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German wasp | Vespula germanica

German wasp

Vespula germanica

Coral bush | Ardisia crenata

Coral bush

Ardisia crenata

Purple loosestrife | Lythrum salicaria

Purple loosestrife

Lythrum salicaria

Pom pom weed | Campuloclinium macrocephalum

Pom pom weed

Campuloclinium macrocephalum

Canarybird bush | Crotalaria agatiflora

Canarybird bush

Crotalaria agatiflora

Peanut butter cassia | Senna didymobotrya

Peanut butter cassia

Senna didymobotrya

Rubber vine | Cryptostegia grandiflora

Rubber vine

Cryptostegia grandiflora

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Environmental Programmes

In order to tackle our country’s socio-economic challenges, the government adopted the Outcomes based approach to improve government performance and providing focus on service delivery. find out more

Impacts of invasive plant species on river systems in South Africa and their implications

Impacts of invasive plant species on river systems in South Africa and their implications
David Le Maitre
CSIR Natural Resources and the Environment

This paper focuses on the impacts of invasive alien plants on the water flows in South Africa based on riparian invasions. Water-use by riparian trees is higher than in the adjacent dryland areas and has significant impacts on river functioning. Wattles and eucalypts are mainly invaders of riparian zones where they frequently become dominant and completely exclude native species. Riparian invaders also alter river sediment dynamics, nutrient fluxes and assimilatory capacity, with significant impacts on ecosystem services. However, we currently do not have adequate information on the extent and impacts of riparian invasions, nor have priorities been set for riparian invasions. Invasive alien plants have invaded most of our river systems, on average about 30%, particularly many of those where water demands are high and water quality is an issue. Modelling of the impacts of invasions suggests a reduction in river flows of about 3%. For example, the landscape mapping suggests that only about 4-5% of invasions by Acacia mearnsii, Eucalyptus, Populus and Salix species are riparian. A more reasonable split for these taxa would be about 20%, 50%, 80% and 80% respectively. If the riparian invasions are adjusted accordingly, riparian reductions would increase by about 1 000 million m3/yr and the total reductions by nearly 70%. Invasions have many other impacts including altering river ecosystem structure and functioning, aquatic-terrestrial interactions, and ecosystem service delivery. More studies of the extent and impacts of riparian invasions are needed so that appropriate actions can be taken, including defining riparian zones.

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General News Updates

2019 National Symposium on Biological Invasio…

26-02-2019

This is your invitation to South Africa's 2019 National Symposium on Biological Invasions. The convention is hosted by the Centre for Invasion Biology (CIB), University of Stellenbosch, and the Biolo... Read more

2019 Invasive Species Training

22-01-2019

During the past five years (2014-2018), ISSA invasive species trainers have trained 4 000 in the identification of invasive species and laws pertaining to invasive species across South Africa.  ... Read more

Alien Grass Working Group

04-09-2018

Who are we? The South African National Alien Grass Working Group was jointly initiated by the South African Biodiversity Institute (SANBI) and the Centre for Excellence in Invasion Biology (C·I·B) in... Read more

Permits for planting indigenous Cynodon?

01-03-2018

On 16 February, 2018, South Africa's Department of Environmental Affairs issued amendments to the regulations and lists relating to the National List of Invasive Species.  Updates to the draft&n... Read more

Invasive species training 2018 dates released

28-02-2018

Interested in invasive species?  How much do you know about NEMBA invasive species compliance for landowners and organs of state? The South African Green Industries Council (SAGIC) have released... Read more

Communications post for Africa advertised

25-01-2018

The Nature Conservancy has advertised a brand new post:  Communications Manager, Africa Region. Knowledge of invasive species and water would be an asset in this post. See details below:    Job Titl... Read more