When a windfarm was given the go-ahead in the Overberg – in the middle of a landscape surrounded by Critically Endangered Renosterveld, there was reason for great concern.
Windfarms are well-known to cause high numbers of bird deaths (particularly among the larger, long-lived species, and often these are species of conservation concern) in South Africa and the world over, as the spinning turbines become ‘invisible’ to the birds who then collide with them.
And yet, one year later, there’s considerable hope as the Overberg Renosterveld Conservation Trust partners with the windfarm, to find lasting solutions in the area.
The Excelsior Windfarm was completed at the end of 2020 on 2 300 hectares of land outside Swellendam. It’s owned by BioTherm Energy and generates around 33 MW of power. For a country that is once again facing consistent load shedding, additional generating capacity is essential.
Still, the challenge created by the Excelsior Wind farm was related to WHERE it was constructed. The Renosterveld patches that surround the wind farm are home to the Endangered Black Harrier – a flagship species for us given their dependence on Renosterveld and Fynbos habitats.
Black Harriers have been consistently escalated on the Red Data list, as their numbers continue to fall. There are now estimated to be fewer than 1000 mature individuals left in the world. Other windfarms are known to have caused several Black Harrier deaths through collisions.
When we started to assess the Renosterveld around Excelsior for the presence of Black Harriers, we made a remarkable discovery: the area holds what is known to be the highest density of breeding pairs in the Overberg. At one stage, a phenomenal seven breeding pairs were witnessed here.
At this stage, our concern for the fate of Black Harriers here escalated! How could the harriers be protected against potential collisions?
BioTherm Energy, however, has been involved in a big way from the start. And we currently have a number of exciting projects on the go, to protect Black Harriers here.
Here’s what happened:
From the start of construction, BioTherm employed 10 bird monitors, led by the passionate Clarissa Mars – who monitor bird movements from a vantage point close to wind turbines for at least eight hours a day, seven days a week. The moment they witness a Black Harrier (or another threatened bird such as a Cape Vulture or Secretarybird) close to a turbine, they radio this in, and the particular turbine is shut down. This strategy to reduce bird deaths is known as Shut-down on Demand and BioTherm has committed to implement this for the entire 20-year life span of the turbines.
To date, not a single species of conservation concern, or any raptor has been killed by the turbines.
At the same time, we partnered with the Overberg Crane Group and Dr Rob Simmons of the University of Cape Town, to monitor the movements of Black Harriers. Two breeding males were tagged with satellite tags in November 2020. Both pairs bred successfully, with four chicks and one chick hatching from each pair respectively.
We’ve been able to watch their movements closely. At last count, one male had never left the Renosterveld area close to Excelsior. The other made frequent trips to De Hoop Nature Reserve, where the satellite tags last tracked him.
With the help of the Tygerberg Bird Club, we’ll be tagging three more breeding Black Harriers this year, which will give us an even better idea as to their movements around the Excelsior Windfarm and their use of Renosterveld habitats and arable lands for foraging.
BioTherm has also committed to contributing towards the ORCT’s easement programme over the lifespan of the Excelsior Wind Farm, enabling us to offer additional incentives to landowners (in the form of assistance with key management interventions) when undertaking our negotiations for new easements.
What’s more, working with BioTherm, we continue to find ways to protect these birds of prey, assessing new technologies and mitigation measures. Our sincere thanks to BioTherm for their support and contribution in our joint efforts to keep these raptors safe.