268
12.1.1 Invasive Alien Species and Global Environmental
Change
Human-mediated IAS introductions, deliberate or unintentional, tend to be much
faster than natural processes (e.g., wind, animal; Theoharides and Dukes 2007;
Hulme 2009; Pyšek et al. 2009; Seebens et al. 2017). Invasion pathways differ
between taxa; intentional transport (escape and release) is most important for plants
and vertebrates, while unintentional transport is more significant for invertebrates,
algae, and microorganisms (Saul et al. 2017). Roads, tracks, and waterways create
natural and artificial corridors for invasion, exposing ecosystems to invasion, particularly in emerging economies where development is rapid (Mortensen et al.
2009; Masters and Norgrove 2010). Globally, the continued expansion of tourism,
air transport, and trade is dramatically heightening propagule pressure and subsequent invasion (Hulme 2015).
Global environmental changes, particularly changes in climate and weather patterns, nutrient cycles, and land use, generally drive increasing invasions while also
making invasion prevalence, impacts, and feedbacks to the Earth system less predictable (Bradley et al. 2010; Dukes and Mooney 1999). These same change processes can also alter IAS transport and introduction mechanisms, hindering
monitoring and control (Hellmann et al. 2008; Walther et al. 2009) and making it
more challenging to predict future spread. Moreover, these changes stress ecosystems and increase invasion success (Simberloff 2000). Climate and land use changes
drive species range shifts, potentially creating new invasion hotspots (Bellard et al.
2013; Bradley et al. 2010) while decreasing invasion risk and increasing recovery
potential in other regions (Allen and Bradley 2016). Thus, observing the geographic
patterns of the spread of IAS is critical to understand their origins, pathways, and
invasion processes on a changing planet.
12.1.2 Biodiversity Impacts and Global Relevance
Biodiversity provides ecosystems with the capacity to respond to biotic and abiotic
conditions and stress, often used as an indicator of ecosystem resilience. IAS
threaten biodiversity through competition, hybridization, population reduction, and
extinction of native species and modification of habitat. It has been estimated that
42% of all threatened or endangered species are at risk primarily because of IAS
(Pimentel et al. 2005). IAS are able to thrive because they arrive in new ecosystems
without coevolved local competitors, parasites, and pathogens to regulate their
numbers (Keane and Crawley 2002) and are potentially able to exploit resources
and niche spaces that natives cannot (Byers and Noonburg 2003; Levine 2000).
Hybridization with local organisms reduces genetic diversity and further increases
extinction risk (Mooney and Cleland 2001). For example, cheatgrass (Bromus tectorum) introduction to the Great Basin in North America resulted in decreases in
E. A. Bolch et al.
12.1.1 Invasive Alien Species and Global Environmental
Change
Human-mediated IAS introductions, deliberate or unintentional, tend to be much
faster than natural processes (e.g., wind, animal; Theoharides and Dukes 2007;
Hulme 2009; Pyšek et al. 2009; Seebens et al. 2017). Invasion pathways differ
between taxa; intentional transport (escape and release) is most important for plants
and vertebrates, while unintentional transport is more significant for invertebrates,
algae, and microorganisms (Saul et al. 2017). Roads, tracks, and waterways create
natural and artificial corridors for invasion, exposing ecosystems to invasion, particularly in emerging economies where development is rapid (Mortensen et al.
2009; Masters and Norgrove 2010). Globally, the continued expansion of tourism,
air transport, and trade is dramatically heightening propagule pressure and subsequent invasion (Hulme 2015).
Global environmental changes, particularly changes in climate and weather patterns, nutrient cycles, and land use, generally drive increasing invasions while also
making invasion prevalence, impacts, and feedbacks to the Earth system less predictable (Bradley et al. 2010; Dukes and Mooney 1999). These same change processes can also alter IAS transport and introduction mechanisms, hindering
monitoring and control (Hellmann et al. 2008; Walther et al. 2009) and making it
more challenging to predict future spread. Moreover, these changes stress ecosystems and increase invasion success (Simberloff 2000). Climate and land use changes
drive species range shifts, potentially creating new invasion hotspots (Bellard et al.
2013; Bradley et al. 2010) while decreasing invasion risk and increasing recovery
potential in other regions (Allen and Bradley 2016). Thus, observing the geographic
patterns of the spread of IAS is critical to understand their origins, pathways, and
invasion processes on a changing planet.
12.1.2 Biodiversity Impacts and Global Relevance
Biodiversity provides ecosystems with the capacity to respond to biotic and abiotic
conditions and stress, often used as an indicator of ecosystem resilience. IAS
threaten biodiversity through competition, hybridization, population reduction, and
extinction of native species and modification of habitat. It has been estimated that
42% of all threatened or endangered species are at risk primarily because of IAS
(Pimentel et al. 2005). IAS are able to thrive because they arrive in new ecosystems
without coevolved local competitors, parasites, and pathogens to regulate their
numbers (Keane and Crawley 2002) and are potentially able to exploit resources
and niche spaces that natives cannot (Byers and Noonburg 2003; Levine 2000).
Hybridization with local organisms reduces genetic diversity and further increases
extinction risk (Mooney and Cleland 2001). For example, cheatgrass (Bromus tectorum) introduction to the Great Basin in North America resulted in decreases in
E. A. Bolch et al.