the wind energy industry to reduce other forms of uncertainty in the
models. Wind energy currently represents approximately 5% of electric-
ity generation in Canada and U.S.A., with a target of increasingto 20% by
2025 in Canada and by 2030 in U.S.A (American Wind Energy
Association, 2016; Canadian Wind Energy Association, 2016). Installed
capacity increased by over 5100 MW (a 7% increase from 2014 installed
capacity) in 2015 alone (American Wind Energy Association, 2016;
Canadian Wind Energy Association, 2016). With more turbines and no
reductions in fatality rates at wind energy facilities, we expect fatalities
and species-level impacts to migratory bats to increase (i.e., greater de-
clines in N). Future modeling efforts should explore the impact of in-
creased turbine development and assessment of how mitigation
efforts can be applied to reduce population-level impacts.
The only method documented to reduce fatalities at wind turbines is
limiting operation during high risk periods, such as nocturnal periods of
low wind speeds during autumn migration (Arnett et al., 2011;
Baerwald et al., 2009). Such operational curtailment can reduce bat fa-
talities by 44–93% with minimal impact on power generation (Arnett
et al., 2011). The American Wind Energy Association recently adopted
policies to limit blade movement in low wind speeds as a voluntary op-
erating protocol to reduce fatalities (American Wind Energy
Association, 2015). Industry-wide implementation of operational miti-
gation or emerging technologies (e.g. acoustic deterrents; Arnett et al.,
2013) may be necessary to successfully manage migratory bat
populations and ensure stable and viable populations in North America.
Siting wind energy facilities in places perceived as lower risk for causing
bat fatalities could also help reduce impacts, although further research
is needed to determine the efﬁcacy of predicting risk from pre-siting
assessments (Baerwald and Barclay, 2009; Hein et al., 2013; Lintott
et al., 2016).
Conservation decisions must often be made with imperfect knowl-
edge and data gaps. We lack empirical data on population sizes and
trends for hoary bats and other migratory bat species, and given the
ecology of these species and technologies available, we are unlikely to
collect empirical population data in the near future. Our analyses sug-
gest there is a range of realistic possibilities for the impact of fatalities
from wind turbines that includes substantial population declines and
increased risk of extinction. The magnitude of these predicted impacts
may warrant re-evaluation of thestatus of hoary batsfrom least concern
to a threatened category on the IUCN Red List (IUCN, 2012). Given the
possibility for near or total extinction from wind-energy-related fatali-
ties, our results suggest that conservation planning to manage migrato-
ry bat populations should include actionsto reduce bat fatalities at wind
energy facilities in North America.
We thank Todd Katzner and two anonymous reviewers for com-
ments on the manuscript. Robyn Niver, Lori Pruitt, and Dan Nolﬁ
helped with designing and conducting the elicitation workshop
andprovidedcommentsonearlierdrafts. David Nelson and Ste-
phen Keller provided information to experts during the introducto-
ry phase of the elicitation workshop. Taal Levi, Ed Arnett, Paul
Cryan, and Maarten Vonhof contributed to earlier versions of the
modeling effort. The ﬁndings and conclusions in this article are
those of the authors and do not necessarily represent the views of
the U.S. Fish and Wildlife Service. USFWS, Region 3, provided travel
to the elicitation workshop. WFF was supported on NSF DEB-
1115895/1336390. RMRB is supported by Natural Sciences and En-
gineering Research Council of Canada.
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