The South African government has spent R7,1 billion (adjusted to 2020 values) between 1998 and 2020 to curb the spread of invasive plants, but we are still struggling to get them under control. What we need is a national strategy that focuses on clearly defined priority sites, improves planning and monitoring, and increases operational efficiency.
This is according to a review conducted by Brian van Wilgen from the Centre for Invasion Biology at Stellenbosch University, Andrew Wannenburgh from the Department of Forestry, Fisheries and the Environment, and John Wilson from the South African National Biodiversity Institute. The findings of their study were published recently in a leading conservation science journal, Biological Conservation.
The researchers reviewed the cost, extent and effectiveness of the management of invasive plants by the government-funded Working for Water programme between 1998 and 2020 – the country's largest intervention for managing invasive plants and for supporting a range of agencies or individuals who are legally responsible for the control of these invasive species.
For their review, they used a broad framework of indicators for assessing inputs (efforts to regulate, money spent, planning coverage and effort expended), outputs (the number of species and the extent of sites treated), and outcomes (the effectiveness of treatments in terms of changes in the extent of invasion and the recovery of biodiversity and ecosystem services) at a national level. Their study is based on (1) spatially explicit data on efforts that targeted selected sites and species for control; (2) surveys of the extent of invasion; and (3) case studies of control effectiveness.
According to the researchers, national surveys suggest that plant invasions have continued to grow in range and abundance over the past 20 years. They add that the effectiveness of control operations at roughly 76 000 sites covering 2,7 million hectares has not been monitored regularly and that only about 14% of the estimated invaded area has been tackled. More than a quarter of the control operations were not in priority areas for biodiversity and/or water conservation.
“This shows that the problem is too large to expect that invasive species can be effectively controlled everywhere in the country," say the researchers.
“Although R310 million (adjusted to 2020 values) has been spent annually since 1998 to clear invasive plants, and progress has been made in places, we still haven't won the battle. Several estimates show that to reduce alien plant invasions to manageable levels everywhere, we will need three to seven times more money.
“It is, therefore, vital that the available funding is used more effectively to achieve control of alien plant invasions in priority areas."
The researchers say that Working for Water, which started out as a bold visionary project with laudable progress in many areas, has been unable to reach its initial goal of creating 20 000 jobs to win the war against invasive alien plants.
“This mismatch between the dream and reality is partly because sufficient funds were never available, but also because clear goals have not been set, and that there are various structural issues which made control less effective than it could have been. Moreover, insufficient monitoring has meant it has been impossible to reliably track the progress that has been made.
“We need high-level plans with long-term (i.e., 20 years and more) goals for priority areas, in terms of which medium-term plans describing the interventions needed to achieve specific targets over 5–10 years can be drawn up. These medium-term plans would then be implemented and monitored according to annual plans of operation. In addition, there is an urgent need to focus available scarce resources on priority areas if meaningful progress is to be made."
The researchers do point out that despite a lack of adequate funding, Working for Water is still viewed as a highly successful programme.
“It has raised awareness of the problem of biological invasions, secured substantial funding to address the issue, cleared invasive plants over extensive areas, and created much-needed employment, training and development opportunities."
They remain optimistic about the programme and say it can play a positive role in ensuring that invasive alien plants are effectively controlled in (or prevented from invading) defined priority areas, provided that several issues are adequately addressed.
“For this to happen, however, the level of funding needs to be increased; the current suite of projects clearly needs to be narrowed down to a manageable set within priority areas; clear, goal-oriented long and medium-term management plans for priority areas must be developed; the use of biological control agents needs to maximise; high-risk species must be eradicated where possible; and the efficiency of managing the invasive species must be improved."
“If our recommendations are followed, all priority sites should develop and implement long and medium-term management plans with clear goals," add the researchers.
- Source: Van Wilgen, B; Wannenburgh A; Wilson, J 2022. A review of two decades of government support for managing alien plant invasions in South Africa. Biological Conservation, Vol 274: doi.org/10.1016/j.biocon.2022.109741
Photo of Black wattle (Acacia mearnsii) invasive alien trees in South Africa courtesy of Wikimedia Commons.