too are the potential human uses of that biodiversity, and (2) a warming climate will increase the likelihood of immigration into the Arctic of warm adapted species (e.g. Weslawski et al. 2011), including those mediated by human activities. The combination of these two factors, plus the use by many Arctic residents of native flora and fauna for subsistence, suggest that biological invasions are a critical and complex issue requiring further study and action. For example, invasive species may force traditional knowledge to adapt and new harvesting patterns to be developed.

CONCLUSIONS AND RECOMMENDATIONS

As climate change alters Arctic ecosystems and enables greater human activity, biological invasion in the Arctic is likely to increase. Arctic terrestrial ecosystems may be predisposed to invasion because many invasive plants are adapted to open disturbed areas (Hierro et al. 2006) and Arctic habitats are characterized by extensive freezethaw cycles and other disturbances. If fire frequency and intensity increase with climate change (Hu et al. 2010), this may further enhance invasion susceptibility. Areas of human disturbance and those located along pathways of human activity (e.g. shipping and road corridors) are the most likely sites of invasion for Arctic habitats. For example, Conn et al. (2008) noted the susceptibility of gravel-rich river corridors to white sweetclover dispersal from bridge crossings.

The ability for a warming climate to directly enhance invasion through altered recruitment timing and growth dynamics has been demonstrated for marine tunicates (Stachowicz et al. 2002). The spread of invasive marine tunicates to the Arctic could interfere with access to benthic food sources for already at risk marine mammals like benthic-feeding whales and pinnipeds. There are similar concerns regarding the effects from the introduced red king crab on benthic communities in northern Norway and the Kola Peninsula (Oug et al. 2011). Further introductions may contribute to accelerated and synergistic impacts (Simberloff & von Holle 1999). Range map scenarios developed for 16 extremely or highly invasive plants either occurring in or at risk of invading Alaska (Bella 2009) also paint a sobering outlook for the future. Fig. 16.2 depicts the potential expansion of one well-known invasive aquatic plant, the waterweed Hydrilla verticillata, northward into the aquatic ecosystems of Arctic Alaska and far eastern Russia.

Because future change will be best understood when measured against a credible baseline, much more baseline survey work similar to that of Ruiz et al. (2006) is needed. Due to the distribution of resources in the Arctic, the development of cost-effective early detection monitoring networks will be a challenge. However, Arctic residents possessing traditional knowledge may greatly assist information gathering and monitoring design by offering observations and evaluations of changes. Engaging a network of citizen scientists, for example through school systems and other public involvement mechanisms, may also offer low-cost and sustainable enhancements to conventional monitoring approaches. The increasingly widespread use and adaptability of tools like smart phones and software applications may also help. The key to an effective citizen as well as professional science network will be strong integration and information flow to and from central repositories, for example the European Network on Invasive Alien Species (NOBANIS 2012) and the Alaska Exotic Plant Information Clearinghouse (AKEPIC 2012). The existence of a credible baseline, combined with cost-effective early detection monitoring and information sharing networks (particularly at invasion-susceptible locations like roads, airports and harbors), will also enhance rapid response capabilities for more environmentally and economically efficient eradication early in the invasion process.

In addition to valid baselines and improved monitoring, there will need to be increased and targeted prevention efforts to limit the influx of non-native species (e.g. effective cleaning and treatment of ship hulls and drilling rigs brought in from other marine ecosystems, and ballast water treatment consistent with the recommendation of the Arctic Marine Shipping Assessment; Arctic Council 2009, 2011). Such measures should be complemented with targeted management plans for activities known to present a high risk of introduction. For example, petroleum drilling rigs have been identified as a significant risk for modern marine introductions, and the increase of petroleum extraction in the Arctic should be accompanied by stringent cleaning and monitoring requirements (NIMPIS 2009). For all invasive species, terrestrial and aquatic, there should be more consistent use of basic prevention tools such as Hazard Analysis & Critical Control Points (HACCP) planning (ASTM 2009) and more attention to pathway risk assessment. Snyder & Anions (2008) provide an excellent example of the use of a pathway-based approach for invasive plants and insects in Northwest Territories, Canada. Chown et al. (2011) provide another excellent example of a pathway-based risk assessment in Antarctica, with some interesting comparisons of tourist versus scientist visitors as vectors of plant propagules.

Two additional future Arctic risks that may accompany climate change are: (1) invasive species, much like climate change, can decrease stability and increase uncertainty in ecosystem function and the evolutionary trajectories of species, and (2) as more temperate ecosystems feel the effects of these climate-induced uncertainties, there may be a push to resort to using Arctic ecosystems as refugia at the receiving end of well-intended but risky efforts to ‘assist’ species in the colonization of new habitats (Ricciardi & Simberloff 2009). Since species’ ability to successfully invade will vary with their physiological capacities and dispersal ability (both natural and susceptibility to human transport), much work is also needed on basic biology and life history traits of potential Arctic invaders in order to effectively assess Arctic vulnerabilities and risks. Finally, we recognize there are many other invasive species such as insects and pathogens that are of potential concern for Arctic ecosystems and people, but these are beyond our expertise and are, at least in part, covered in other sections of this report.