Thabo Mohlala
A new tool has been developed to minimise deaths of Verreaux eagles due to collision with turbines blades at the wind farms built across the country to generate alternative energy from winds.
While wind energy is widely viewed as cleaner and sustainable, it also poses threat to flying birds as they collide with wind turbines. The outer tip of turbine blades spin at speeds of up to 290km/hour making the collision more fatal.
Although all soaring birds risk colliding with the turbine blades, it is the Verreaux eagle that “is particularly vulnerable to collisions with wind turbines”. Variously described as “spectacular” charismatic” large bird of prey”, experts say it is highly susceptible to collisions.
According to the University of Cape Town-based Fitzpatrick Institute of African Ornithology (FIAO), which is actively involved in reducing deaths of soaring birds, the “post construction monitoring [of wind farms] has found that diurnal raptors are the most frequently killed bird guild, representing around 35% of all casualties recorded”.
The FIAO said it is not yet known if the eagles simply do not see the moving blades or do not perceive them as threat, adding that in South Africa a considerable number of eagles have already been killed at wind farms.
According to the FIAO the tool will “enable turbine placement to occur in areas that minimise the risk of collision for the Verreaux species”. By 2015 the conservation status of the species in Southern Africa was from ‘Least Concern’ to ‘Vulnerable’ due to their declining numbers.
The institute also noted that collisions could also be significantly reduced if developers build their wind turbines some distance away from areas that are in ‘high-use’ by birds of prey. Typically, this has involved restricting any development, said the FIAO, within a certain distance of active nest sites. This creates circular exclusion buffers around nest sites, however, eagle space is not circular and this method has not proved very satisfactory for either developers or conservationists, the institute added.
Called Verreaux’s Eagle Risk Assessment (VERA) model, the new device was developed jointly by the FIAO, Hawkwatch International while the University of Amsterdam provides a more accurate and reliable information.
It also offers developers more accurate guidance on where to safely build their turbines. The VERA model is described as a computer model built using data collected by attaching GPS tracking devices onto 15 Verreaux’s eagles across South Africa.
Tracking of the eagles started eight years ago, when the first Verreaux’s eagle was fitted with a GPS tracking device. The GPS tracking device was part of Dr Megan Murgatroyd’s PhD at the University of Cape Town and developed at the University of Amsterdam. It can provide a record of where and how high the bird is flying up to every 3 seconds.
It is has been established that by using the VERA model, instead of an exclusion buffer, developers can provide the same level of protection for the eagles but can also “increase the areas of land available for safe wind energy development by around 20%”.
Said Dr Murgatroyd from HawkWatch International: “In short, by using our predictive model to account for habitat use instead of simple buffers around a nest, a greater area of land can be made available for wind energy development without increased mortality risk to raptors.”
The FIAO’s associate professor, Arjun Amar said: “the data that Megan [Dr Murgatroyd] has been able to collect is unparalleled for any eagle in Africa, and has allowed us to build these models,” adding that “our aim is to allow wind energy to be developed in a more sustainable manner, and to reduce the threat these turbines can pose to this important African species.”
The development of the VERA tool has seen a considerably high demand from developers for their proposed wind farms projects across the country. “The best time to run the model is at the very early stages of a project. This way, developers are able to plan their layouts accordingly from the start, instead of having to make major, expensive changes at a later stage,” said Dr Murgatroyd.
She said she is encouraged to see the willingness shown by the developers to voluntarily use the VERA model. “We will now work with Birdlife South Africa to update their guidelines on wind energy and Verreaux’s eagles. This will help to bring the use of VERA into adopted best-practice for Environmental Impact Assessments at all proposed developments which have breeding Verreaux’s eagles”, said Dr Murgatroyd.
