Responses of tree-killing bark beetles to a changing climate

• Author(s) / Creator(s)

  • Raffa, Kenneth F.
  • Aukema, Brian H.
  • Bentz, Barbara J.
  • Carroll, Allan L.
  • Hicke, Jeffrey A.
  • Kolb, Thomas E.

• Bark beetles cause widespread tree mortal- ity, so understanding how climate change will infl uence the distribution and magni- tude of outbreaks by this group of herbi- vores is important. We fi rst develop a framework of outbreak dynamics that emphasizes transitions from states domi- nated by negative feedback to those dominated by positive, density-dependent feedback. We then consider mechanisms by which temperature and precipitation changes can allow populations to breach critical thresholds, and the empirical data relating outbreaks to weather. Finally, we consider how anticipated climatic change, and relationships with new hosts and natu- ral enemy guilds, may infl uence dynamics in new habitats. Th ere is strong evidence that elevated temperature can increase over- wintering survival and decrease generation times of bark beetles, although evolved traits can also constrain response to warming in some habitats. Moreover, combinations of phenotypic plasticity, geno- typic variation and physiological thresholds yield a broad range of conditions under which adults emerge synchronously, and thus can mass attack trees. Th ere is likewise strong evidence that severe drought reduces tree defences against attack. Drought stress can occur through lower precipitation and/ or higher temperatures that reduce soil moisture and/or raise vapour pressure defi - cit. We also delineate three categories of range modifi cations: increased and more persistent establishment in areas where trees experienced only intermittent expo- sure historically; establishment in areas dominated by host species but where local populations experienced little or no pres- sure historically; and movement into new areas containing susceptible species that have not been exposed previously. Each of these has been documented for bark beetles. Trees in areas that experienced minor or no exposure generally had lower defences than their more historically exposed counter- parts. However, there can be lags in beetle behavioural responses. In some cases, more heterogeneous forest structure, more abun- dant local predators and competitors and low host nutritional quality could poten- tially lessen risk in new habitats. Direct comparative studies are needed to evaluate outbreak potentials following range expan- sions driven by climate warming.

• Date created

  2015

• Subjects / Keywords

  • Biosphere
  • Life
  • Arthropoda
  • Insects
  • Entomology

• Type of Item

  Chapter

• DOI

  https://doi.org/10.7939/r3-yvpw-pz59

• License

  © CAB International 2015. All rights reserved. No part of this publication may be reproduced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners.