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Alternating electric currents generate electromagnetic field. Power lines are highly observable sources of these artificial electromagnetic fields (EMF). SEA (2004) identified four potential sources of EMF associated with wind farming: the grid interconnection power line, the wind turbine generators, electrical transformers and the underground collector network cabling. Bansal et al. (2002) indicated that the wind turbine towers also can cause electromagnetic interference (EMI) on the performance of the nearby transmitters or receivers (Patel 1999). The EMI nearby transmitters or receivers can have hazardous effects on organisms. Koops (2000) calculated that a monopolar cable carrying 1500 A produces a magnetic flux density of approximately 300 μT on the seabed above the cable, falling off to 50 μT at a distance of 5 m above the seabed, and 13 μT at 20 m above the seabed.
Figure 1. The left map indicates the Samandağ and extended beaches (TR-H-1, TR-H-2, TR-H-3, Kale), the right map indicates sections of Samandağ beach.
Samandağ beach is located in the southern part of the Turkey, on the eastern Mediterranean (Fig. 1). The main beach is ~14 km and the extended beach is about 24 km in length. The beach width varies between 50 and 250 m in different parts of the beach. Two sea turtle species, Caretta caretta and Chelonia mydas, use the beaches as nesting habitat. Samandağ beach is one of the most important nesting beaches for green turtles in Mediterranean. The nest number of green turtles in this area has reached 621 in 2009 nesting season (Yalçın-Özdilek & Sönmez 2011). The River Asi separates the beaches into two sections, Meydan Beach on the south and the Çevlik and Şeyhhızır beaches on the north. Green turtles nest particularly about 3 km north and south of the Asi River mouth. Moreover, there is some evidence that that the area also serves as foraging habitat for sea turtles (Yalçın-Özdilek & Sönmez 2007; Yalçın-Özdilek & Auregi 2006).
The high wind energy potential of some locations in Turkey has encouraged private firms to attempt installing wind power plants. Samandağ has one of the most important wind energy potentials in Turkey (EİE 2010). To date, there are two licensed wind energy plants in Samandağ. One of the turbine fields is located about 250 m from the sea turtle nesting beach. Currently, there are 28 new applications for renewable wind energy plants in Samandağ, including one application for a 33-unit turbine field, producing 165 MW of power, located nearshore near the three km zone around the Asi river (Fig. 1) that has the highest density of nesting (RTEMRA 2012). Although the protected areas of Samandağ beach include the dune and open sandy zones, the planned positions of the turbines are just off the beach, in the nearshore area, where nesting females and hatchling have to traverse to get on and/or off the nesting area of Samandağ. Concerns related to the proposed wind plants have been discussed in different platforms with broad participation of academics and official decision makers and NGOs. The remarks put forward by academics in the meetings have been fruitful and drawn attention to the issue.
Here we address the potential threats to sea turtles from both the wind turbines and the cables that carry energy from the turbines. Using an electromagnetic meter to measure EMF in different locations around a turbine and its cable, we found generally that EMF values decreased with distance from the turbine, except for a corridor where the energy transfer cable is located one meter under the ground (Fig. 2).
Figure 2. The measured electromagnetic field around a wind turbine, located in the centre of the circle. Small circles indicate the measurement points.
Based on our measurements, the cables leaving from the wind turbines have stronger EMF values and thus may have possible negative consequences for sea turtles (Fig. 2), particularly if cables on or under the sea floor also generate large EMF values. Sea turtles often display strong migratory behaviour between foraging and breeding grounds, including loggerheads and green turtles (e.g. Carr 1975; 1986; Limpus et al. 1992). Loggerhead hatchlings leave nests in the northwestern Atlantic follow the Gulf Stream across to the northeastern Atlantic, and migrate back as large juveniles to the northwestern Atlantic (Bolten et al. 1998). Experimental studies show that hatchlings and juvenile turtles are sensitive to the earths natural magnetic field and they can distinguish magnetic inclination in different places during their migration routes (Lohmann 1991; Luschi et al. 2007). The magnetic field intensity varies in different parts of the earth and this is a potential source for positional information. Sea turtle can distinguish magnetic differences lighter than 9 mT (Lohmann et al. 1999; 2001). Therefore, the changes to electromagnetic fields in natural habitats from under sea or under sand cables with respect to impacts on the behaviour of sea turtles should be considered and investigated.
Hepbaşlı et al. (2001) ranked WEPs as potentially important future energy sources in Turkey, yet did not adequately consider the potential negative impacts of WEPs on the environment. The benefits of WEPs include low carbon emissions, being derived from a renewable source (wind), and being local. However, WEPs may have possible negative impacts, particularly on migrating animals such as sea turtles. Therefore, construction of these kinds of energy requires careful consideration, particularly in areas with high levels of biodiversity. The development of wind farms in Samandağ, which is one of the most important green turtles nesting beaches in the Mediterranean, should be assessed on site-specific and species-specific criteria to determine whether the adverse impacts can be mitigated. From an ecological point of view, coastal areas in Samandağ are fragile ecosystems with high ecological and biodiversity values, including sea turtles. According to the Bern Convention, endangered species such as sea turtles should be afforded primary protection. The Ministry of Forestry and Water Affairs of Turkey has invested time and energy with university researchers to protect nesting sea turtles in Samandağ. The protection of endangered species individuals is important, however in terms of conservation, the protection of a population, including its various habitats used for nesting, feeding, migration and wintering is critical for success. The protection of habitats in turn provides umbrella protection for larger ecosystems that are used by various flora and fauna. Therefore, we recommend that more effort is expended to protect all life stages and habitats of sea turtles, thereby conserving larger ecosystems on which many species depend.
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