Christian Kull

While a number of plants, animals, and insects in Madagascar have been called ’invasive’, the topic of invasive species has until recently received less attention here than in other island contexts. Some species, often alien to Madagascar and introduced by humans, have expanded their range rapidly and have had both negative and positive effects on landscapes, on native biodiversity, and on livelihoods. Examples include the prickly pear (raketa), the silver wattle (mimosa), and, recently, the Asian common toad (radaka boka). Building on a conceptual approach, my recent paper (link; pdf) in the journal Madagascar Conservation and Development emphasizes the importance of inclusive and deliberative site- and population- specific management of invasive species. The paper analyses three separate concepts commonly used in definitions of invasion: the origin, behaviour, and effects of particular species.

The three components often used in defining invasive species. Different definitions emphasise different components. Source: Kull et al. 2014 (supplementary online material)

It places these concepts in their broader social and ecological context, with particular attention to local perspectives on invasive species. My co-authors and I illustrate these concepts with numerous Malagasy examples from the literature and our own experiences. As I alluded to in a previous post, local people are quite aware of new and/or rapidly spreading plants in their region; they engage more with particular plants than abstract categories like ‘invasive species’; the origins of a plant are not seen as particularly important; and people tend to withhold judgment about newly appeared species and instead search for their uses.   The examples demonstrate that while invasions can have dramatic consequences, there can be multiple, often competing, interests as well as site-specific biophysical, environmental, and cultural considerations that need to be taken into account when designing policy and management interventions. We conclude with a number of lessons learned:

1. “Invasive” is often an imprecise term used for rhetorical effect

2. In discussing invaders, it pays to distinguish between analytical categories like “origins”, “behaviour”, and “impacts”, and between plants, predators, and pathogens.  Being specific about sites and species is important.

3. Many plant and animal populations labeled ‘invasive’ have positive as well as negative impacts.

4.  Social justice and economic development should be considered alongside ecological conservation; deliberative and inclusive management is necessary.

5.  Different management strategies are applicable to different contexts

Thank you to the journal editors for the invitation to pen this piece, and to Jacques Tassin and Stephanie Carrière for their help in drafting the article.