Mortality limits used in wind energy impact assessment underestimate impacts of wind farms on bird populations

Peter Schippers*, Ralph Buij, Alex Schotman, Jana Verboom, Henk van der Jeugd, Eelke Jongejans

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The consequences of bird mortality caused by collisions with wind turbines are increasingly receiving attention. So-called acceptable mortality limits of populations, that is, those that assume that 1%–5% of additional mortality and the potential biological removal (PBR), provide seemingly clear-cut methods for establishing the reduction in population viability. We examine how the application of these commonly used mortality limits could affect populations of the Common Starling, Black-tailed Godwit, Marsh Harrier, Eurasian Spoonbill, White Stork, Common Tern, and White-tailed Eagle using stochastic density-independent and density-dependent Leslie matrix models. Results show that population viability can be very sensitive to proportionally small increases in mortality. Rather than having a negligible effect, we found that a 1% additional mortality in postfledging cohorts of our studied populations resulted in a 2%–24% decrease in the population level after 10 years. Allowing a 5% mortality increase to existing mortality resulted in a 9%–77% reduction in the populations after 10 years. When the PBR method is used in the density-dependent simulations, the proportional change in the resulting growth rate and carrying capacity was species-independent and largely determined by the recovery factor (Fr). When Fr = 1, a value typically used for robust populations, additional mortality resulted in a 50%–55% reduction in the equilibrium density and the resulting growth rate. When Fr = 0.1, used for threatened populations, the reduction in the equilibrium density and growth rate was about 5%. Synthesis and applications. Our results show that by allowing a mortality increase from wind farm collisions according to both criteria, the population impacts of these collisions can still be severe. We propose a simple new method as an alternative that was able to estimate mortality impacts of age-structured stochastic density-dependent matrix models.

Original languageEnglish
JournalEcology and Evolution
DOIs
Publication statusE-pub ahead of print - 4 Jun 2020

Keywords

  • bird mortality
  • collisions
  • Ornis 1% mortality criterion
  • population viability
  • potential biological removal
  • threshold assessment methods
  • wind farm

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