Arctic Biodiversity Assessment - CAFF

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Arctic Biodiversity Assessment

An increasing number of human-introduced species are becoming established in the Arctic and putting indigenous species under pressure. Many more potentially disruptive alien species are found in the sub-Arctic and will probably be able to spread northward in a warming climate. One such species is Nootka lupin Lupinus nootkatensis spreading extensively in Iceland and also found in S Greenland. Photo: Sigurður H. Magnússon.

559 Chapter 16

Invasive Species: Human-Induced Authors Dennis R. Lassuy and Patrick N. Lewis

Contents Summary  �� 560 16.1. Introduction  �� 560 16.2. Status and trends  �� 560 16.3. Conclusions and recommendations  �� 562 References   �� 564

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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.

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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 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).

16.1. 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.

16.2. STATUS AND TRENDS Biological invasions are known from around the globe, but fewer are known from the Arctic compared with lower latitudes. Perhaps the best known Arctic invasion examples are American mink Mustela vison in Iceland and northern Scandinavia (Birnbaum 2007), Nootka lupin Lupinus nootkatensis in Iceland (Magnusson 2010) and Pacific red king crab Paralithodes camtschaticus in the Barents Sea (Oug et al. 2011). In the case of the American mink, its introduction has been cited as a factor in population declines of ground nesting birds and small mammals, as well as the decline of the native European mink Mustela lutreola (Bevanger & Henriksen 1995, DAISIE 2012). The pattern of fewer invasive species at high latitudes may in part reflect that there have been fewer Arctic studies, but it is also consistent with the findings of de Rivera et al. (2005) whose work on marine ecosystems found a pattern of decreasing diversity and abundance of non-native species with increasing latitude. For terrestrial plants, M. Carlson (pers. com.) suggests a range of potential mechanisms that may contribute to this reduced pattern of non-native species invasion at high latitudes: • Increasing proportion of widespread species at higher latitudes (i.e. less regional endemism translates into fewer species that could show up as new); • Some Arctic and sub-Arctic habitats were recently disturbed by glaciations and are colonized by highly ruderal species already;

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• Movement of propagules in the circumpolar region appears to be facilitated by ice, winds and currents (Abbott & Brochmann 2003); and • Densities of people, roads and substrate disturbance decreases with increasing latitude. This does not mean the Arctic is not susceptible to invasion. In fact, changes in climate and patterns of human use are likely to increase that susceptibility. For example, de Rivera et al. (2011) suggest that several marine invasive species, such as European green crab Carcinus maenas introduced to the US West Coast, have the potential to secondarily expand into sub-Arctic and Arctic waters even under moderate climate change scenarios. Similarly, Ruiz & Hewitt (2009) concluded that “environmental changes may greatly increase invasion opportunity at high northern latitudes due to shipping, mineral exploration, shoreline development, and other human responses.” Christiansen & Reist (Chapter 6) suggest “the high potential for negative effects on native species” from introduced fish species (e.g. from aquaculture and translocations) warrants a heightened concern, a finding generally consistent with observations at lower latitudes (Lassuy 1995). To this list of potential Arctic invasion sources we can certainly add tourism, both land- and ship-based, as an increasingly important pathway. Each of these could increase the numbers and dispersal patterns of invasive species or their propagules.

Number of transits throught the Northwest Passage

The introduction of invasive species complicates ecological interactions that are already responding to northward expansion of naturally occurring species (Cheung et al. 2009). Ruiz et al. (2000) found that the rate of marine invasion is increasing; that most reported invasions are by crustaceans and molluscs; and, importantly, that most invasions have resulted from shipping. Other studies (Lewis et al. 2003, 2004) found that the external hull

and ballast tanks of vessels operating in ice-covered waters can support a wide variety of non-native marine organisms. The combined findings of these studies have a great deal of relevance for future marine invasive risks to Arctic waters, especially in light of a recent analysis of current Arctic shipping (Arctic Council 2009) and the expansion of shipping being observed along both the Northeast and Northwest Passages as the Arctic becomes increasingly ice free (Fig. 16.1; ENR 2011, Ware et al. 2013). There are many other potential vectors of aquatic invasive species introduction (marine debris; translocated piers, docks and pilings; aquarium dumping; scientific and industrial instrumentation; and so on) but most of these, except perhaps the instrumentation, are not yet very prevalent in the Arctic. To date, many fewer non-native terrestrial plants have been recorded in the Arctic than in the more highly altered and invaded ecosystems of lower latitudes. However, Nootka lupin has invaded disturbed sites and heathland vegetation in almost all of Iceland and also occurs in SW Greenland, where it has apparently not yet spread into the tundra vegetation (Daniëls et al., Chapter 9). Even in the high Arctic, a number of non-native terrestrial plant species have been recorded. In Svalbard, Elven & Elvebakk (1996) reported that 15% of the flora from a survey was non-native, and Gederaas et al. (2012) describe nine species as actively reproducing. Here, Coulson et al. (2013) also found numerous non-native invertebrates, apparently largely brought in with soil for greenhouses. Similarly, over a dozen non-native plant species are already known from both the Canadian low and high Arctic ecozones and many more occur in the sub-Arctic (Canadian Food Inspection Agency 2008). In Arctic Alaska, 39 taxa of non-native plants (7% of its total Arctic flora) have already been reported (Carlson

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Figure 16.1. Ship transits of the Northwest Passage 1906-2011. From the NWT State of the Environment report (ENR 2011) with data from NORDREG updated to 2012.

562 et al. 2008), and the rates of introduction and establishment in natural systems in Alaska are accelerating (Carlson & Shephard 2007). Among the known nonnatives are several highly invasive grasses and clovers. For example, white sweetclover Melilotus alba, which was extensively used as a forage crop for cattle and a nectar source for introduced honeybees, has now spread up the road system to the sub- and low Arctic in both United States and Canada (Oldham 2007). This nitrogen fixing invader has the potential to alter soil chemistry and has been shown to increase mortality of co-occurring plants, potentially altering successional pathways on floodplains (Spellman & Wurtz 2011). In the Alaskan sub-Arctic, over 75 invasive plant species have been recorded with a dozen of them ranked as ‘highly’ or ‘extremely’ invasive (AKEPIC 2012). In addition to white sweetclover, other extremely invasive plant species include spotted knapweed Centaurea stoebe, reed canarygrass Phalaris arundinaceae and ornamental jewelweed Impatiens glandulifera. Among the highly invasive non-native plant species are orange hawkweed Hieracium aurantiacum, western waterweed Elodea nuttallii and cheatgrass Bromus tectorum, all of which are well documented as being capable of dramatically altering ecosystem function. With climate change enabling invasive species range expansion and resource development intensifying and expanding invasion pathways, the susceptibility of the Arctic to non-native species invasion, particularly from the neighboring sub-Arctic zone, is certainly increasing.

16.3. 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 intro-


duced 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, 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). However, even these valuable data repositories could additionally benefit from improved collaboration on standards for databases, reporting and access. 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 (Ware et al. 2013). 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)


Figure 16.2. Current potential range of non-native aquatic plant hydrilla Hydrilla spp. if it invaded Alaska today and projected potential range with climate warming. (Adapted from Bella 2009).

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564 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.

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565 Weslawski, J.M., Kendall, M.A., Wlodarska-Kowalcsuk, M., Iken, K., Kedra, M. et al. 2011. Climate change effects on Arctic fjord and coastal macrobenthic diversity – observations and predictions. Mar. Biodiv. 41: 71-85. Wilcove, D.S., Rothstein, D., Dubow, J. Phillips, A. & Losos, E. 1998. Quantifying threats to imperiled species in the United States. BioScience 48: 607-615.