Written by: Dewidine van der Colff and Catherine Browne
Eucalyptus, pines and acacia trees are well established invasive species in South Africa, and like many other invasive alien plant species they were introduced for a good reason. These include for use in the forestry industry, dune stabilisation or they just looked pretty in the garden. Little did we know about their terrible habits of drinking lots of South Africa’s water, competing with indigenous species for space and resources, and even creating dead zones in the soils beneath them.
Interestingly when you see a pine tree, you are likely to see an acacia or a eucalyptus tree nearby. Since they are forestry plantation escapees in most cases, they seem to travel together. They have spread along most of our highways and are present in almost all cities, excluding the dry central parts of South Africa.
As they continue their spread across the landscape, they have become part of our lives. Some people grew up with a eucalyptus tree in their garden, providing shade for many generations, hence giving it cultural value. Others have been depending on acacia (the ones without thorns are invasive aliens) for firewood to provide heat and fuel for cooking. Pines and eucalyptus trees are regularly used as windbreaks or property boundaries. And don’t forget that our local bees love eucalyptus flowers when our native plants have finished flowering. These are just some of the current uses of these invasive aliens, which contribute to the controversies surrounding clearing these species. However, in some areas their benefits outweigh their costs.
The benefit and cost of hosting these species are well understood, as South Africa is the world leader in research on invasive alien plants and has excellent legislation protecting the environment against these species. Invasive alien plant species are taken extremely seriously as they have impacts from the local to the national level – water security being at the forefront. These species even affect property sales. If you are selling your property, you need to declare your weeds, potentially resulting in a reduction in the value of your property. Hence, clearing these species is important to everybody not just for the conservation sector.
This is how can you get involved with controlling invasive alien plants in your own backyard, no matter where you live.
1. Know which species are invasive in your country: each country should have a list of all invasive alien species.
2. Be aware of what you are carrying around (age of globalisation), in some countries like Australia and New Zealand, bringing in any material such as plants without the needed paper work will get you into trouble. Abstain from taking plant material with you when you travel.
3. Get involved in your local neighbourhood with clearing activities such as hacking (an activity where a group of people clear invasive alien plants using a range of methods).
4. Find out what your local conservation agency is doing about invasive alien species, and volunteer your time to assist with these activities.
5. Be proactive, garden with indigenous species as much as possible. Make sure that your garden plants are not listed as an invasive alien plant, as some nurseries aren’t always aware and in some countries there is no legislation guiding the sale of these species.
With the help of the public, we can prevent the establishment of alien plants by preventing introductions and spread of new invaders. In South Africa there is a national invasive species unit based at the South African National Biodiversity Institute (SANBI) and in the Western Cape province, the City of Cape Town has an amazing early detection system that you can use to check whether you have any invasive species hanging around. The Botanical Society of South Africa regularly gets involved with programmes involving clearing of invasive species, so members are already busy cutting down these trees. Similar organisations can be found in other countries.
We cannot completely eradicate the dangerous trio as some of us depend on them for our livelihoods. Even though one extensively consumes our water, another nitrifies our nutrient poor soils and another competes with our native flora for space, we should try to control them and prevent any new introductions in the future.
Support proactive behaviour to create awareness and action in your local area to protect precious biodiversity and indigenous flora. For South Africans you can support our indigenous vegetation by becoming a member of the Botanical Society of South Africa. You can also further show your support by making the Botanical Society your selected beneficiary on your MyPlanet card.