SRM: Landcare: CLEARING ALIEN INVADERS
Source: Fynbos Fynmense: making biodiversity work. (read full publication here), Working for Water website, and the website for the South African National Biodiversity Institute - http://www.plantzafrica.com/.
THIRSTY!
Long-term studies at Jonkershoek in the Western Cape show that pine plantations in mountain catchment areas can reduce stream flow by 130–300 mm per year compared to areas with fynbos vegetation.Why the emphasis on clearing alien invaders?
Invasive alien plants pose one of the most serious threats to biodiversity in the Cape Floral Region. The programme to eradicate aliens is spearheaded by the Working for Water programme, administered by the Department of Water Affairs.
Of the estimated 9000 plants introduced to this country, 198 are currently classified as being invasive. It is estimated that these plants cover about 10% of the country and the problem is growing at an exponential rate. If we do not clear invading alien plants in 10 to 20 years we will lose 30% of our run-off to rivers. In 20 to 40 years 74% will be lost.
- Alien plants usually grow more vigorously, reproduce more rapidly and have fewer natural enemies than indigenous plants. Dense groves of a single species of alien plants threaten biodiversity by crowding out more diverse communities of indigenous plants and animals, including rare and locally unique species.
- Ecosystem goods and services like edible and medicinal species, grazing, tourism opportunities and natural pollination services are all threatened by alien invasions.
- Alien plants threaten agriculture by invading potentially productive grazing land and areas where wild flowers are harvested.
- Experiments have shown that alien trees use more water than fynbos; this reduces moisture in the soil and runoff to rivers especially in mountainous areas and on river banks, affecting plants, animals and people.
- Dense stands of wood alien shrubs and trees are highly flammable and increase the intensity of veld fires, the cost of fire control and the risk of damage to human life and property. Destruction of the vegetation and changes to the soil structure increase the risk of soil erosion after fire.
Conservative estimates suggest that the clearing of invasive alien plants by the Working for Water programme generates increased runoff of about 56 million m3 every year; this equates to the full supply capacity of the Wemmershoek Dam!
Declared Weeds & Alien Invader Plants are divided into three categories:
Category 1 Plants. This is the strictest category. These plants may not occur on any land or inland water surface other than in a biological control reserve. Except for the purposes of establishing a biological control reserve, one may not plant, maintain, multiply or propagate such plants, import or sell or acquire propagating material of such plants except with the written exception of the executive officer.
Category 2 Plants. These are plants with a commercial application and may may only be grown in demarcated areas (or biological control reserves). See the Government Gazette listed below for details relating to demarcated areas. Other provisions of category 1 apply.
Category 3 Plants. The regulations regarding these plants are the same as for category 1, except that plants already in existence at the time of the commencement of these regulations are exempt, unless they occur within 30 metres of a 1:50 year flood line of river, stream etc.
What can you do to help?
- If you own land, keep it clear of invading alien plants.
- Do not buy invasive alien plants from nurseries, and do not support nurseries that sell such plants.
- Join a volunteer clearing or hack group
- Buy firewood, charcoal, crafts, furniture, toys, building material, mulch, etc made from invading alien plants.
- Do not bring foreign plants and animals into our country – and do not send ours to other countries (see research section, paper on vectors).
- Inform authorities about land-owners who are causing the spread of invading alien plants.
- Encourage your local authority, agricultural union, school, community, etc to work with the programme.
Training for mechanical clearing of alien invaders
Herbicide spraying on alien invaders
LINKS AND DOWNLOADS
- Control and management options - visit WfW website
- Discover Life - pick4.pick.uga.edu - A useful guide to declared invaders in South Africa. With photographs.
- List of declared Invader plants: here.
For further information please contact Landcare, Agriculture Western Cape.
