Browsing by Author "Sharma, Gyan P."

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    Determining the relationship between invasive alien species density anda country's socio-economic status
    (Academy of Science of South Africa (ASSAf), 2010-04) Sharma, Gyan P.; Esler, Karen J.; Blignaut, James N.
    We explored the relationships between various socio-economic variables and the prevalence and density of invasive alien species (IAS) on a global scale using country-level data sets. We did this by testing the hypothesis that the abundance and distribution of populations of IAS are correlated with various socio-economic indicators, with the direction of causality being that the state of IAS is determined by socio-economic conditions. We found a positive and statistically significant relationship between the prevalence and density of IAS and the human development index (HDI), the satisfaction with life index and the gross domestic product (GDP) among all the countries tested. Additionally, the density of IAS increased significantly with human-population density, total geographic area, GDP and HDI. We also found a positive relationship between the density of IAS and the top 10 road networks of the world. This provides some insight into the development of renewed policies and management strategies for invasive species across both continents and countries. We do caution, however, that the results are likely to be influenced by the sampling factor, whereby affluent countries have more resources to measure and monitor IAS than poorer countries and hence have better records of such, which then indicates a stronger relationship with the level of development. © 2010. The Authors.
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    Insights into invasion and restoration ecology : time to collaborate towards a holistic approach to tackle biological invasions
    (Pensoft, 2012-02-15) Gaertner, Mirijam; Fisher, Judy L.; Sharma, Gyan P.; Esler, Karen J.
    The aim of our study is to provide an integrated framework for the management of alien plant invasions, combining insights and experiences from the fields of invasion and restoration ecology to enable more effective management of invasive species. To determine linkages between the scientific outputs of the two disciplines we used an existing data base on restoration studies between 2000 and 2008 and did a bibliometric analysis. We identified the type of restoration applied, determined by the aim of the study, and conducted a content analysis on 208 selected studies with a link to biological invasions (invasion-restoration studies). We found a total of 1075 articles on ecosystem restoration, with only eight percent of the studies having the main objective to control alien invasions. The content analysis of 208 invasion-restoration studies showed that the majority of the studies focused on causes of degradation other than alien invasions. If invaders were referred to as the main driver of degradation, the prevalent cause for degradation was invaders outcompeting and replacing native species. Mechanical control of alien plant invasions was by far the most common control method used. Measures that went beyond the removal of alien plants were implemented in sixty-five percent of the studies. Although invasion control was not as common as other types of restoration, a closer look at the sub-group of invasion-restoration studies shows a clear link between restoration and invasion ecology. Concerns, as identified in the literature review, are firstly that restoration activities mostly focus on controlling the invader while other underlying causes for degradation are neglected, and secondly that the current approach of dealing with alien invasions lacks a combination of theoretical and practical aspects. We suggest that closer collaboration between invasion and restoration ecologists can help to improve the management of alien plant invasions. We conclude with a framework and a case study from Perth Western Australia integrating the two disciplines, with the aim of informing restoration practice.