Prosopis is an agroforestry tree that was introduced globally to over 100 countries — including South
Africa. Prosopis went through mass scale distribution and planting, to aid farmers with fodder, shade and fire wood in
the arid parts of South Africa. This tree has since become the second most widespread invasive alien plant group in the country,
having harmful effects on biodiversity and ecosystem services, local economies and human livelihoods.
Stands of Prosopis along the Huntams River, Loeriesfontein. Photo credit: Ross Shackleton
C·I·B PhD student, Ross Shackleton, has recently published a series of papers in which he had a closer
look at the ecological and socio-economic impacts of Prosopis in South Africa. The first study, which was published in the
South African Journal of Botany, looked at the effects of Prosopis invasions on native tree populations. It was
found that invasions of Prosopis had a negative impact on native tree populations by reducing their growth rates and increasing
their mortality. Prosopis invasions also decreased the abundance and number of native trees species along river beds, as well
as reduced the abundance of native grasses and shrubs. This has negative implications for biodiversity, grazing potential and other
services provided by native trees.
In a second study — with more of a social focus — many benefits and costs of Prosopis were raised
by different communities. The study, which was published in AMBIO, raised a number of negative impacts linked with Prosopis,
including the loss of water, grazing potential, land, breakage of infrastructure and reduced economic returns for farmers through high
costs of control and loss of ecosystem services. Farmers were spending on average R 20 000 per annum to alleviate the effects of Prosopis
invasions on their land. This ranged from R 3000 per farm per year to manage sparse invasions, up to R 180 000 per farm per year to
remove areas of dense infestation. The removal of Prosopis amounted to up to R 5000 per ha for dense invasions on land that
was bought for R 1500 per ha.
Recently cleared Prosopis trees along the Molopo River, Kalahari. Photo credit: Ross Shackleton
However, Prosopis was also seen to provide benefits such as fodder, fire wood and shade to communities. It is
also used to produce on organic blood-sugar stabilising product known as “Manna” which leads to job creation. This has led
to contentious issues around the genus and has limited several management approaches in the past. However, the respondents revealed that
they perceive the costs of Prosopis outweigh the benefits and local communities in South Africa are in favour of improved
control of these invasions. “We need to find ways of improving the benefit supply of Prosopis while reducing the costs and
rates of spread within South Africa. Some approaches could be to look further into biological control, or mass scale utilisation of the
tree.” says Ross Shackleton, lead author of the papers.
Read the papers:
- Shackleton R.T., Le Maitre, D.C. and Richardson, D.M. 2015 Prosopis invasions in South Africa: Population structures and impacts on native tree population stability. Journal of Arid Environments, 114: 70-78.
- Shackleton R.T., Le Maitre, D.C. and Richardson, D.M. 2015. Stakeholder perceptions and practices regarding Prosopis (mesquite) invasions and management in South Africa. AMBIO, DOI 10.1007/s13280-014-0597-5.
- Shackleton R.T., Le Maitre, D.C. and Richardson, D.M. 2015. The impact of invasive alien Prosopis species (mesquite) on native plants in different environments in South Africa. South African Journal of Botany, 97: 25-31.
- Shackleton R.T., Le Maitre, D.C., Pasiecznik N.M., and Richardson D.M. 2014. Prosopis: a global assessment of the biogeography, benefits, impacts and management of one of the world’s worst woody invasive plant taxa. AoB Plants, 6: plu027, doi: 101093/apbpla/plu027.
For more information, contact Ross Shackleton at email@example.com