Invasive plant species threatens Idas Valley biodiversity

In an effort to combat the problem of invasive plant species in the Idas Valley Nature Area, a student society at Stellenbosch University recently held a three-hour-long invasive plant hack.

This is according to Luke van Rensburg, a member of Ecomaties, who attended the Invasive Species Hack event on 15 August.

The group mainly focused on removing Black Wattle and Golden Wattle from the area, said Brain Du Preez, a Stellenbosch-based botanist, who attended the event.

Despite the first Invasive Species Hack event at Idas Valley Nature Area being “very productive”, there is still a lot of alien clearing that must take place in the reserve before the alien plants begin to give off seeds, said Brian du Preez, a Stellenbosch-based botanist. PHOTO: Téa Bell

Black Wattle and Golden Wattle are particularly prevalent invasive plant species in the Idas Valley Nature Area, according to Prof Dave Richardson, an ecologist specialising in invasive species. 

These alien plants crowd out native vegetation in the area, use much more water than natural fynbos and burn more intensely, according to Richardson.

Therefore, they should be removed from the Idas Valley Nature Area as soon as possible to reduce future clearing costs and avoid the outbreak of fires, according to Brian du Preez.

Timing it right 

An uncontrolled fire broke out in Idas Valley in Autumn 2021, “so alien plant removals should take place as soon as possible”, claimed Du Preez. 

“Post-fire is the best time to remove aliens, because you get them before they set seed again and, once they do, they grow very quickly,” said Du Preez. This is due to the fact that the soil is much looser after a fire, making it possible to pull out alien plants by hand instead of necessitating expensive equipment, he added.

“It’s much cheaper and less damaging to the environment to take out seedlings instead of chopping down trees,” said Du Preez.  

“Clearing the invasive plants allows the native vegetation to recover. Sometimes just cutting down the alien trees sets the system on a path to recovery,” said Prof Dave Richardson, a Stellenbosch-based ecologist specialising in invasive species. PHOTO: Téa Bell

The trail ahead

Despite the first Invasive Species Hack event being “very productive”, there is still a lot of alien clearing that must take place in the nature reserve before the alien plants begin to give off seeds, said Du Preez.

The Idas Valley Nature Area is co-managed by the Idas Valley community and Stellenbosch Municipality, said Stuart Grobbelaar, spokesperson of the municipality. 

According to Grobbelaar, the municipality is aware of the invasive plant issue in the Idas Valley Nature Area and plans to initiate a clearing event by late October to which they will invite neighbouring landowners.

Eon Hendrickse, the co-founder of Idas Valley Community Trails, said he hopes that more members of the Stellenbosch community will partake in future invasive species clearing events. 

“This is an opportunity for locals and students to connect and […] a platform for sharing knowledge [about our environment],” said Hendrickse. 

Black Wattle and Golden Wattle are alien plants that are prevalent in the Idas Valley Nature Area. Both plants crowd out indigenous vegetation in the area and are a fire hazard. This is according to Brian Du Preez, a Stellenbosch-based botanist. VIDEO: Téa Bell

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