Year

2012

Degree Name

Master of Science

Department

School of Earth and Environmental Sciences

Abstract

Climate change, landowner diversity, human socio-cultural and political attitudes, the biological and ecological characteristics of invasive plants and the nature of the communities they invade are the major drivers of plant invasion. The role of landowners in ranking invasive weeds and in adopting appropriate management strategies to limit invasion problems has received insufficient research attention. This thesis aimed to investigate how the complex interaction between bio-physical and socio-political drivers exacerbates the invasion problem and leads to adoption of management strategies to control and/or eradicate invasive plant species. This study was carried out in the Kiama LGA in the Illawarra Region of New South Wales, about 120 kilometres south of Sydney. The specific aims were to: (i) identify and rank major invasive plants and their relative importance of concern across landowner types, (ii) characterise the focus and efforts of invasive weed management strategies adopted across landowner types and (iii) map the invasion network of drivers for Fireweed (Senecio madagascariensis), Lantana (Lantana camara), and Blackthistle (Cirsium vulgare) in the complex ecological, climatic, socio-political and cultural settings of the case study regions.

The thesis drew on a questionnaire based postal survey (Appendix-A), personal interviews with the local weed officer and a literature review of relevant materials about the bio-physical and socio-ecological drivers of plant invasion. First, frequency of occurrences of all landowners (i.e., 355) was calculated to rank the top three invasive plants; Secondly, Pearson’s Chi-Square tests and Non-parametric Mann-Whitney U tests were applied to test the relative importance of concern about the top three invasive plants (i.e., Fireweed, Lantana and Blackthistle) and overall levels of concern of invasive plant species across landowner types (i.e. newer/longer-term landowners and farmers/lifestylers).Thirdly, multiple regression analysis/independent sample t-tests and a one-way between groups analysis of variance were applied to compare whether there are statistically significant differences across landowner types, in terms of days of invasive weed management and days of invasive weed management per hectare (management intensity). Finally, mapping the invasion network of drivers for Fireweed (Senecio madagascariensis), Lantana (Lantana camara), and Blackthistle (Cirsium vulgare) was undertaken using both postal survey data and literature reviews. All statistical analyses relevant to the thesis aims were performed using SPSS (version 19) software.

Results indicated that a total of 50 invasive plant species were perceived as problematic to the rural landowners (i.e. 355) with Fireweed, Lantana, and Blackthistle ranked as the three most problematic weeds. Ranking and perceptions of these top three plant species across landowner types confirmed that both longer-term landowners and farmers ranked and perceived Fireweed as the ‘first’ ranked problematic weed. But ranking and perception of Lantana and Blackthistle as the ‘second’ and ‘third’ ranked weed across landowner types was ambiguous, with both longer-term landowners/farmers and newer landowners/lifestylers ranking and perceiving ‘other weeds’ as their ‘second’ and ‘third’ ranked problematic weed instead of Lantana and Blackthistle. Comparing overall levels of concern of species of interest between different landowner types showed that Fireweed, Blackberry, Bergalia and Parramatta Grass are of most concern to farmers/longer-term landowners, while Wandering Jew is of most concern to lifestylers. Comparing invasive weed management effort across newer and longer-term landowners has revealed statistically insignificant results. This confirmed that landowners classified on the basis of length of land ownership (length of residence) were not significantly associated with aspects of invasive weed management effort. Conversely, comparing invasive weed management effort among conservationists, lifestyle and rural retreaters, farmers and non-commercial agriculturalists has revealed statistically significant results. This confirmed that landowners classified on the basis of best description of land use (landowner type) were significantly associated with aspects of invasive weed management effort. In particular, farmers undertook significantly more days of invasive weed management in total than conservationists, and lifestyle and rural retreaters. Conversely, conservationists, and lifestyle and rural retreaters undertook significantly more days of invasive weed management per hectare. This suggests different styles, modes and focus of invasive plant management across heterogeneous landowner types. Invasion pathways of Fireweed, Lantana and Blackthistle suggested that their potential invasion and invadability will expand due to changing rural land use and land ownership patterns. In addition, climate change is predicted to increase the invasion and invadability of Fireweed and Lantana, while increasing and/or reducing the invasion and invadability of Blackthistle. Although plant invasiveness, less weed management effort by amenity landowners and poor land/ pasture management by traditional farmers are also reported to increase the invasion and invadability of Fireweed, Lantana and Blackthistle, pathways of control have been found to retard the invasion and invadability for above three plant species to some extent.

Although this research has documented the awareness of 50 invasive plant species, Fireweed, Lantana and Blackthistle were identified and ranked by rural landowners and the local weed officer as the top three invasive plant species and Parramatta Grass (Sporobolus africanus, syn. S. indicus var capensis), Madeira Vine (Anredera cordifolia) and African Olive (Olea europea) as ‘emerging weeds’ by the weed officer. It has been concluded that pathways of plant invasion are multifaceted and current management efforts are not sufficient to limit this invasion coverage. Adoption of an integrated invasive weed management approach by combining all issues, specifically climate change, existing social and political issues related to land use and land ownership by amenity oriented lifestylers and introduction and expansion pathways of identified plant species is recommended.

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