The discussion of invasive species issues may be framed by the planning theory of “wicked” problems.  Rittel & Webber's formulation of wicked problems specifies ten characteristics, perhaps best considered in the context of social policy planning, 1- 10. Jeff Conklin Ph.D., a computer scientist expanded, or rather refined the definition, with 11-14, below.
1. There is no definitive formulation of a wicked problem.
2. Wicked problems have no stopping rule.
3. Solutions to wicked problems are not true-or-false, but instead better, worse, or good enough.
4. There is no immediate and no ultimate test of a solution to a wicked problem.
5. Every solution to a wicked problem is a "one-shot operation"; because there is no opportunity to learn by trial-and-error, every attempt counts significantly.
6. Wicked problems do not have an enumerable (or an exhaustively describable) set of potential solutions, nor is there a well-described set of permissible operations that may be incorporated into the plan.
7. Every wicked problem is essentially unique.
8. Every wicked problem can be considered to be a symptom of another problem.
9. The existence of a discrepancy representing a wicked problem can be explained in numerous ways. The choice of explanation determines the nature of the problem's resolution.
10. The planner has no right to be wrong (Planners are liable for the consequences of the actions they generate). Further, the planner or designer (solving the problem) has no inherent right to solve the problem, and no permission to make mistakes.
11. The problem is not understood until after formulation of a solution.
Stakeholders have radically different world views and different frames for understanding the problem
12. Constraints and resources to solve the problem change over time.
13. The problem is never solved.
14. Wicked problems are often "solved" (as well as they can be...) through group efforts.
15. Wicked problems require inventive/creative solutions.
16. Every implemented solution to a wicked problem has consequences, and may cause additional problems.
That stakeholders approach invasive species with radically, sometimes absolutely, different world views is a crucial challenge in the effort to bring parties to the table, and even, once the interest groups arrive, given “the information needed to understand the problem depends upon one's idea for solving it” , the conversation may rapidly degenerates into harden contentious disagreement of a subjective ad hominem nature.
From the internet, I am able to find the following definitions:
1. Invasive plants are non-indigenous species or strains that become established in natural plant communities and wild areas, replacing native vegetation. 
2. Invasive plants are species that show a tendency to spread out of control. Although not synonymous with "exotic plants" ("alien plants"), invasive plants often are plants that have been introduced from other regions. Once introduced, such plants spread like wildfire, partly because the insects and diseases that plague these invasive plants in their native lands are often absent in their new homes.
3. The World Conservation Union (IUCN): “Alien Invasive Species” means an alien species, which becomes established in natural, or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity. Convention on Biodiversity (CBD): “Invasive Alien Species” means an alien species whose introduction and/or spread threaten biological diversity. Global Invasive Species Programme (GISP): “Invasive Alien Species” are non-native organisms that cause, or have the potential to cause, harm to the environment, economies, or human health. The National Invasive Alien Species Implementation Action Plan (NIASIAP 2006 Samoa): “Invasive alien species” are species introduced into an area in which they do not occur naturally, usually as a result of human activities, and which threaten environmental or economic resources, or human health, due to the damage they cause, or are likely to cause.
4. The term invasive species refers to a subset of those species defined as introduced species or non-indigenous species.
5. Invasive plants, often referred to as weeds, are introduced species that can thrive in areas beyond their natural range of dispersal. These plants are characteristically adaptable, aggressive and have a high reproductive capacity. Their vigour combined with a lack of natural enemies often leads to outbreak populations.
6. By definition, Invasive Species are newly arrived plants or animals and unless they make two or more plants or animals totally extinct (an unlikely and statistically remote possibility) they INCREASE BIODIVERSITY. This is so entirely self-evident that no further explanation is required.
7. Executive Order 13112 and the National Invasive Species Council Management Plan (NISC, 2001) define “invasive species1” and "alien species2." The Heinz Center Non-native Species Task Group adopts the definition of “invasive species” from the Executive Order and Plan, and its definition of “non-native species” is functionally equivalent to the Executive Order and Plan definition of “alien species” with one important exception: the definition excludes species that are not self-sustaining; i.e., that cannot survive without human intervention.
8. Definition: Invasive species are certain plants, accidentally or intentionally introduced, that displace(sic) native species and adversely affect wildlife habitat, water quality, recreation and biological diversity by crowding out beneficial native species. The policy will provide consistent guidance for any TBG activities that involve planting, soil or vegetation disturbances.
It is important to note that these are definitions from stakeholders who recognize a problem even as they cannot quite agree on a definition. There are stakeholders who have not yet envisioned the problem, and therefore, have not yet arrived at a definition.
Definitions number 6 and foot note 4 require sometime for me to formulate a reply, so will continue this line of discussion in a later post.
If you have a personal favorite definition, please send it to me, or post them to this discussion.
 Rittel, H., and M. Webber; "Dilemmas in a General Theory of Planning" pp 155-169, Policy Sciences, Vol. 4, Elsevier Scientific Publishing Company, Inc., Amsterdam, 1973. [Reprinted in N. Cross (ed.), Developments in Design Methodology, J. Wiley & Sons, Chichester, 1984, pp. 135-144.]
 Jeff Conklin Ph.D., a computer scientist, while expanding upon IBIS , developed gIBIS ("graphical IBIS") while at the Microelectronics & Computing Consortium (MCC) in Austin, Texas. The gIBIS prototype was subsequently turned into a product called QuestMap by Corporate Memory Systems Inc., a spinoff from MCC. This has subsequently evolved into the Compendium hypermedia concept mapping tool. During QuestMap's product life, Conklin also developed Dialogue Mapping as a facilitation skill for using tools in meetings, designed to help groups further understand, and help solve wicked problems. Dialogue Mapping was subsequently integrated with work in knowledge representation and business process re-engineering (Al Selvin and Maarten Sierhuis, originally at NYNEX Science & Technology) to create Conversational Modelling which Compendium is designed to support. Compendium's development is coordinated at the Open University's Knowledge Media Institute, and its source code is freely available[From Wikipedia]
 From: Foreign Affairs Table
 Some bills are going to hit the United States Senate this year that, on the surface, sound like good ideas…until you start to dig deeper into the proposed legislation.
The biggest problem with these bills is the “Invasive Species” language they contain and the definition of the term “Invasive Species.” Again, on the surface, elimination of “Invasive Species” may sound like an important initiative…until you see that “Invasive Species” is defined as “a species that is
1. non-native (or alien) to the ecosystem under consideration and
2. whose introduction causes or is likely to cause economic or environmental harm or harm to human health.
“Invasive Species” can be plants, animals, and other organisms (e.g. microbes). Human actions are the primary means of invasive species introductions.”
Even this doesn’t sound so bad, until you learn that “non-native” means anything that wasn’t here in 1492 when Columbus came. The lists of plants and animals that fall into that category are long and shocking! Brown trout, rainbow trout, sea bass, large mouth bass, pheasants, and chukkas are targeted.
It also shifts the focus away from the need to control all pests, regardless of origin. In addition, elimination of an “Invasive Species” cannot be done without drastic measures such as massive chemical spraying and the negative effects of fully removing a species from an ecosystem are not being considered. Further information on the serious problems of this definition is included below.
Since these bills are active in the Senate there won’t be much time for the people in the communities who will be negatively impacted by these bills to react. That is why I am contacting you now. I am hoping that we will be able to pull together and mobilize now so that when the time comes for us to contact our senators and demand the removal of all “Invasive Species” language from these bills we will be ready.
Following the segment on the flaws in the definition is some additional reading. You are also welcome to contact me directly if you have further questions. Thank you for your time, and hopefully your support as we stand strong to protect our environment and our rights.
Serious problems with the official “Invasive Species” definition:
Obviously controlling species that are causing serious damage to our environment must be done. And at first glance the Invasive Species movement may seem like the way. However, when examining the definition behind the “Invasive Species” movement the flaws and gaps in logic become readily apparent.
The non-native definition shifts the focus away from the need to control all pests, regardless of origin. It also blacklists beneficial non-native plants and animals. In addition, according to University of Maryland scholar Dr. Mark Sagoff, ecologists have to conduct paleoecological studies and other historical research to determine which species are non-native. They cannot tell by examining the current state of an ecosystem.
“Likely to cause environmental harm” is not measurable, has no scientific definition, and is completely subjective.
There is no process defined for determining the environmental impact of plants, animals, and other organisms. In fact, small groups of bureaucrats are able to add items to the nationwide blacklist for plants and animals.
State by state variations in plant and animal concerns are not taken into consideration.
Other things that aren’t apparent in the definition are:
The groups behind this movement want to take the U.S. environment back to pre-1492 conditions by eliminating plants and animals that were not here at that time. This would mean ignoring over 500 years of scientific progress. "Invasive Species" is now an industry in itself, with over $1 Billion being spent by the Federal government alone, most of it in the form of grants, slick publications, and bureaucracy-building.
Pre-Call To Action Alert: “Invasive Species”
 Invasive Plants Association of Wisconsin
 David Beaulieu, About: Landscaping
 USDA APHIS PPQ
 invasive species: Information from Answers.com
 IWMC.org - "Invasive" Species? Make Up Your Mind - James M Beers
 http://www.heinzctr.org/Programs/Reporting/Working Groups/Nonnative/DEFINITIONS_06.pdf