Unstated impacts of the green energy industry on the habitat of a coastal delphinid: Turbid-turbulent wakes induced by offshore wind turbine foundations

Abstract

  1. Offshore wind farms (OWFs) are a green energy solution to reducing CO2 emissions, but often encroach on major habitats of coastal delphinids. Clustered OWF construction in shallow waters may have cumulative negative impacts on coastal delphinids and marine ecosystems. Although the impacts of piling noise have been discussed extensively, the potential impacts of oceanographic alterations induced by wind turbine foundations are rarely discussed.
  2. Two OWFs were constructed near the core habitat of a critically endangered subspecies of humpback dolphin (Sousa chinensis taiwanensis) in the eastern Taiwan Strait. Turbid-turbulent wakes induced by wind turbine foundations were inspected using Landsat images. Sighting rates of the humpback dolphin that were obtained from boat-based line-transect surveys near the northern OWF (OWFn) since the late 2000s were examined.
  3. Indicators of surface turbidity were used to highlight turbid-turbulent wakes extending in the direction of the main current. Sighting rates of the humpback dolphins near the OWFn have been declining since the 2000s, but decreased significantly after the OWFn was constructed and began operating.
  4. The long-term decline in sighting rates implies an alarming decline in the population size of humpback dolphins. Decreased sighting rates after the OWFn installation indicate the reduced utilization of a once-important habitat. Offshore wind farm construction may influence prey abundance and composition and cause acute stress from piling noise; operational noise may mask the chorus of prey fish and turbid-turbulent wakes may disturb the benthic ecosystem.
  5. Site selection committees for future OWFs should avoid the habitats of coastal delphinids and areas subject to strong ocean currents. Ecological impact assessments for OWF projects should examine the impacts of turbulent wakes on benthic ecosystems and of acoustic disturbance on marine mammals. Long-term environmental monitoring programmes are recommended, which can be funded by wind energy companies as a compensatory measure.