When a wind farm adopts a curtailment strategy to safeguard bats, it illustrates the effectiveness of this method beyond the usual before-and-after narrative. The Casselman Wind Project in Somerset County, Pennsylvania, led the way in evaluating this by modifying turbine operations corresponding to wind speed thresholds to diminish bat fatalities. This technique, examined by Edward Arnett and Michael Schirmacher, involved alternating turbine settings nightly between standard operation and elevated cut-in speeds of 5.0 or 6.5 meters per second.
The outcomes from their 2008 research revealed that curtailment considerably lowered bat fatalities. While 32 bat carcasses were noted, a thorough analysis indicated that 23 were found on nights when turbines operated at full capacity, while only nine were recorded on curtailed nights, suggesting the effectiveness of curtailment. By curtailing turbine operations, bat deaths were limited to fewer nights, potentially decreasing fatalities by 72 to 82 percent during turbine activity. The study’s methodology, which compared the same turbines under varying conditions nightly, confirmed that curtailment was genuinely effective rather than coincidental.
This method is not exclusive to Pennsylvania; consistent findings across numerous North American wind facilities support its success. A meta-analysis by Michael Whitby and his team identified a general pattern: each 1.0 ms−1 rise in curtailment wind speed results in a 33% decline in bat fatalities, with certain sites witnessing reductions as high as 62% at 5.0 ms−1.
Curtailment is not a comprehensive solution, as indicated by findings from places like an Australian wind farm where minor modifications in cut-in speed led to significant reductions in bat mortality without major revenue loss. Nevertheless, it is a robust mitigation strategy that can considerably decrease risks across various locations and species.
This nuanced perspective emphasizes that curtailment is not merely an all-or-nothing approach. The focus should be on how much exposure was mitigated, rather than solely on the fixed count of fatalities. Curtailment embodies a careful balance between operational effectiveness and wildlife preservation, advocating for genuine recognition of its accomplishments while acknowledging its constraints.