Late Glacial and Holocene records of tree-killing conifer bark beetles in Europe and North America: Implications for forest disturbance dynamics

Abstract

Outbreaks of conifer bark beetles in Europe and North America have increased in scale and severity in recent decades. In this study, we identify existing fossil records containing bark beetle remains from the end of the Last Glacial Maximum (~14,000 cal. yr BP) to present day using the online databases Neotoma and BugsCEP and literature searches, and compare these data with modern distribution data of selected tree-killing species. Modern-day observational data from the Global Biodiversity Information Facility (GBIF) database was used to map recorded distributions from AD 1750 to present day. A total of 53 fossil sites containing bark beetle remains, from both geological and archeological sites, were found during our searches. Fossil sites were fewer in Europe ( n = 21) than North America ( n = 32). In Europe, 29% of the samples in which remains were found were younger than 1000 cal. yr BP, while in North America, remains were mainly identified from late Glacial (~14,000–11,500 cal. yr BP) sites. In total, the fossil records contained only 8 of 20 species we consider important tree-killing bark beetles in Europe and North America based on their impacts during the last 100 years. In Europe, Ips sexdentatus was absent from the fossil record. In North America, Dendroctonus adjunctus, Dendroctonus frontalis, Dendroctonus jeffreyi, Dendroctonus pseudotsugae, Dryocoetes confusus, Ips calligraphus, Ips confusus, Ips grandicollis, Ips lecontei, Ips paraconfusus, and Scolytus ventralis were absent. Overall, preserved remains of tree-killing bark beetles are rare in the fossil record. However, by retrieving bulk material from new and existing sites and combining data from identified bark beetle remains with pollen, charcoal, tree rings, and geochemistry, the occurrence and dominance of bark beetles, their outbreaks, and other disturbance events can be reconstructed.

Tracking fire activity and post-fire limnological responses using the varved sedimentary sequence of Lake Jaczno, Poland

“…Although not investigated on a large scale, fire likelihood and severity can be increased by insect outbreaks (Rogers et al, 2020) because changing fuel conditions through, for example, defoliation negatively affects timber and fiber production or changes the tree water budget (Schafstall et al, 2020). Beetle-induced changes to foliar moisture have the greatest effects on flammability (Fettig et al, 2021).…”

Meteorological and climatological triggers of notable past and present bark beetle outbreaks in the Czech Republic

“…For example, Schafstall et al (2022) found only three main bark beetle outbreaks between 1400 BP and the present in the High Tatras (Slovakia) (the last one post-2004 after the disas-trous windstorm Elizabeth of 19 November 2004), in which Ips typographus was rather low in numbers. Moreover, bark beetles remain rather neglected in palaeoecology with only a few dozen reported sites in Europe for the whole of the Holocene (Schafstall et al, 2020).…”

Interacting effects of fire and hydroclimate on oak and beech community prevalence in the southern Great Lakes region

“…However, pests and pathogens are difficult to detect using traditional palaeoecological approaches, such that even in ecosystems with regular insect outbreaks (e.g. bark beetles), the outbreaks can only be detected through indirect means (Morris & Brunelle, 2012) or at small forest hollow sites (Schafstall et al., 2020). Hence, whether pests and pathogens had any effect on American beech dynamics during the Holocene remains possible but unknown and unstudied.…”