Two ecologists from Stellenbosch University, Prof. Brian van Wilgen and Prof. John Wilson, were the lead authors of South Africa's first national report on the status of invasive species, published by the South African National Biodiversity Institute (SANBI) this week.
The report, The Status of Biological Invasions and their Management in South Africa 2017, is also the first such country-level assessment anywhere in the world that focuses specifically on biological invasions. The report fulfills the legal requirement of the National Environmental Management: Biodiversity Act No 10 of 2004 (NEMBA), which stipulates that SANBI has to submit a report on the status of biological invasions, and the effectiveness of control measures and regulations, to the Minister of Environmental Affairs every three years.
Van Wilgen and Wilson, both from the DST-NRF Centre of Excellence for Invasion Biology at Stellenbosch University, led a team of 37 editors and authors from 14 different organisations to develop a framework and set of indicators for reporting on the status of biological invasions at a national level.
According to Wilson, the values assigned to these indicators have now set a baseline against which trends in future can be measured.
Currently, the scoreboard should set the alarm bells ringing. Using the four indicators as a guideline, the researchers found that the rate of introduction of species is increasing, in line with increases in travel and trade, and currently stands at seven new species per year.
Of the 2 034 alien species known to have established populations outside of cultivation or captivity, 775 have become invasive. Of these, 107 have caused severe negative impacts on the environment, affecting 80 000 km2 (1.4%) of the land area. However, current mechanical and chemical control measures reach less than 3-4% of this invaded area per year. Given that spread rates are between 5 and 10% per year, it is clearly not enough to contain or reduce the problem.
The most worrying indicator is the one measuring the level of success in managing invasions. It stands at only 5.5% despite the fact that at least R12 billion has been spent over the past 20 years.
The report identifies the lack of adequate planning and monitoring of outcomes (rather than inputs) as a key weakness in the management of biological invasions. Another major challenge is implementation and enforcement of existing regulations. In terms of the NE:BA A&S Regulations, management authorities of protected areas and organs of state in all spheres of government are required to prepare “invasive species monitoring, control and eradication plans" and submit those to the Minister of Environmental Affairs and SANBI. There is, however, a very low level of compliance, and plans have been prepared for only 6% of the country, indicating very limited capacity to implement the regulations.
In a similar vein, while effective protocols have been developed to prevent the legal introduction of high-risk alien species, there is little capacity in place to intercept or prevent the import of potentially damaging invasive species. Currently, DEA has a consistent presence at only one of the 72 official ports of entry, and the brunt of border inspections falls to the Department of Agriculture, Forestry and Fisheries (DAFF). An increase in this capacity would potentially deliver major returns on investment by preventing the introduction of further invasive species.
Despite these challenges, there have been successes on a local scale. One such example is the use of biological control: of the 60 invasive plant species targeted for biological control thus far in South Africa, 15 species are now under complete biological control, and another 19 species under a substantial degree of biological control.
Van Wilgen says South Africa is a world leader in this field, and the economic benefits of these interventions have been substantial: “Estimated cost to benefit ratios indicate that, for every R1 invested into biological control, economic losses due to invasive alien plant invasions of between R8 and over R3000 have been avoided."
The report concludes with a list of key messages to policy- and decision makers which can be used as a starting point for the development of a policy-response by the Department of Environmental Affairs.
“Ideally, scientists and policymakers should work together to ensure that sound scientifically-based information relevant to policy-makers is appropriately considered when policy is formulated and implemented, but there are numerous factors that can hinder effective collaboration. This report is an attempt to bridge that gap," Van Wilgen concludes.
On the photos above:
Pine trees invading a fynbos area near Pringle Bay, within the Kogelberg Biosphere Reserve (a World Heritage Site). Unless these invasion can be contained, we stand to loose 30% of Cape Town's water supply as well as hundreds of endemic plant species. Photo: Brian van Wilgen
The purple flowers are Patterson's curse (Echium plantagineum), introduced from southern Europe. It comes to dominate pastures and rangelands, and substantially reduces the production of livestock in these invaded areas. Photo: Brian van Wilgen
Professors John Wilson (left) and Brian van Wilgen were the lead authors for the first national status report on biological invasions in South Africa. Photo: Wiida Basson