With new research revealing a potentially much more damaging effect than was previously understood, the impact of development on wildlife has been highlighted in a report coauthored by a scientist attached to a Nelson Mandela University research unit.
The report by Peter Law and Mark Fuller has been published on the online research platform ScienceTrends, based in Houston, US.
Law is a research associate at the Centre for African Ecology at NMU and the report focuses on wind farms – a growing phenomenon in the Eastern Cape.
While wind farms – bringing with them the possibility of public-private partnerships and the promise of energy free of the carbon emissions that drive climate change – have in general been welcomed, they have also been socially and environmentally controversial, with eco-concerns often linked to SA’s rich biodiversity and vulnerable bird and bat species.
Until now, the impact of a wind farm on wildlife has been measured by tallying the number of carcasses of a particular species and matching the figure against the local population.
But without factoring in the “demographic cost”, this impact might be seriously underestimated, the report says.
It is already a recognised fact that birds and bats are killed directly on wind farms, either from colliding with turbine blades or masts, or from air decompression which causes their organs to rupture.
But there are also individuals that are affected indirectly and they suffer a crucial “reduction in fitness”.
“This component is essential for the identification of a hazard and for alerting scientists/managers to the existence of individuals that are a less visible yet integral part of assessing the overall cost of the hazard,” the report says
The authors based their concept on fieldwork done in California in the US on the Altamont Pass Wind Resource.
Between 55 and 65 golden eagles, primarily sub-adults and “floaters”, that provide replacements when breeders die, are killed at Altamont each year. There had been no noticeable decline yet the loss was substantial.
Law and Fuller did some arithmetic to probe further. Using the average age of the eagles killed (40 months) and an estimate of the number of chicks delivered annually by a breeding pair, “they computed the number of territorial pairs required to be self-sustaining and produce a specified number of offspring that survive to the age of 40 months”.
The answer of 3.93 which emerged meant that the estimated number of territorial pairs in the Diablo Range affected directly or indirectly by the wind farm was 216-255.
This “demographic cost” was then compared with the total number of territorial pairs resident in the area – just 280.
The modelling can guide future studies of Altamont and its impact on golden eagles, the report argues.
The approach can also be used to assess a variety of threats to wildlife, from infrastructure projects and toxic spills to nuclear accidents and alien invasive predators.
“It highlights the need to address our conceptual scheme for evaluating the hazardous prospects of other wind farms and hazards more generally.”
Centre for African Ecology director Prof Graham Kerley said the report highlighted the need to gauge the effect of project applications across entire landscapes and not just on adjacent wildlife populations.
“At the moment in South Africa our legislation is geared around a fragmented site-specific approach and we need to change this to an integrated approach,” Kerley said.