Forest insects and climate change: long‐term trends in herbivore damage

Abstract

Long-term data sets, covering several decades, could help to reveal the effects of observed climate change on herbivore damage to plants. However, sufficiently long time series in ecology are scarce. The research presented here analyzes a long-term data set collected by the Hungarian Forest Research Institute over the period 1961–2009. The number of hectares with visible defoliation was estimated and documented for several forest insect pest species. This resulted in a unique time series that provides us with the opportunity to compare insect damage trends with trends in weather patterns. Data were analyzed for six lepidopteran species: Thaumetopoea processionea, Tortrix viridana, Rhyacionia buoliana, Malacosoma neustria, Euproctis chrysorrhoea, and Lymantria dispar. All these species exhibit outbreak dynamics in Hungary. Five of these species prefer deciduous tree species as their host plants, whereas R. buoliana is a specialist on Pinus spp. The data were analyzed using general linear models and generalized least squares regression in relation to mean monthly temperature and precipitation. Temperature increased considerably, especially over the last 25 years (+1.6°C), whereas precipitation exhibited no trend over the period. No change in weather variability over time was observed. There was increased damage caused by two species on deciduous trees. The area of damage attributed to R. buoliana decreased over the study period. There was no evidence of increased variability in damage. We conclude that species exhibiting a trend toward outbreak-level damage over a greater geographical area may be positively affected by changes in weather conditions coinciding with important life stages. Strong associations between the geographical extent of severe damage and monthly temperature and precipitation are difficult to confirm, studying the life-history traits of species could help to increase understanding of responses to climate change.

Weather-dependent fluctuations in the abundance of the oak processionary moth, Thaumetopoea processionea (Lepidoptera: Notodontidae)

“…The infl uence of average temperature in the different time windows recorded in this study differs from that previously reported (Wagenhoff & Veit, 2011;Klapwijk et al, 2013). The highest explanatory power was recorded for the May to July period.…”

“…Climate change therefore may for example cause range expansion (Vanhanen et al, 2007;Battisti, 2008;Jepsen et al, 2008;Battisti & Larsson, 2015;Battisti et al, 2017), either decrease or increase the number of generations in multivoltine species (Ayres & Lombardero, 2000;Jöns-son et al, 2009) and alter their interactions with their host plants (Pelini et al, 2009;Robinet & Roques, 2010) and natural enemies (Jeffs & Lewis, 2013;Kalinkat & Rall, 2015). The summation of these different effects can have a signifi cant effect on population fl uctuations, outbreaks and damage by forest insects (Mattson & Haack, 1987;Leskó et al, 1995Leskó et al, , 1998Csóka, 1997;Rouault et al, 2006;Dobbertin et al, 2007;Jactel et al, 2012;Klapwijk et al, 2013;Hlásny et al, 2015). the population fl uctuations, as already suggested in several earlier papers (Klapwijk et al, 2013;Wagenhoff & Veit, 2011;Wagenhoff et al, 2013Wagenhoff et al, , 2014.…”

“…Taking April temperature into account only had a signifi cant effect at one of the three locations (Acsád). Therefore, we excluded it, although several papers (Wagenhoff & Veit, 2011;Meurisse et al, 2012;Klapwijk et al, 2013) mention that early spring (March and April) temperatures may infl uence populations due to their direct effect on larval survival and in disrupting the synchrony between budburst and egg hatch. However, the effect of this desynchronization is quite plastic, since young larvae may survive 2-3 weeks of starvation (Wagenhoff et al, 2013) and bud burst occurs earlier following mild winters and in warm early springs (Wagenhoff et al, 2014).…”

“…The summation of these different effects can have a signifi cant effect on population fl uctuations, outbreaks and damage by forest insects (Mattson & Haack, 1987;Leskó et al, 1995Leskó et al, , 1998Csóka, 1997;Rouault et al, 2006;Dobbertin et al, 2007;Jactel et al, 2012;Klapwijk et al, 2013;Hlásny et al, 2015). the population fl uctuations, as already suggested in several earlier papers (Klapwijk et al, 2013;Wagenhoff & Veit, 2011;Wagenhoff et al, 2013Wagenhoff et al, , 2014. We assume that high spring temperatures have positive effects on the populations as under these conditions development is faster and mortality lower.…”

Forest Insects and Climate Change

“…Long-term surveys and examination of outbreak dynamics of five species of European Lepidoptera between 1800 and 2011 revealed climate-driven changes in outbreak severity, cyclicity, and frequency, but there were mixed effects of temperature on outbreak activity [12,26,27]. It is often argued that the frequency and severity of C. fumiferana outbreaks in North America have increased in the twentieth century.…”