Original Research

Changes in the composition and distribution of alien plants in South Africa: An update from the Southern African Plant Invaders Atlas

Lesley Henderson, John R.U. Wilson
Bothalia | Vol 47, No 2 | a2172 | DOI: https://doi.org/10.4102/abc.v47i2.2172 | © 2017 Lesley Henderson, John R.U. Wilson | This work is licensed under CC Attribution 4.0
Submitted: 06 September 2016 | Published: 31 March 2017

About the author(s)

Lesley Henderson, Agricultural Research Council – Plant Protection Research Institute, South Africa
John R.U. Wilson, South African National Biodiversity Institute (SANBI), Kirstenbosch Research Centre; Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, South Africa


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Abstract

Background: Data on alien species status and occurrence are essential variables for the monitoring and reporting of biological invasions. The Southern African Plant Invaders Atlas (SAPIA) Project has, over the past 23 years, atlassed alien plants growing outside of cultivation.
Objectives: To document changes in the alien plant taxa recorded in SAPIA, assess trends in invasive distributions and explore effects of management and regulations.
Method: The numbers of alien plant taxa recorded were compared between May 2006 and May 2016, and changes in the extent of invasions at a quarter-degree squares (qds) scale were compared between 2000 and 2016. The effectiveness of regulations and interventions was assessed in terms of the relative change in the extent of invasions.
Results: As of May 2016, SAPIA had records for 773 alien plant taxa, an increase of 172 since 2006. Between 2000 and 2016, the number of qds occupied by alien plants increased by ~50%, due both to ongoing sampling and to spread. Successful classical biological control programmes have reduced the rate of spread of some taxa and in a few cases have led to range contractions. However, other interventions had no detectable effect at a qds scale.
Conclusions: South Africa has a growing number of invasive alien plant species across an increasing area. More taxa should be listed under national regulations, but ultimately more needs to be done to ensure that management is strategic and effective. SAPIA is a valuable tool for monitoring alien plant status and should be developed further so that invasions can be accurately tracked over time.

Keywords

invasives monitoring and reporting; essential biodiversity variables; effectiveness of national regulations and interventions

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Crossref Citations

1. Even well-studied groups of alien species might be poorly inventoried: Australian Acacia species in South Africa as a case study
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