Bird electrocution on power lines: Spatial gaps and identification of driving factors at global scales

Universal energy access is one of the targets of the Sustainable Development Goals (SDGs), and thus the deployment of electricity grids is expected to expand globally in the coming decades. However, the installation of power lines is not biodiversity-friendly. In particular, electrocution on power pylons is a major cause of bird mortality worldwide, including for some severely endangered species. Over the last decades, different studies have improved our understanding of the factors influencing the risk of electrocution in birds, but until now spatial gaps in our knowledge of these impacts and the factors driving global patterns of bird electrocution have not been assessed. In this study, we evaluated data from a total of 114 studies that provided information on bird mortality rates on power lines, and we analyzed the factors driving electrocution rates for all bird species, and then for all raptors and large eagles separately. Our results showed a high spatial distribution bias, as more than 80% of the studies were carried out in developed countries, mostly in Europe and North America. By contrast, no systematic studies have been found for Oceania and very few for South America and Africa. Europe showed the highest electrocution rates for birds, South America for raptor species and Africa for eagles. Socio-economic factors best-explained bird and raptor electrocution rates, while climate-related factors were the most influential for eagles. Contrary to our expectations, factors related to pylon design were the least influential on overall electrocution rates. Variables related to study design showed highly variable levels of influence. This could be due to the lack of standardized protocols. Although bird electrocution has been extensively studied, there are large areas where no studies have been carried out or for which data are inaccessible. This could be because in these areas the power distribution network is still sparse, or that most studies are not public or accessible to the international community. Researchers and managers should promote the publication of studies, as awareness is the first step to solving these problems. The factors identified could be applied globally to the design and planning of power grids and the identification of mortality hotspots. This would help mitigate the creation of new mortality hotspots, especially in developing countries where the installation of new power lines has been growing exponentially in recent years.