In the era of climate change, the need for renewable sources of energy is soaring high and wind energy is one such alternative to look at. Wind power currently contributes nearly 5% of the total electricity consumption worldwide and is expected to supply one third by 2050. Despite being regarded as clean energy, it still has a significant impact on wildlife, particularly on birds. The root cause of direct bird mortality is due to collision with wind turbines. The density and activity of birds are far less in wind farms, thus altering the surrounding food chain. Construction of roads, buildings, and human activity in wind farms follow habitat modification and disturbances to other animals as well.
Several mitigation measures to make wind farms wildlife-friendly have been taken over time. These include selective shutdown alongside migratory flyways, Radar-based maps and migration forecasts, surveillance by humans and machines powered by AI to detect birds, acoustic deterrents, illuminating turbines with UV light, offshore wind farms, and tilling the soil around the base of turbines to reduce the amount of vegetation and hence the abundance of potential prey species of birds, chiefly insects. These measures, despite being effective come at a cost; they require constant maintenance and habitat management, and loss of revenue due to shutdown.
However, a new study by researchers at the Norwegian Institute for Nature Research, Norway tested the efficacy of contrast painting on one rotor blade, a practical and cost-effective approach to lower bird collisions. The study, published in the journal Ecology and Evolution found a significant reduction of over 70% in the fatality rate of birds at the painted turbines. It is the first dedicated in situ experiment to examine the effectiveness of passive markings to reduce avian collisions at wind turbines.
The study was conducted at the Smøla wind-power plant. Smøla is an archipelago consisting of about 5500 small islands and one large island where the Smøla wind-power plant is situated. These islands are rich in birdlife and it has been designated as an Important Bird Area (IBA) by Birdlife International. There are 68 operational wind turbines at this power plant, each 70 m high with 40 m long rotor blades. The plant was started in 2002 and covers an area of 17.83 km2. The researchers followed a BACI approach (B: before, A: after, C: control, and I: impact) to test the effects of rotor blade painting on bird fatality rates. They compared annual fatality rates at the painted turbines with control (non painted) turbines before and after painting. The study used bird fatality data of about 11 years starting from 2006 until 2016. A long-term baseline data of seven and a half years before and three and a half years after the painting was analysed.
The team of researchers led by Roel May found an average 71.9% drop in the annual fatality rate after applying black paint on one rotor blade of the turbine as compared to the control turbines. The most common bird species affected by collisions were willow ptarmigan (Lagopus lagopus), white-tailed eagle (Haliaeetus albicilla), common snipe (Gallinago gallinago), hooded crow (Corvus cornix), and meadow pipit (Anthus pratensis). The study shows that the contrast painting approach particularly reduced raptor fatalities. No white-tailed eagle carcasses were reported after contrast painting. Raptors are known to be highly susceptible to collisions with wind turbines due to their soaring flight, display, and foraging at rotor-swept height. Other species such as meadow pipit and common snipe having aerial displays are also prone to collisions. However, painting one of the rotor blades with a contrasting paint helps reduce motion blur and makes it more visible to the birds, thus making them more vigilant and evade collisions.
The researchers explain that the visual acuity varies from species to species in birds and in the case of diurnal birds of prey such as white-tailed eagle, it decreases greatly for motionless objects under dim light. Hence the success of contrast painting under dim light remains ambiguous and the researchers suggest integrating other clear temporal cues using reflective paint, myriad reflectors, and flickering lights to improve blade conspicuity. The study emphasises the need for testing the effectiveness of other colour systems such as the use of red and green paint and optical or holographic coatings on rotor blades. The researchers recommend replicating such studies with a greater number of painted turbines and to implement and monitor the measure at different sites to establish the extent of efficacy of this approach.
References:
- May, R., Nygård, T., Falkdalen, U., Åström, J., Hamre, Ø., & Stokke, B. G. Paint it black: Efficacy of increased wind turbine rotor blade visibility to reduce avian fatalities. Ecology and Evolution.
- Thaker, M., Zambre, A., & Bhosale, H. (2018). Wind farms have cascading impacts on ecosystems across trophic levels. Nature ecology & evolution, 2(12), 1854-1858.
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