Sunday, January 24, 2010

Climate Change & Invasive Species - a Dynamic Relationship

We recognize the Administration’s commitment to dealing proactively with global climate change and we particularly applaud the Department of Interior’s establishment of a Climate Change Response Council to synthesize data and coordinate appropriate management of our nation’s lands and waters. We also acknowledge the United States Department of Agriculture’s (USDA) recent, detailed presentation of the impact of climate change in its publication: “Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States.”[1] Yet, in spite of these notable efforts, the issue of climate change and invasive species biology remains both unreported and underappreciated.

ISSUE
Climate change and biological invasion are dynamic interconnected and interdependent phenomena that affect human health and well being through their impact on ecosystem resources, goods and services. This includes dynamic physical and biological processes such as weather and species movement, climate and species adaptation. Ecosystems as well as climate systems maintain their structures and functions by a multiplicity of dynamic equilibriums that are rigorously controlled by interdependent regulating mechanisms. Ecosystems provide services and resources such as agriculture and food security, water supplies, natural resources, wildlife, recreation, and public health and safety nationwide. Without a greater emphasis on scientific research, the issues involving climate and invasive species issues will remain murky and problematic to policy makers and individual stakeholders alike.[2]

Climate is defined as the long-term weather pattern of an area, including temperature, precipitation, and wind.[3] The speed at which physical properties of climate systems change affects the biological functions of an ecosystem’s member species. A change in climate impacts the domain and range of an ecosystem’s function altering the present expected service dynamics and resource outputs. The change in climate patterns and the speed of these changes directly influence biological systems including the ability of invasive species to become established and thrive when introduced into new ecosystem. In turn, the speed of ecosystem change, both physically and biologically, can be dramatically increased by the introduction of invasive species.[4] The interconnectivity and interdependent relationships of climate, ecosystems and invasive species result in complexities that resist simplified absolute solutions. Because ecosystems are defined in part by climate type and the species that inhabit them, invasive species establishment as well as climate change, alters ecosystem type. Consequently, the expected services and resources of a given ecosystem are altered. At a minimum this means a potential dramatic reshuffling of agricultural services and resources such as food, fuel, feed, fiber, flower and forests along with quickly changing land use decision pressures.

The interrelationship between climatic change, the biology of invasive species, and ecosystem resources and utilization by human systems necessitates that all levels of government integrate invasive species considerations into climate change policies. Of critical consideration is the development of practices that strengthen environmental monitoring, management and control of invasive species as a means to minimize impacts on ecosystem resources in response to changing conditions. The physical processes of climate interact with the biological processes of Earth’s ecosystems and in turn are intertwined with the socio-economics of human activities. It is important to understand that climates can exist without biological systems, but useful biological systems are defined by climate; consequently, ecosystem resources and services to humanity are dependent on and supported by a specific narrow range of climate types. [5]

ACTION
Decisive action is required. This briefing paper, prepared for 2010 National Invasive Species Awareness Week (NISAW), provides:

a) Background information on the linkages between invasive species and climate change, and;
b) Recommendations for action by the Federal government to capitalize on the opportunities to integrate invasive species mitigation in climate change policy and reduce the risks of invasive species to the economy, environment, and human health.


BACKGROUND
Natural resource managers are beginning to plan for adaptation to changing climate. Federal, state, and local agencies, tribes, NGOs, and private landowners all play essential roles in addressing invasive species/ecosystem issues. Collaborative programs that link universities, agricultural producers, the fishing and seafood industry, conservation organizations, recreational interests, trade and transportation interests, government agencies, and policymakers are necessary to effectively address the issues. The USDA reports that “… observation and monitoring systems must be able to support analyses that can aid this management challenge, i.e., adapting to change, documenting the rapidity of ecological changes to assist in adjustment of existing management strate­gies and, most importantly, forecasting when poten­tial thresholds of change might occur and assessing how rapidly changes will occur. Ecological fore­casting is one of the specific goals of international programs such as Global Earth Observation System of Systems (GEOSS), but exactly how such programs will fulfill these goals is still in development.”[6]

Changes in climate systems impact all scales and levels of biological organization from single organism to community level ecosystems. Changes in climate affect both aquatic and terrestrial ecosystems. In a report on the impact of climate change on marine fisheries and aquaculture, Barange and Perry remind us that the “…combination of these proximate impacts results in emergent ecological responses, which include alterations in species distributions, biodiversity, productivity and micro-evolutionary processes (Harley et al., 2006).”[7] The implication of these changes in climate is a movement of species out of their near term expected ecosystems into a migration of warm species northwards and a corresponding loss of species in colder ecosystems. These modeling assumptions about species migration are filled with uncertainty in need of funding for research. Uncertainty is found in current distribution information and data affecting the inferred species’ habitat preferences and distribution shifts; in unavailable accurate estimates of population and dispersal parameters, changes in aquatic or terrestrial chemistry; in synergistic effects between species or anthropogenic factors; and species’ genotypic or phenotypic adaptations.[8] Climate system change dynamics on marine ecosystems, for example, using bioclimate envelopes could “…model changes in species’ distributions and abundance patterns as a result of climate change. The increasing experimentation in culture operations for a wide variety of marine and freshwater vertebrate and invertebrate species should provide opportunities to learn more about their responses to environmental conditions and which conditions lead to optimal (and suboptimal) growth.”[9]

Integral to any policy or practice is the ability to acquire integrated physical, biological and economic data on climate and invasive species relationships over multiple scales of time and space in order to improve forecast models and resource management response to environmental change. Efforts to monitor and provide data sets such as the Invasive Plant Atlas of New England’s (IPANE) and the Center for Invasive Species and Ecosystem Health’s EDDMapS are examples of invaluable non governmental resources in need of ongoing funding sources. Current data provides a mechanism for Early Detection and Rapid Response (EDRR) implementation and additional research. A current assessment of invasive species distribution across the U.S. and North America a function of current and future climatic trends will be necessary to implement ecosystem management policies. Such policies can, potentially range from resource allocation for protection of endangered species to interdiction and eradication of resource altering invasive species. Additional collaboration with organization such as the National Ecological Observatory Network (NEON), which collects and provides information on how land use, climate change and invasive species affect biodiversity, disease ecology, and ecosystem services, provides an example of a platform for holistic ecosystem decision making and management.

The economic basis for invasive species management decisions is provided by the work of USDA Economic Research Service’s (ERS) Program of Research on the Economics of Invasive Species Management (PREISM). The economic information assists decision makers and managers on challenges concerning invasive species questions, policies, and programs addressing invasive species issues related to exclusion, detection, monitoring, eradication, control, and restoration, and their domestic and international components. Bioeconomic principles integrate economic, ecologic and biological data providing policy and management support.[10]

The interaction between the physical (abiotic) changes associated with climate, and the biological processes and interactions of species and food-webs is key to understanding ecosystem function. Leaf canopy and plant diversity within an ecosystem affect macroclimate and subsequently the ability of invasive species to invade ecosystems. Current research modeling attempts to assess at multi-scalar levels the coupled land atmosphere interactions for weather and climate are ongoing but multiyear data sets are rare reflecting the complexity of abiotic and biotic exchanges.[11] The biodynamic interactions of ecosystems for example can register changes in soil moisture as well as seasonal changes in vegetation over various time and spatial scales. Along with these changes, the energy of the sun affects differing surfaces, creating variations in the evolution of temperature and humidity at the surface. The temperature and humidity variations cause dynamic reactions throughout the atmosphere resulting in the winds and clouds. These stochastic processes define weather and climate and consequently the nature and diversity of any ecosystem. The climate of any ecosystem is associated with a specific plant community, (e.g. deserts, rainforest), which in turn, converts light into chemical energy trophic chains and food webs. Respiration by the individual biological organisms and the system itself becomes a part of the climate cycle in a grand interdependent process. The seasonal nature of plant growth and reproduction is connected and dependent upon the size and stochastic nature of climate dynamics.[12]

Ecosystem Impacts
As climate changes therefore, plant communities and their associate animal hosts shift accordingly, with subsequent effects on ecosystem function. If climate increases the opportunities for invasive species to establish, due to the degree or rapidity of the shift, then the ecosystem services, including land-use, human health, economic inputs and quality of life may change according.[13] Historic rates of migration (;10–50 km/100 yr) [14] will be influenced by both habitat fragmentation and the speed of climate change. Potential redistributions of species, therefore, will not happen without human intervention. Climate is among the most important determiners of a species ability to survive and thrive in a particular geographic area and determines in part an invasive species’ viability and impact on expected, necessary ecosystem services and resources. Invasive species are symptomatic of climate change as well as environmental disturbance. The web of strong and weak interactions of climate, human activity and invasive species defines each local ecological system and taken together define Earth’s biosphere. Managing only one of the three processes without consideration of the other two leads to ineffective outcomes.

Climate regulation is influenced by land cover. In some instances, invasive species may effect the emission of NOx, N2O, NH3, and CH4 from altered ecosystems.[15] Invasive species can alter the plant composition of ecosystems and change their structure and function over large areas. As an example: a U.S. Forest Service report finds that “[c]limate change and associated vegetation change interacting with invasive species are also increasingly leading to large wildfires that can further facilitate the establishment of additional invasive plant species.”[16] Further it is conjectured that invasive species “…such as Lepidium latifolium (perennial pepperweed) and Lythrum salicaria (purple loosestrife) change the amount and composition of wetland vegetation in western North America, and may alter regional methane emission, although this remains unstudied.”[17]

Fire which is a physical phenomenon influenced by both the biology of a system and its climate type causes ecosystem disturbances and changes which can allow an intensification of biological invasion. In some sense fire (instantaneous oxidation) and biological invasions (deterministic oxidation by non indigenous species) create the same effect in a native ecosystem. More importantly fire regimes are a determinate process for certain native ecosystems. Changes in climate alter the fire regimes by introducing more or less humidity, more or less rain, or changes in timing and season of precipitation events. Changes in the fire regime of the Sonoran Desert are allowing buffelgrass, Pennisetum ciliare, which tolerates burning better than most long-lived perennials, to persist and spread to the detriment of native species.[18] Along with temperature changes that favor species that germinate and grow better at low temperatures, the hotter fires of buffelgrass combine to create a new ecosystem. The winter storm track of the Sonoran Desert is moving winter rains that “…now generally begin in late November or early December, rather than during the balmy days of late October.”[19]

Climate change may also alter the effectiveness of management strategies for invasive species due to changes in temperature, precipitation, sea level, and carbon dioxide and other atmospheric gases. [20] USDA reports that many plant species “…respond more positively to increasing CO2 than most cash crops, particularly C3 “invasive” weeds.” The same report finds that “…glyphosate, the most widely used herbicide in the United States, loses its efficacy on weeds grown at the increased CO2 levels.”[21] According to Farrar & Williams (1991), although “…[l]ittle information is available for interactions between temperature and CO2. Cold-adapted plants show little response to elevated levels of CO2, with some species showing a decline in biomass accumulation. In general though, increasing temperature will increase sucrose synthesis, transport and utilization for CO2-enriched plants and decrease carbohydrate accumulation within the leaf.”[22] Bunce & Ziska (1995) measured carbon dioxide impact among soy bean cultivars and found that “…increasing atmospheric carbon dioxide concentration may reduce respiration in soybeans, and respiration may be insensitive to climate warming.”[23] Research strongly suggests that while in some plant species carbon dioxide certainly enhances photosynthesis, at the level of leaf canopy, the level of the plant as a whole, the increase carbon dioxide will lead to higher leaf canopy temperatures. And this increase in temperature will lead to an increase in sterility. Increased carbon dioxide will not only cause large leaf and plant structures for our desirable agricultural species, but of course for invasive and weed species that have co-evolved with the crop and humans. The current reduction in farm out-puts (harvests) in Asia could feed over 50 million people. With larger and more vigorous growth of C3 plants including the invasive weeds which compete with the desirable plants, needed farm resource yields will go down and starvation will go up.[24]

The interaction between invasive species, ecosystem dynamics and the exchange of greenhouse gases is also of interest. For example, invasive species can alter the biogeochemical cycles with microbial communities with subsequent effects on greenhouse gas emissions. A study in The ISME Journal states that in “…natural ecosystems, naturally co-evolved belowground multi-tropic interactions may be considerably disrupted when either plants or soil microbes are invading, or when plants or soil microbes are moved to novel environments.”[25] Other studies have found that “(n)on-native plants and animals can alter ecosystem nutrient cycling and soil chemistry through a number of mechanisms. Nitrogen-fixing invaders increase the rate of N input to a system when they replace non- or less-efficiently fixing plants, and when they colonize open areas. (Vitousek & Walker 1989) and (Vitousek et al. 1987) found that the invasion of an N-fixing plant into a young ecosystem in Hawaii increased the rate of ecosystem N accumulation more than fourfold.”[26] A further example is found in an USGS report: “Cheatgrass, (Bromus tectorum), changes the hydrological cycles and biogeochemical cycles, especially carbon and nitrogen, and alters the fire regimes at landscape scales. The species changes the landscape albedo, which affects energy budgets and climate.”[27]

Lewis H. Ziska, a scientist with the USDA-ARS Crop Systems and Global Change Laboratory writes that the “…current distribution of both Japanese honeysuckle and kudzu is limited by low winter temperatures. Global Warming could extend their northern limits by several hundred miles.”[28] However, some invasive species have already taken advantage of warmer temperatures. For example kudzu, an iconic plant invader in the South, has moved steadily northward into the Midwest and was recently spotted in Canada[29]. On the other hand, relatively benign plants that spread northward in warmer temperatures may become invasive pests if their expansion outpaces their natural enemies, according to one study[30]. In marine environments, increasing ocean temperatures may enable invasions of new species such as mussels.[31]

While not the only driver of ecosystem location and function,[32] climate is important to bioeconomic models and management assessment tools[33]. A present, endogenous risk assessment includes niche models that attempt to predict the impact of the physical environment including climate on novel species introductions to ecosystems. However, rapid climate changes can reduce model efficacy and more importantly any policy decision arising from the models. Consequently, the uncertainty presented by invasive species is compounded by the stochastic dynamics of climate change. Fore example, the idea of conserving or preserving specific biological communities at a particular point in time and space is considerably confused or rendered impossible by dramatic changes in climate. The resulting novel ecosystems filled with a new mix of native and non-native species is a field of research still in its infancy. The assisted migration of endangered species may unintentional create new challenges related to biological invasion. Strategic effectiveness requires that we employ sound science to operate from a position of knowledge. Robust monitoring, improved interagency coordination, and expanded research will help us respond quickly, manage efficiently, and take advantage of restoration opportunities that arise.

Invasive species & biological transition states - logical progression
The process of biological invasion, of invasive species movement into and progression within a new ecosystem follows a defined pattern of dynamic states that are non-discrete and continuous over time. The cyclical and iterative processes[34] of biological invasion can be understood as system states of introduction, establishment, naturalization, dispersal, population distribution, and invasion spread.[35] As a major determinant essential for the establishment of a introduced species in a new ecosystem, climate, which is also a cyclical and iterative system, affects each and every stage of the invasion process in ways that are, as yet, difficult to understand and predict.

An introduced organism needs to find climatic and other physical conditions of the environment conducive to its survival. Even if the environment is potentially conducive, the organism needs to find resources necessary for survival, it needs to avoid death, and for many species it needs a mate. Climate affects each of these preconditions of invasion. Both the long term climate patterns and the short term weather events are major factors in determining the viability of the introduced organism. Research by Kolar and Lodge (2002) on non-native fish introduced into the Great Lakes suggested that species with a greater tolerance of abiotic conditions such as temperature may have a greater invasive potential.[36] Increased climate variability would favor those species with phenotypic plasticity and greater genetic variability ability to adapt to unexpected and novel environmental conditions. Work by Franks et al (2007) indicates the importance of seed production and genetic variability in adapting to drought. [37] Understanding of such novel ecosystems that climate change and invasive species will create necessitate theoretical and applied interdisciplinary research.

Physical stressors such as extreme weather events amplify human disturbance patterns providing conditions for invasive species establishment and spread. As the speed of change of climate increases, climate and weather begin to approach each other in scale. This results in physical changes to the ecosystem’s environment (both terrestrially and aquatically) such as water level or change in salinity or acidity. The change in environmental stressors will not only affect invasion biology but will be intrinsic to any study of endangered species. Endangered species and invasive species share the same complex interactions with the physical processes of climate and the socio-economic processes of human disturbance.

Refugium and species diversity functions are reduced and impaired by invasive species. Pimental et al. (2004) note that “[i]nvasive species impact nearly half of the species currently listed as ‘Threatened or Endangered’ under the U.S. Federal Endangered Species Act.”[38] In the Western Ghats where a South American shrub called Siam weed has eliminated most vegetation. The shrub, Chromolaena odorata, introduced in India in the 1840s, produces a chemical, which attracts a fungus, Fusarium semitectum. The fungus causes wilting of local plants and kills seedlings in the vicinity. This species of the sunflower family was and is considered to be one of the most ecologically destructive invasives in the Western Ghats.[39] Habitat loss caused by Arundo donax (giant reed), an escaped garden grass destroys habitat for the endangered bird, the least-billed virio (Raver 1999). Melaleuca quinquenervia has invaded the Everglades crowding out native wildlife (Randall and Marinelli 1996, Fairchild Tropical Garden). [40] Food conversion of solar energy into edible plants and, fodder and fertilizer (e.g. krill, leaves, litter) is impacted by invasive species that reduce yields or destroy crops completely. The economic loss is sufficient for major control efforts to be established by the United States Department of Agriculture.[41] A botanical listing of ecosystem service damaging invasive species totals 896 aquatic and terrestrial species.[42] The loss is not only due to plants, but insects (455 records)[43] and pathogens. An example of an invasive pathogen is “[c]hrysanthemum white rust (Puccinia horiana, "CWR"), a serious fungal disease of chrysanthemums, … can spread quickly in greenhouse and nursery environments, causing severe crop losses.”[44] All of these examples are interconnected and bounded significantly by changes function in climate.

New Pathways for Introductions
Invasive species are both symptomatic of, and contribute to, dysfunctional ecosystems as they reflect an environment under dynamic, constant and unrelenting human and climatic pressures. Human activities provide pathways and are vectors for the introduction and spread of opportunistic, invasive species. [45] Given the exponential increase in international trade and travel, the risk of introducing new species into ecosystems has never been higher. In addition, climate change will alter the routes of planes and ships, especially as new sea routes open up.[46] The U. S. Fish & Wildlife Services wrote in 2997 in Alaska Region Invasive Species News that “[c]limate change can even create new pathways of invasion. An ice-free Northwest Passage in 2007 portends an increase in inter-ocean shipping activity across the Arctic and thus an increase in the movement of species in the ballast water and on the hulls of ships. As climate change enables an increase in arctic development (e.g., oil and gas development and its associated on- and offshore infrastructure), so too does it increase the likelihood of invasion from the movement of bio-fouled drilling rigs and other equipment.”[47] The federal government plays a critical role in preventing the introduction of invasive species through international trade and transport. Ballast water exchange, hull-fouling mitigation, sensible plant and animal import screening, and thorough cargo inspections can help reduce the likelihood of invasive species introductions.

Policy and Legal Responsibilities
Executive Order 13112 requires Federal agencies to address invasive species and establishes the National Invasive Species Council to coordinate planning and response… The International Plant Protection Convention requires analyses of pest risk. Agencies may be able to integrate climate change considerations into their existing risk-assessment protocols and procedures … Environmental laws such as the Endangered Species Act and the National Environmental Protection Act (NEPA) can be used more powerfully to address invasive species.

[1] Rachel Hauser, Steve Archer, Peter Backlund, Jerry Hatfield, Anthony Janetos, Dennis Lettenmaier, Mike G. Ryan, David Schimel, and Margaret Walsh. 2008. The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States. Synthesis and Assessment Product 4.3 (SAP 4.3):. [Online] May 2008. [Cited: December 17, 2009.] http://www.usda.gov/img/content/EffectsofClimateChangeonUSEcosystem.pdf.

[2] Interactions between invasive species and a changing climate have been an area of limited interdisciplinary scientific investigation and funding. author’s note

[3] A. P. M. Baede: [ed.]. Intergovernmental Panel on Climate Change. Working Group I: The Scientific Basis. Appendix I - Glossary. [Online] [Cited: December 17, 2009.] http://www.ipcc.ch/ipccreports/tar/wg1/518.htm.

“Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical climate system.”

[4] Beck, K. G., & Kenneth Zimmerman, J. D. (ISAC 2006). Invasive Species Definition Clarification and Guidance White Paper. Retrieved March 2009, from http://www.invasivespeciesinfo.gov/docs/council/isacdef.pdf

“Executive Order 13112 – defines an invasive species as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.”

[5] Menzel, Annette, et al. . The Atmosphere And The Spatial And Temporal Variability Of. [Online] , . [Cited: December 19, 2009.] www.cms.int/publications/pdf/CMS_CimateChange.pdf .

“… react to variations of its atmospheric environment in a sensitive way and it is astounding as to which precision subjective observations of plants are able to reflect the spatial and temporal variability of atmospheric processes across various temporal and spatial scales.”


[6] Editor: Baede, A.P.M. . (n.d.). Intergovernmental Panel on Climate Change. Working Group I: The Scientific Basis. Retrieved December 17, 2009, from Appendix I - Glossary: http://www.ipcc.ch/ipccreports/tar/wg1/518.htm

[7] Barange, Manuel and Perry, R. Ian. 2009. Physical and ecological impacts of climate change relevant to marine and inland capture fisheries and aquaculture. FAO Document Repository Technical Paper. No. 530. Rome, FAO. pp. 7–106. [Online] 2009. [Cited: December 23, 2009.] ftp://ftp.fao.org/docrep/fao/012/i0994e/i0994e02a.pdf .

“Direct effects of climate change impact the performance of individual organisms at various stages in their life history via changes in physiology, morphology and behaviour. Climate impacts also occur at the population level via changes in transport processes that influence dispersal and recruitment. Community-level effects are mediated by interacting species (e.g. predators, competitors, etc.), and include climate driven changes in both the abundance and the strength of interactions among these species.”

[8] Cheung, William W. L., et al. 2009. Projecting global marine biodiversity impacts under climate. . [Online] 2009. [Cited: December 22, 2009.] http://www.seaaroundus.org/ClimateChange/images/Cheung-climate-biodiversity-FF-2009.pdf .

[9] Barange, Manuel and Perry, R. Ian. 2009. Physical and ecological impacts of climate change relevant to marine and inland capture fisheries and aquaculture. FAO Document Repository Technical Paper. No. 530. Rome, FAO. pp. 7–106. [Online] 2009. [Cited: December 23, 2009.] ftp://ftp.fao.org/docrep/fao/012/i0994e/i0994e02a.pdf .

[10] Keller, Reuben P., et al., [ed.]. 2009. Bioeconomics of Invasive Species: Integrating Ecology, Economic, Policy and Management. New York : Oxford University Press, 2009. p. 298. ISBN 978-0-19--536797-3.

[11] Project Director: D. Niyogi. (2005, October 1). Multiscale Assessments Of The Coupled Land Atmosphere Interactions For Weather And Climate Studies. Retrieved December 18, 2009, from USDA CRIS - Purdue: http://www.reeis.usda.gov/web/crisprojectpages/206061.html

[12] Menzel, Annette, et al. . The Atmosphere And The Spatial And Temporal Variability Of. [Online] , . [Cited: December 19, 2009.] www.cms.int/publications/pdf/CMS_CimateChange.pdf .

“It has turned out that the seasonal cycle of plants is to a large degree linked to the temporal and spatial variability of hemispheric scale atmospheric circulation patterns.”

[13] United States Environmental Protection Agency. (2008). Effects of climate change for aquatic invasive species and implications for management and research. Retrieved from Center for Environmental Assessment, Washington, DC. EPA/600/R-08/014.: http://www.epa.gov/ncea

[14] Iverson, Louis R. and Prasad, Anantha M. 1998. Predicting Abundance Of 80 Tree Species Following Climate. Ecological Monographs, 68(4), pp. 465–485. [Online] 1998. [Cited: December 25, 2009.] http://www.fs.fed.us/ne/delaware/4153/iverson18.pdf .

[15] Dukes, Jeffrey S. and Mooney, Harold A. 2004. Disruption of ecosystem processes in western North America. Revista Chilena de Historia Natural, 77: 411-437 . [Online] 2004. http://dge.stanford.edu/DGE/Dukes/Dukes&Mooney2004.pdf

[16] Tausch, Robin J. 2008. Invasive Plants and Climate Change. U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. . [Online] 2008. http://www.fs.fed.us/ccrc/topics/invasive-plants.shtml.

, “… a warming climate will often lead to an upward elevational migration of plant species. Because of the rapidity of expected changes in climate, individuals of a native plant species may be lost from their lower-elevation limits faster than they will be able to migrate upward and establish into newly created habitat. This will result in stressed communities with fewer plant species distributed over large areas of the landscape. As ecosystems become simplified, their trophic levels are truncated and their trophic interactions reduced.”

[17] Dukes, Jeffrey S. and Mooney, Harold A. 2004. Disruption of ecosystem processes in western North America. Revista Chilena de Historia Natural, 77: 411-437 . [Online] 2004. http://dge.stanford.edu/DGE/Dukes/Dukes&Mooney2004.pdf

[18] Hauser, A. Scott. 2008. Pennisetum ciliare . Fire Effects Information System. [Online] 2008. [Cited: December 29, 2009.] http://www.fs.fed.us/database/feis/ .

[19] Kimball, Sarah and Venable, D. Lawrence. 2009. Warming climate chills Sonoran Desert's spring flowers. University of Arizona . [Online] December 16, 2009. [Cited: December 29, 2009.] http://www.eurekalert.org/pub_releases/2009-12/uoa-wcc121609.php .

[20] Hellmann, J.J., J. E. Byers, B.G. Bierwagen, and J.S. Dukes. 2008. Five potential consequences of climate change for invasive species. James (Jeb) Byers. [Online] 2008. [Cited: December 18, 2009.] http://blackbear.ecology.uga.edu/jebyers/byers

[21] Rachel Hauser, Steve Archer, Peter Backlund, Jerry Hatfield, Anthony Janetos, Dennis Lettenmaier, Mike G. Ryan, David Schimel, and Margaret Walsh. "The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States." Synthesis and Assessment Product 4.3 (SAP 4.3):. May 2008. http://www.usda.gov/img/content/EffectsofClimateChangeonUSEcosystem.pdf (accessed December 17, 2009).

[22] Farrar, J. F. and Williams, M. L. 1991. The effects of increased atmospheric carbon dioxide and temperature on carbon partitioning, source-sink relations and respiration. Plant, Cell & Environment, Volume 14 Issue 8, Pages 819 - 830. [Online] Blackwell Publishing Ltd, May 21, 1991. [Cited: December 29, 2009.]
[23] Bunce, James A and Ziska, Lewis H. 1996. Responses of Respiration to Increases in Carbon Dioxide Concentration and Temperature in Three Soybean Cultivars . Annals of Botany 77: 507-514 . [Online] Oxford Journals, 1996. [Cited: December 29, 2009.] http://aob.oxfordjournals.org/cgi/content/abstract/77/5/507.

[24] From author’s web log - Invasive Notes: http://ipetrus.blogspot.com/2009/10/co2-increase-impact-question-of.html

[25] Putten, Wim H van der and John N Klironomos, David A Wardle. 2007. Microbial ecology of biological invasions. The ISME Journal (2007) 1, 28–37; doi:10.1038/ismej.2007.9. [Online] February 21, 2007. http://www.nature.com/ismej/journal/v1/n1/full/ismej20079a.html.

[26] Dukes, Jeffrey S. and Mooney, Harold A. 2004. Disruption of ecosystem processes in western North America. Revista Chilena de Historia Natural, 77: 411-437 . [Online] 2004.
http://dge.stanford.edu/DGE/Dukes/Dukes&Mooney2004.pdf.

[27] Schnase, John L. 2008. Science/Cheatgrass. USGS, Invasive Species Forecasting System. [Online] May 8, 2008. http://invasivespecies.gsfc.nasa.gov/cheatgrass.html.

[28] Ziska, Lewis H. Climate Change Impacts on Weeds. Climate Change and Agriculture: Promoting Practical and Profitable Responses. [Online] [Cited: December 18, 2009.] http://www.climateandfarming.org/pdfs/FactSheets/III.1Weeds.pdf .

“Changes in temperature and carbon dioxide are likely to have significant direct (CO2 stimulation of weed growth) and indirect effects (climatic variability) on weed biology. In spite of the importance of weed biology in both the environment and in farms, very little is known regarding the impact of these environmental changes on either the reproductive success of agronomic or invasive weeds, or the potential consequences for their management. Yet,
given what is known, it is clear that the agricultural, environmental and health costs of not understanding the impact of CO2 on weed biology may be substantial. It is hoped therefore that the current article may serve to both emphasize the critical nature of this topic, and to serve as an initial guide to those who wish to recognize the ramifications of rising CO2 beyond the polemic of global warming.”

[29] Posted By: Mark Ribble. 2009. Kudzu Plant Creeps its Way into Canada The plant that ate the south is in Leamington. [Online] October 2009. [Cited: December 18, 2009.] http://www.leamingtonpostandshopper.com/ArticleDisplay.aspx?e=1774104 .

[30] University of Florida. Climate Change Opens New Avenue For Spread Of Invasive Plants. ScienceDaily. November 30, 2008. http://www.sciencedaily.com/releases/2008/11/081119161125.htm (accessed December 18, 2009).

[31] United States Environmental Protection Agency. 2008. Predicting Future Introductions of Nonindigenous Species to the Great Lakes (Final Report) . National Center for Environmental Assessment. [Online] 2008. [Cited: December 20, 2009.] http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=190305 .

.
[32] Pearson, Richard G. and Dawson, Terence P. 2003. Predicting the impacts of climate change on the. [Online] 2003. [Cited: December 18, 2009.] http://www.gbif.es/ficheros/Taller_nichos_09/Pearson_Dawson_2003_GEB_Are.pdf .

[33] Keller, Reuben P., et al., [ed.]. 2009. Bioeconomics of Invasive Species: Integrating Ecology, Economic, Policy and Management. New York : Oxford University Press, 2009. p. 298. ISBN 978-0-19--536797-3.

[34] Davis, Mark A. 2009. Invasion Biology. New York : Oxford University Press, 2009. p. 244. ISBN: 978-0-19-921876-9 (Pbk.).

[35]Henderson, Scott, Dawson, Terence P. and Whittaker, Robert J. 2006. Progress in invasive plants research. [Online] 2006. [Cited: December 21, 2009.] http://www.cfr.washington.edu/classes.cfr.303/CurrentResearchInvasive06.pdf.
[36]Davis, Mark A. 2009. Invasion Biology. New York : Oxford University Press, 2009. p. 244. ISBN: 978-0-19-921876-9 (Pbk.).

[37]Franks, Steven J., Sim, Sheina and Weis, Arthur E. 2007. Rapid evolution of flowering time by an annual. PNAS vol. 104, no. 4: 1278–1282. [Online] January 23, 2007. [Cited: December 28, 2009.]
[38] Pimentel, David, Zuniga, Rodolpho and Morrison, Doug. 2004. Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecological Economics, ScienceDirect. [Online] 2004. [Cited: December 21, 2009.] http://ipm.ifas.ufl.edu/pdf/EconomicCosts_invasives.pdf
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[39] Narayanan, Sumana. 2008. Invasive species in Western Ghats affects plants . Journal of Ecology (Vol 96, No 1). [Online] 2008. http://www.indiaenvironmentportal.org.in/node/18562.

[40] Hall, Meredith. 2000. IPlants: Invasive Plants and the Nursery Industry. Center for Environmental Studies. [Online] 2000. http://www.brown.edu/Research/EnvStudies_Theses/full9900/mhall/IPlants/index.html.
[41] Tasker, Alan V. [contact]. 2008. Noxious Weeds Program. USDA APHIS at NAL. [Online] June 11, 2008. http://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/index.shtml.
“The APHIS Federal noxious weed program is designed to prevent the introduction into the United States of nonindigenous invasive plants and to prevent the spread of newly introduced invasive plants within the United States. APHIS noxious weed activities include exclusion, permitting, eradication of incipient infestations, survey, data management, public education, and (in cooperation with other agencies and state agencies) integrated management of introduced weeds, including biological control.”

[42] Sinnott, Quinn [contact]. 2007. National Plant Germplasm System. USDA ARS Germplasm Resources Information Network (GRIN). [Online] April 5, 2007. http://www.ars-grin.gov/npgs/aboutgrin.html.

[43]__________. 2009. Invasive and Exotic Insects. Invasive.org: Center for Invasive Species and Ecosystem Health. [Online] March 5, 2009. http://www.invasive.org/species/insects.cfm.

[44] Massachusetts Introduced Pests Outreach Project . 2008. Pathogen alert: Chrysanthemum White Rust detected in Massachusetts. Massachusetts Dept. of Agricultural Resources and the UMass Extension Agriculture and Landscape Program. [Online] September 28, 2008. http://massnrc.org/pests/linkeddocuments/pestalerts/CWR_Sep2008.html.

[45] Wittenberg, RĂĽdiger and Cock, Matthew J.W. 2001. How to Address One of the Greatest Threats to Biodiversity: A Toolkit of Best Prevention and Management Practices. Global Invasive Species Programme, CAB International, Wallingford, Oxon, UK, xx + xxlots pp. [Online] 2001. http://www.hear.org/Pier/pdf/gisp_toolkit.pdf.

“ Biological invasions by non-native species constitute one of the leading threats to natural ecosystems and biodiversity, and they also impose an enormous cost on agriculture, forestry, fisheries, and other human enterprises, as well as on human health. The ways in which non-native species affect native species and ecosystems are numerous and usually irreversible. The impacts are sometimes massive but often subtle. Natural barriers such as oceans, mountains, rivers, and deserts that allowed the intricate coevolution of species and the development of unique ecosystems have been breached over the past five centuries, and especially during the twentieth century, by rapidly accelerating human trade and travel (Case Study 1.1 “Acceleration of Colonization Rates inHawaii”). Planes, ships, and other forms of modern transport have allowed both deliberate and inadvertent movement of species between different parts of the globe, often resulting in unexpected and sometimes disastrous consequences.”

[46] Pyke, CR, Thomas RT, Porter RD, Hellmann JJ, Dukes JS, Lodge DM, Chavarria G. 2008. Current practices and future opportunities for policy on climate change and invasive species. [Online] 2008. [Cited: December 18, 2009.] https://www.researchgate.net/publication/5279390_Current_practices_and_future_opportunities_for_policy_on_climate_change_and_invasive_species .

[47] United States Fish & Wildlife Service. 2007. Alaska Region Invasive Species News. [Online] September-October 2007. [Cited: December 18, 2009.] http://alaska.fws.gov/fisheries/invasive/pdf/news_1007.pdf .

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