Invasive Plants

First collect the weeds and tie them in bundles to be burned; then gather the wheat into my barn.
Matthew 13: 30

What are invasive plants?

Invasive plants are plants that are intentionally or accidentally introduced by humans into areas outside of their natural habitat. These species can spread rapidly with negative consequences for native species.

Invasive plant species have an impact on the diversity of local species, they affect water availability and damage the quality of soil nutrients. Once an alien plant has invaded a habitat, it changes the conditions of that environment. It does so by changing the light, solar radiation and temperature levels in the invaded patches. The quality and availability of food, shelter, nest sites, basking sites and perches are changed for a number of animals.

They can also inflict big changes on native vegetation, altering the frequency of fires, nutrient cycling, water availability and soil erosion. For example, pine trees in the Western Cape Province of South Africa have spread beyond forestry plantations and invaded native fynbos habitat. In these invaded landscapes, the temperatures available to lizards for functioning optimally are generally cooler and the number of lizard species greatly reduced.

In a few cases, some benefits of alien plants have been reported. For example, they can provide fire wood for local communities or add resources for animal species. But these benefits typically do not surpass the negative effects. Invasive plants have an impact on native species through complex interactions and processes.

Habitats that have invasive plants have a poorer diversity of animal species than native habitats. There are multiple reasons for this poorer animal diversity, like reduced availability of food resources or heat conditions that are essential for animal survival.

A nice example of how alien plants impact native animals comes from a study in Lake St. Lucia, on the eastern part of South Africa. Alien vegetation has shaded Nile crocodile nests. Since being invaded, nests are much cooler than normal sunny nests which female crocodiles prefer. Temperature dictates the sex of embryos in reptiles, so this finding implies that development of eggs under these conditions will result in more females. These nest temperature changes could therefore affect the population’s demographics in the long-term and alter higher levels of organisation, like communities and species. So, invasive plant species might affect the environment in more ways than we can imagine.

Find out about invasive plants in your area by going to ECOSIA (instead of google) and find out how to remove or replace them