Life is a Garden | South Africa |

2. The trouble they cause

Invasive alien plants (IAPs) manage to spread so fast by growing very quickly, producing lots of seeds or having tough invasive root systems.

What damage do they cause?

• They invade land and have covered nearly 8% of South Africa and if we do nothing about the spread of IAPs, the land they occupy could double in the next 15 years.
• They waste water: We lose more than 7% of all water run off to 198 invasive alien plants.
• They threaten biodiversity: Invasive alien plants displace the more delicate and slow growing indigenous plants especially in the Cape Floral Kingdom, one of the world's biodiversity hotspots with some 8 600 species of which 70% occur nowhere else on the planet.

And this is not the only ecosystem under threat; aliens are found along rivers in Mpumalanga, in Northern Province, in kloofs in KwaZulu-Natal, and even in the arid areas of the Northern Cape. These are all areas tourists commonly visit. Biodiversity is one of South Africa's key tourist attractions and earns billions of rands in foreign exchange each year. IAPs could threaten this industry.

IAPs such as the pompom weed are invading grasslands - taking up productive land that could be better used for crops and livestock grazing. In South Africa, IAPs can smother and kill trees, hamper forestry operations, crowd out sweet grazing grass and fatally poison cattle which graze on them in times of drought.

• They cause run away fires and erosion
  Many of invasive trees are ‘born to burn' using fire to germinate seeds in huge numbers afterwards. After fires, and before plants have re-established themselves on burnt ground, invasive aliens leave large patches of bare ground which are vulnerable to erosion. This silts up dams and estuaries and results in poor water quality.
• Many are toxic to humans and livestock
  Tickberry (Lantana camara) is just one of many invaders that is toxic to livestock, resulting in large financial losses to farmers. Common plants such as oleanders, syringas, privets and morning glories are toxic to humans and often eaten by children.
• They take over dams, lakes and rivers
  Water hyacinth has taken over the Benoni Lakes system, water sports at Roodeplaat Dam, north east of Pretoria have come to a grinding halt, and continually clearing the Mzunduzi of water hyacinth near Pietermaritzburg costs millions in taxpayers money each year. Hydrilla, a submerged aquatic invader has taken over 800 hectares of the Pongolapoort Dam, northern KZN.
• They are difficult and expensive to eradicate
  Many are able to evolve constantly - and expensive to remove.

Did you know?

South Africa has spent R400 million a year for the past 15 years attempting to control invasive alien plants and is needing R600 million a year to continue the fight for the next 20 years.