Designing invasive alien plants’ containment strategies
A structured approach to the development of invasive alien plant containment strategies is useful to promote the efficient use of limited resources. By employing theoretical and semi-quantitative models, conditions under which barrier zones should be established and maintained around core infestations and when eradication of outliers should be attempted were estimated. Five containment sub strategies are proposed:
- Employ barrier zones and eradicate outliers: evidence is required that eradication feasibility is high. This concerns for example annual grasses invading crops, as Lolium rigidum (Poaceae) and Bromus diandrus (Poaceae) in Southern Australia which are characterized by relatively low seed persistence (;3 years) and poor non-human-mediated dispersal.
- Employ barrier zones and control outliers: species in this category are not easily eradicable and their spread occurs through short-distance dispersal or human-mediated dispersal. Agricultural weeds having long-lived seeds and predominantly human-mediated dispersal would belong to this category, as would Orobanche ramosa (Orobanchaceae) which is an annual parasitic plant that produces tiny seeds and develops a highly persistent seed bank.
- Do not employ barrier zones but eradicate outliers: for these species, eradication feasibility is high and long-distance dispersal is both prominent and largely non-human-mediated. Examples can be found among woody growth forms, where species often have short-lived seeds and are bird-dispersed. These species are generally invaders of natural ecosystems. Examples include Miconia calvescens (Melastomataceae) which is highly fecund and which has seeds which are bird-dispersed and can persist for more than 15 years.
- Do not employ barrier zones but control outliers: these species are not easily eradicable and exhibit relatively high level of long distance-dispersal, largely through non-human mediated means. Gymnocoronis spilanthoides (Asteraceae, EPPO Observation list of Invasive Alien Plants) has very long lived seeds but its spread via seed dispersal is less important than that achieved through vegetative fragmentation.
- Difficult to categorize: some species are containable under most circumstances, but significant episodes of long distance-dispersal are triggered by major floods or storms. For example, Parthenium hysterophorus (Asteraceae, EPPO Alert List) is a rapidly-maturing annual plant, capable of producing persistent seeds within 4 weeks. This species would appear not to be easily eradicable, although very small infestations have been eradicated on occasion, and has medium containment feasibility. Its spread is largely dependent on human activities, but its seeds have also been dispersed during flood events.
This study shows that semi-quantitative models can be very useful tools in support of decision-making for the management of alien plants invasions.
Panetta D, Cacho O (2014) Designing weed containment strategies: an approach based on feasibility of eradication and containment. Diversity and Distribution DOI: 10.1111/ddi.12170.