Indigenous and exotic vegetation
vegetation WHAT IS INDIGENOUS? WHAT IS EXOTIC? BENEFITS AND DISADVANTAGES
EVER wonder where the trees and plants you see in gardens, parks or on school grounds come from? Were they planted there or did they just start growing by themselves? Let’s focus on two terms that can be used to describe plants: indigenous and exotic. We also look at some of SA’s indigenous plants, including rooibos and a carnivorous plant from the Western Cape.
Port Jackson willow (Acacia saligna) was brought from Australia to SA in 1848 to stabilise sand dunes, but because it’s so fast-growing and adaptable it endangers fynbos. Introducing gall rust fungus (Uromycladium tepperianum) from Australia in 1987 has helped limit its spread.
When a plant grows naturally in an area or ecosystem, we say it’s indigenous. An indigenous plant or tree is one that occurs in a specific area without any human intervention. The plant grows there because the climate and soil suit its species.
Exotic refers to vegetation that was brought to an area from another
One of the most common ways of getting rid of alien plants is by simply chopping them down. country by people. This can be intentional or it can happen by accident.
Unlike indigenous vegetation, which is suited to its climate and grows naturally in an area, exotic plants can do much damage to their new environment. Exotic vegetation can make it difficult for indigenous species to grow. When that happens, we call the exotic species aliens. Alien plant species can become a problem when they stifle the growth of the area’s natural (indigenous) species.
When you want to refer to a plant as indigenous or exotic, ask yourself if that species occurs naturally in the area or if it was brought there from elsewhere.
When plants grow in their natural habitat, it’s beneficial to both humans and the environment. Indigenous species are waterwise and adapt their water requirements according to what’s available in their climate.
Indigenous plants also contribute to the ecosystem, which includes insects, birds and animals. They can be a source of food and/or shelter to various species.
The opposite is true for exotic plants, which can be harmful to an environment. These invasive alien species can destroy the natural vegetation, increase the risk of wildfires, and can lead to water shortages for indigenous plants. Exotic trees such as pine and blue gum use a lot of water, leading to shortages in already water-scarce areas.
Many alien species don’t have natural enemies in the new environment where they’ve been moved to. This can lead to them encroaching on the habitat of indigenous species and eventually even cause native species to die out in an area. For example, by 2018 more than 90% of the fynbos in the Garden Route National Park had been supplanted by exotic pine trees.
Exotic species can also have a detrimental effect on biodiversity (the variety of animal and plant species). In wetlands, for example, every plant and animal has a purpose within that ecosystem. If an alien plant should take hold, it disrupts the natural balance of the wetland, which might eventually even dry up because of this.
SA is just one of many countries that has laws to govern or manage exotic species. The commonest method of combating alien vegetation is simply to remove it. Alien species can also be managed through biological processes (see Did You Know? on the left).
Does exotic vegetation have any benefits? Large plantations of fast-growing exotic trees are often cultivated on purpose. These include trees such as the Australian wattle (Acacia pycnantha), a type of acacia. The plantations provide wood for export or for local manufacturing, such as furniture. In this way, exotic trees contribute to the local economy and prevent the deforestation of indigenous trees. INTERESTING PLANTS S SA has a rich variety of indigenous plants, including the colourful carnival bush (Ochna serrulata), which attracts birds and insect to gardens; the African walnut tree (Schotia brachypetala), which sports deep red flowers, is easy to grow and provides plenty of shade; and plumbago (Plumbago auriculata), a resilient shrub that can be cut into hedges.
An indigenous plant that’s world-famous is rooibos (Aspalathus linearis). It’s a fynbos species found only in the Cederberg area of the
Western Cape. While it’s mostly used for tea, the plant also has medicinal and therapeutic properties and is used in cosmetics.
S Carnivorous plants are plants that have evolved to trap and digest insects and other animals. There are about 600 species found on every continent except Antarctica.
The most well known is probably the Venus flytrap (Dionaea muscipula). It’s indigenous to the east coast of America but is available in SA in nurseries as an indoor ornamental plant. It has leaves that snap shut when tiny hairs on their inner surfaces are triggered by movement.
In South Africa we have our own carnivorous plant, the Cape sundew (Drosera capensis). It’s found in the Boland and catches insects by attracting them with drops of sticky sweet fluid secreted by tiny tentacles found on its leaves.
When an insect gets trapped in the goo, the tentacles and even the leaf slowly lean over to enfold it and start digesting it. The tentacles are so sensitive they can distinguish between their prey and other objects such as drops of water. S