8 Conclusions

We have argued that problem-oriented research may assist problem-solving in three ways by, respectively, analysing casual relationships (systems knowledge), clarifying conflicts of interests and values (target knowledge), or contributing to the development of appropriate means for action (transformation knowledge). We have shown that an interest in all three knowledge forms has evolved in invasion research. In the beginning, research on systems knowledge dominated the field, but increasingly the three knowledge forms have been treated more equally. We interpret this evolution towards a more balanced research focus on systems, target and transformation knowledge as an important learning process that has enhanced the effectiveness of the research field. The increased interdisciplinarity and context-specificity of invasion research are in our view two other aspects that have emerged through learning and are critical for the effectiveness of problem-oriented research (compare Kueffer, 2006; Pohl and Hirsch Hadorn, 2007).

In contrast to these advances, we see in particular three shortcomings of the field that hinder the effectiveness of invasion research. First, the existing theoretical frameworks are currently only partly able to integrate natural and social sciences research on the processes underlying invasions. For instance, research on biotic invasions needs to be reconsidered in the context of global change, or human agency has to be incorporated into theoretical frameworks. In the case of transportation processes, vector science has made first important steps towards an integrative framework, but other invasion phases are not covered by this approach. Thereby it may be fruitful to revisit research approaches pre-dating the formation of an explicit research field in the late 1950s, such as the European tradition of ‘adventive floristics’ that had in the late 19th and early 20th centuries already considered the role of human agency in biotic invasions (cf. Kowarik, 2003). Second, a clarification of the normative thinking about alien plant invasions is needed as discussed in the section on the native/alien debate. Third, research on transformation knowledge has so far not fundamentally challenged the existing conceptual framing and institutional setup of invasive species management. However, because biotic invasions are a novel type of complex, multi-scale socioecological processes, that involve a large number of different actors and stakeholders, institutional innovations are needed.

We postulate that these three shortcomings can only be overcome through formal boundary management processes such as transdisciplinary research or participatory processes, which are to date scarce in invasion research. This is because in all three cases, innovations may substantially challenge the problem understanding both in the scientific and management contexts, and power relations among experts and stakeholders may be fundamentally reshaped (cf. Elzinga, 2008). Such inherently post-normal problem framing processes, where both epistemological and social boundaries are fundamentally challenged, require boundary management processes that integrate not only thinking from different disciplines, but also non-academic perspectives. Boundary management must also explicitly address the reshuffling of power relations among experts and stakeholders through processes that are perceived to be fair and impartial by all participants. Over the past decades, transdisciplinary scholarship has developed appropriate methodologies for such processes (see e.g. www.transdisciplinarity.ch or www.anu.edu.au/iisn).

In summary, the long-term problem-orientation of the field of invasion research has allowed for a number of innovations that have significantly enhanced the effectiveness of the science for management. However, for the development of the field, research and management may have to be substantially reconfigured, and this will need structured and explicit boundary management processes such as transdisciplinary research.