Forest Insects and Climate Change

Abstract

Purpose of Review Climate change affects populations of forest insect pests in a number of ways. We reviewed the most recent literature (2013-2017) on this subject including previous reviews on the topic. We provide a comprehensive discussion of the subject, with special attention to insect range expansion, insect abundance, impacts on forest ecosystems, and effects on forest insect communities. We considered forest insects according to their major guilds and biomes. Recent Findings Effects of climate change on forest insects are demonstrated for a number of species and guilds, although generalizations of results available so far are difficult because of species-specific responses to climate change. In addition, disentangling direct and indirect effects of climate change is complex due to the large number of variables affected. Modeling based on climate projections is useful when combined with mechanistic explanations. Summary Expansion of either the true range or the outbreak range is observed in several model species/groups of major insect guilds in boreal and temperate biomes. Mechanistic explanations are provided for a few species and are mainly based on increase in winter temperatures. In relation to insect abundance, climate change can either promote outbreaks or disrupt trophic interactions and decrease the severity of outbreaks. There is good evidence that some recent outbreaks of bark beetles and defoliating insects are influenced by climate change and are having a large impact on ecosystems as well as on communities of forest insects.

Complex responses of global insect pests to climate warming

“…; Pureswaran et al . ), as is the case for O brumata (WebTable 1). However, pests in annual and perennial systems might differ in their general susceptibility to phenological mismatching, with pests in annual systems possibly more sensitive to phenological host limitation, especially compared to bark beetles and root feeders.…”

“…; Pureswaran et al . ), climate modeling projections (Bellard et al . ), or some combination of these approaches (Sutherst et al .…”

“…For example, one common assumption of pest-response research is that climatic limiting factors, such as temperature or water availability, are constant across a species' geographic range (Grayson and Johnson 2018). As a result, studies often ignore intraspecific differences, a well-known source of variability in pest responses to climate change (Moran and Alexander 2014;Pureswaran et al 2018). Also, pest ranges generally span multiple environments that often include various types of managed landscapes (Tscharntke et al 2012), forming complex dynamic matrices of pest-ecosystem interactions (Bebber et al 2013;Karp et al 2018).…”

How do herbivorous insects respond to drought stress in trees?

“…Direct effects of warmer temperatures on insect physiology include rapid insect development and growth and increased survival rates through winter (Bale et al ., ). There is good evidence that global warming can promote insect outbreaks, but warm temperatures can also disrupt diapause requirements and spring development rates for temperate insects, leading to a decrease in outbreak severity (Pureswaran, Roques & Battisti, ).…”

Interactive Effects of Tree Mixing and Drought on a Primary Forest Pest

“…Beyond their direct effects on forest decline, both climate and tree diversity changes can have indirect effects on forest conditions through consequences on pest population dynamics and damages. Warmer conditions are likely to favor poikilothermic organisms like insects, resulting in more generations per year, higher fecundity and survival, thus leading to increased probability of outbreaks (Pureswaran et al, 2018;Jactel et al, 2019). Water stressed trees are also often more exposed to damage by serious forest pests like bark beetles and insect defoliators (Jactel et al, 2012.…”