List of Figures

	Figure 1: A conceptualisation of effective problem-oriented research. In situations where facts are highly uncertain and conflicts of interests and values are high (post-normal situations), the effectiveness of science-based societal problem-solving depends simultaneously on the adequateness of i. the causal understanding of the problem, ii. the handling of conflicts of interests and values, and iii. the means of action. Science can contribute to the clarification of these points through the production of systems, target and transformation knowledge, respectively. However, the link between the scientific production of these interdependent knowledge forms and an adequate understanding and handling of the problem is not evident and has to be clarified through deliberation among experts and stakeholders (boundary management). Such boundary management is itself a part of effective problem-oriented research.
	Figure 2: Research on the processes underlying biotic invasions (systems knowledge) increasingly considers human agency as an important explanatory factor. The picture shows a subalpine grassland at the slope of Mauna Kea in Hawaii covered in alien grasses and herbs. The past land use of this area as a cattle ranch, that involved the deliberate sowing of grazing-adapted alien species and the accidental introduction of further alien species as contaminants of the seed, helps to explain the invasion of alien species such as Holcus lanatus, Plantago lanceolata, Senecio madagascariensis or Verbascum thapsus in these areas (Photo by Eva Schumacher).
	Figure 3: Research on target knowledge helps to clarify the valuation of the impacts of invasive species and their management. On tropical oceanic islands, Coconut palms (Cocos nucifera) are an important element of the landscape aesthetics of beaches for tourists (picture above) and a valuable source of food and building material for local people. However, in Seychelles, Coconut palms are considered to be invasive by nature conservationists. Native lowland vegetation, which is a critical habitat for endangered endemic birds, only recovers after the removal of these palms (picture below, Seychelles Magpie Robin Copsychus sechellarum on Aride Island). The valuation of the Coconut palm is further complicated because on many oceanic islands it is not known if the species is native or alien (Photos by Eva Schumacher).
	Figure 4: Research on transformation knowledge enhances the options of actors to take action. The control of an invasive species, for instance, is only effective if the removal is considered in an ecosystem context and a broad alliance of stakeholders support the actions. In Seychelles, control programmes by the Ministry of Environment are accompanied by replanting the targeted areas with native species, whereby the local community is involved. The picture shows school children planting endemic palms after the eradication of the invasive shrub Clidemia hirta (Photo by Stefan Zemp).

	Abstract
1	Introduction
2	A theoretical framework for the analysis of the effectiveness of problem-oriented research
3	The societal problem of biotic invasions and the field of invasion research
	3.1	The societal problem of biotic invasions
	3.2	The field of invasion research
4	The production of systems knowledge – Understanding the processes underlying biotic invasions
	4.1	The classical model
	4.2	Phase transition models
	4.3	Natural experiments
	4.4	Multifactorial analyses of case studies
	4.5	Landscape ecology
	4.6	Vector science
	4.7	Land use science
5	The production of target knowledge – Valuation of the impacts of invasive species
	5.1	Biological impact research
	5.2	The native/alien debate
	5.3	Ecological risk assessment
	5.4	Economic valuation
	5.5	Socioeconomic valuation
6	The production of transformation knowledge – Research that addresses the options for managing biotic invasions
	6.1	Prevention
	6.2	Early detection and eradication
	6.3	The control of invasive species
7	Discussion
	7.1	The evolution of invasion research: The search for an adequate framing of problem-oriented research on biotic invasions
	7.2	Forms of boundary management
8	Conclusions
9	Acknowledgements
	References
	Figures
	Tables