Environmental Impacts of Transmission Lines on Avifauna
The environmental impacts related to the transmission lines have generated a need for updated and in-depth research on the reflexes of these enterprises, especially on birds. It is estimated that in the world the number of power lines increases at a rate of 5% each year. Forming long networks, transmission lines surpass several habitats, among them some of extreme relevance to birds, such as regular routes between dormitory and feeding areas. The most reported impacts are direct collisions with structures and high voltage cables, as well as some cases of electrocution. The importance of each of these accidents depends on several factors that influence the risk of negative impacts on the bird community, such as the geographical location, the relief, the degree of conservation of this environment, the model of the transmission towers, atmospheric conditions (mist/wind), the taxonomic groups of occurrence and the light conditions (day/night).
In Brazil, there are not many serious problems related to the electrocution of birds in high power transmission lines, due to the fact that the largest size of a Brazilian bird is twice as large as the minimum distance between the conductive phases of high voltage transmission lines. However, such lines present a greater risk of collision, while the greatest risks of electrocution of birds are in transmission lines of medium and low tension, either for passerines or birds of prey. Currently, there is a lack of published studies focusing on bird collisions with transmission lines. However, the published studies add to other information gathered by studies outside Brazil, which can serve to understand the dynamics and relationships of birds that occur in Brazil. Although Brazilian bird species are often different from those observed in other continents, there are many taxons (genera, families, etc.) and phytophysiognomies (wetlands, forests, farming areas, etc.) shared between Brazil and the other countries where studies on birds and transmission lines have been published in greater volume.
Thus, it is reasonable to believe that if some species of heron (Ardeidae), birds of prey (Accipitridae e Falconidae), ducks and geese (Anatidae) are heavily impacted in African enterprises (e.g. JENKINS et al., 2010), Americans (e.g. BROWN et al. 1987) and Europeans (e.g. BEVANGER; BROSETH, 2001), the Brazilian species of these same families are equally affected. In addition to these, there is knowledge of paludicolous birds (e.g. Anseriformes) and pigeons (Columbiformes) among the main victims of a collision.
Mitigatory measures should be applied to reduce such impacts of transmission lines on bird life. Some of these are the planning of the location of these lines, the installation of underground cables, and the installation of signposts, which make the cables more visible and in most cases show a reduction in risk and mortality from collision.
Biologist Zenon Ratzlaff Júnior Dra. Thaiane Weinert da Silva
Specialist in Environmental Licensing Biologist/Ornitologist