Consequences of Climate Warming and Altered Precipitation Patterns for Plant-Insect and Multitrophic Interactions
Year: 2012
Type: review
Abstract: Understanding and predicting the impacts of anthropogenically driven climate change on species interactions and ecosystem processes is a critical scientific and societal challenge. Climate change has important ecological consequences for species interactions that occur across multiple trophic levels. In this Update, we broadly examine recent literature focused on disentangling the direct and indirect effects of temperature and water availability on plants, phytophagous insects, and the natural enemies of these insects, with special attention given to forest ecosystems. We highlight the role of temperature in shaping plant and insect metabolism, growth, development, and phenology. Additionally, we address the complexity involved in determining climate-mediated effects on plant-insect and multitrophic level interactions as well as the roles of plant ecophysiological processes in driving both bottom-up and top-down controls. Climate warming may exacerbate plant susceptibility to attack by some insect groups, particularly under reduced water availability. Despite considerable growth in research investigating the effects of climate change on plants and insects, we lack a mechanistic understanding of how temperature and precipitation influence species interactions, particularly with respect to plant defense traits and insect outbreaks. Moreover, a systematic literature review reveals that research efforts to date are highly overrepresented by plant studies and suggests a need for greater attention to plant-insect and multitrophic level interactions. Understanding the role of climatic variability and change on such interactions will provide further insight into links between abiotic and biotic drivers of community- and ecosystem-level processes. Anthropogenic activities have led to rapid and unprecedented increases in atmospheric carbon dioxide (CO2) and other greenhouse gases, which in turn have resulted in numerous observable climatic changes, such as elevated temperature, increased frequency and severity of extreme weather events (e.g. heat waves and droughts), and altered precipitation patterns (e.g. decreased snow cover) (National Research Council, 2010). Species are responding to these climate change factors, as demonstrated by shifts in phenology (the timing of key biological and life history events), biogeographic ranges, and ecological interactions (Bale et al., 2002; Parmesan and Yohe, 2003; Hegland et al., 2009; Robinson et al., 2012). In this Update, we review and discuss the consequences of climate change on plant-insect and multitrophic interactions. Specifically, we address the direct and indirect effects of climate warming and altered precipitation patterns on plants, phytophagous insects, and higher trophic level organisms. We focus on these two components of climate change, firstly, because temperature is the abiotic factor that most directly influences insects (Bale et al., 2002), and secondly, because water availability plays a prominent role in mediating plant-insect interactions (Mattson and Haack, 1987; Huberty and Denno, 2004). Moreover, heat and drought are often interconnected climatic stressors. While other global change drivers, such as elevated CO2 and ozone, also have significant consequences for plant-insect and multitrophic interactions, those effects are beyond the scope of this Update and have been have been recently reviewed elsewhere (e.g. Lindroth, 2010; Robinson et al., 2012). Over the last century, average global surface air temperatures have increased by 0.81°C, and climate models project an additional 1.1°C to 6.4°C increase by the end of the 21st century, with stronger warming trends in terrestrial habitats and at higher latitudes (see National Research Council, 2010 and references therein for observed and predicted patterns discussed here). In addition to elevated mean temperatures, climate models predict an increase in the frequency and intensity of extreme warming events, such as heat waves. Beyond these global warming trends, climate change patterns demonstrate strong seasonal and regional signals. For example, mean winter temperatures in the Midwest and northern Great Plains of the United States have increased by 4°C over the past 30 years. Compared with temperature, observations for precipitation are more variable, demonstrating mean annual increases as well as decreases at regional scales and across seasons. In general, climate model predictions for changes in precipitation are more uncertain than for temperature. However, some specific projections related to precipitation are considered to be robust, including expected increases in the total area of land affected by drought, the number of dry days annually, and the risk of drought in snowmelt dominated ecosystems. Globally, the land area affected by drought has doubled since 1970, according to historical Palmer Drought Index data. Decreased snowpack is also a well-established consequence of global climate change, and many mid- to high-latitude regions are experiencing earlier snowmelt compared with historical averages: up to 20 d earlier in the western United States. Early snowmelt, coupled with warmer summer temperatures, is predicted to decrease summer water availability in regions dominated by snowmelt (e.g. the U.S. Intermountain Region). The effects of climate change on plants and insects can be direct, resulting from modifications in climate-sensitive plant and insect traits, or indirect, resulting from climate-induced changes in their reciprocal partners and/or higher trophic level organisms, such as predators, parasitoids, or pathogens of insects (Fig. 1). We consider both direct and indirect effects here because they can be difficult to disentangle and because their interactions can be important. The composite effect of climate change on plants and insects reflects some combination of individual direct and indirect effects on interacting species. Thus, in some cases, it is not appropriate to disassociate these effects. In this Update, we address (1) direct and herbivore-mediated effects on plants, (2) direct and plant-mediated effects on herbivores, and (3) effects on higher trophic-level organisms and multitrophic-level species interactions. Additionally, we review the state of scientific research on these topics, highlighting areas of research poorly represented in the literature and discuss the implications of climate change effects on species interactions for large-scale environmental change and ecosystem feedbacks. In addition to limiting this Update to climate warming and altered precipitation, we restrict our discussion to natural systems, with special attention to forest ecosystems. Key traits and processes underlying the response of plants, insect herbivores, and higher trophic level organisms to climate change. Solid arrows represent direct effects of climate change on species traits (in boxes). Dashed arrows represent indirect effects resulting from altered trophic interactions (traits along arrows). The gray box highlights indirect effects that can influence species interactions between and across trophic levels. At the organismal level, direct effects are driven by modifications in climate-sensitive metabolic and physiological processes. At the population level, altered mortality and reproduction due to climate change can affect population growth and drive evolutionary change. At the community level, shifts in spatial and temporal distributions of interacting species may alter resource availability and quality for consumers and top-down controls on plant productivity. In turn, these direct and indirect effects may lead to cascading and feedback effects on ecosystem level traits, including carbon sequestration and net ecosystem production. This Update article is not an exhaustive review. Rather, it aims to provide a broad, hierarchical overview, which highlights some of the observed and potential ecological consequences of climate warming and altered precipitation patterns on plant-insect and multitrophic species interactions. Consistent with the intended purpose of Update articles to provide a topical summary that is accessible to a broad audience, including students and researchers, we present an introduction to key traits and processes important for understanding plant-insect and multitrophic interactions with respect to climate change. Our primary goal is to identify major pathways and feedbacks by which trophic interactions can mediate plant and insect responses to climate warming and altered precipitation, namely, increased drought frequency and/or intensity. The principal effects of climate warming on plants include modification of physiological processes, growth, development, reproduction/mortality, and phenology (Fig. 1). For example, temperature is a key factor controlling plant phenology, and elevated temperatures are expected to advance important phenological stages. In trees, the critical springtime period of budbreak and leaf expansion is cued by both photoperiod and temperature (van Asch and Visser, 2007). Genetically determined differences in budbreak phenology among tree species (i.e. early and late developers) are linked to photoperiod. Within species, however, budbreak is temperature dependent. Upon receiving sufficient winter chilling, buds shift from a dormant phase to a developmental phase, and maturation is strongly temperature dependent thereafter. Timing of budbreak is not only a critical developmental trait for plants, but also an important trait influencing food availability and quality for a number of phytophagous insects. The major physiological processes (e.g. respiration and photosynthesis) influencing plant growth are also temperature sensitive, but differentially so, both among species and plant functional groups (Tjoelker et al., 1999; Hanson et al., 2005; Rennenberg et al., 2006; Wang et al., 2012). Net photosynthesis (primary production) typically peaks within the range of normally experienced temperatures (Kirschbaum, 2000; Berggren et al., 2009), which as described in the following section, is a key difference with respect to insect herbivores. By increasing net photosynthesis and extending the growing season, warmer temperatures tend to accelerate plant growth. At middle to high latitudes, plant growth rates generally increase with temperature (Norby and Luo, 2004). Likewise, a meta-analysis of plant response to experimental warming revealed that productivity increased with temperature, especially in high latitude sites (Rustad et al., 2001). Growth enhancement may be reduced, however, if respiration increases more strongly than does photosynthesis, in particular under conditions of heat and drought stress (Rennenberg et al., 2006; Berggren et al., Moreover, the net effect of changes in growth also on physiological such as temperature of leaf which among species and functional groups (Tjoelker et al., 1999; Hanson et al., 2005; Rennenberg et al., Thus, climate warming may in or effect on forest on individual species responses under climate change as well as interacting climate change (Kirschbaum, In the effects of warming may on water availability. dry drought insect and mortality et al., et al., Moreover, temperature and precipitation can in For example, reduced snow from both winter drought and temperatures can in events and tree mortality due to water stress summer et al., 2012). the and timing of changes in temperature and precipitation are critical for plant growth, and the of plants as food for phytophagous insects. influences not only the but also the quality of primary production. In trees, the period of leaf and expansion is by and with increasing and and and Thus, leaf maturation may of availability for herbivores. also quality of effects on leaf meta-analysis by and revealed that both and tend to under elevated temperatures, are on demonstrating that the quality of plant for phytophagous insects will change with climate water availability influences plant quality for and can differentially affect insect and Denno, 2004). Drought to of and in of plants (Mattson and Haack, 1987; et al., warming will increase the frequency and intensity of drought events, studies the effects of temperature and water represent a critical area of is the impacts of elevated temperature on of in plants and to the and if (e.g. and are not photosynthesis to growth than and of of (e.g. and generally with but of typically increase and 2006; and In studies that have the effects of elevated temperature on plant that the effects may be species and/or For example, et that elevated temperatures decreased of and but not affect of in et that warming not affect but increase of in both and availability and drought stress can also influence of plant such as and changes in these also among species and in (Mattson and Haack, 1987; and et al., in response to temperature and water availability it difficult to predict how climate change will alter plant across species and ecosystems. The direct effects of climate change will influence not only plant to insect but also plant to insect However, research has the effects of climate change for plant traits (e.g. springtime of trees, such as growth rates et al., but climate change may alter plant and For example, et that have a high to and that under the combination of warmer temperatures and elevated than controls. elevated temperatures both increase net primary and the growing season, warming may the of plants to for if warming drought plants may be of Moreover, the direct and indirect effects of climate change on insects may affect the of plants community shifts in species or insect as well as changes in the of which lead to herbivore-mediated indirect climate change effects on plant the and of climate warming can directly affect the development, growth, and phenology of phytophagous insects (Fig. 1). metabolic rates are highly to temperature, with an increase of across the range of experienced temperatures (Bale et al., 2002; Berggren et al., to higher growth, and development, in turn, may lead to population increases reduced and decreased to natural Moreover, warmer and temperatures tend to insect (Bale et al., population have been to from a combination of and reduced For example, recent of and in western have been linked with altered life in particular changes in of annual related to climate warming et al., 2003; and In some cases, increased in response to high temperatures and precipitation, feedbacks between insect and to drive the abiotic to both recent climate history and climate models increases in climatic variability as well as elevated temperatures, the of critical insect population will increase in et al., to plants, insect phenology is cued by photoperiod and temperature (van Asch and Visser, 2007). For phytophagous insects at middle to high latitudes that in photoperiod is the major for of temperature is the primary for of (e.g. a of the effects of climate warming is earlier and of these insects. Climate warming the last which is rates of change, has to phenological in many insect species (Bale et al., 2002; Parmesan and Yohe, insect is more than plant to temperature insect may more strongly and/or than plant to climate warming (Bale et al., 2002; Berggren et al., 2009; The of phenological between insects and their plants is as of the most important potential consequences of climate change for plant-insect interactions (Bale et al., 2002; Parmesan and Yohe, This is especially for early insects, including some species such as forest and is linked to phenological with their plant et al., quality with maturation (i.e. and water and that and with early of leaf and expansion often have higher than those that in et al., and Climate warming and drought may also influence phytophagous insects changes in food including and traits that occur of phenology. warming to of but increase of in plant and 2006; and Likewise, drought can also increase and/or decrease (e.g. and Haack, 1987; and (e.g. et al., and other groups of defense Thus, warming and decreased water availability may alter the of plant-insect interactions that are by of for example, affect on and Lindroth, affect on and and affect on et al., The consequences of warming and drought stress on plant quality will influence the of insects, the and of responses will among and insect species et al., Huberty and Denno, et al., the direct and plant-mediated effects of climate change on insect growth and will alter to and defense natural enemies parasitoids, and Compared with plants and insect herbivores, these natural enemies may rates (e.g. growth, and of change in response to climate warming and altered precipitation Despite the of literature the effects of climate warming on plant and insect physiological processes, and phenology, research on climate change effects on higher trophic level organisms and multitrophic interactions is (see following This lack of is due in to the and of underlying indirect effects as well as the influence of such as temperature, on effects across trophic levels. phytophagous insects are by a of top-down (e.g. natural and bottom-up (e.g. plant availability and controls. to affect insect and population and and Moreover, climate-mediated effects on higher trophic level organisms can influence plant and ecosystem productivity trophic for example, the direct effects of and other on can lead to indirect effects on enemies (e.g. predators, parasitoids, and significant over the population of insect and species and et al., Climate change may have important direct and indirect effects on the phenology, and of these higher trophic level organisms (Fig. 1). For example, elevated temperatures may increase such as metabolic and developmental rates et al., to phytophagous insects, resulting in a greater number of temperature and water availability can influence such as the which is an important biotic et al., At higher trophic rates of change and of response may compared with insect species due to in of traits, such as or differences in et al., 2007). For example, a decrease in spatial between and as a of responses to which to increase availability and quality for higher trophic level organisms is dependent on insect response to climate change, which in turn may be affected by plant Thus, elevated temperatures and altered precipitation multitrophic interactions, in phenological Additionally, climate-induced changes in plant and can alter insect developmental rates and (e.g. or the availability and quality of food for and other (Mattson and Haack, 1987; Moreover, in some cases, the of insect is by their with and the of species can be by temperature and 2007). and on of plant to their insects. are considered to be indirect plant and of often increase in response to a number of biotic and abiotic and 2010). In response to by insects, plants can the of and/or of which is considered of plant can alter and direct and indirect effects on insect and/or natural elevated temperatures, plant can also higher of and rates et al., and 2010). However, the effects of climate warming on the and quality of and (i.e. plant on the effects of abiotic and biotic factors, including (1) interactions among climate change (e.g. water (2) plant traits (e.g. carbon and (3) attack (e.g. and of Thus, rates are expected to increase under climate drought, for example, may ecophysiological controls and et al., climate-induced changes in and may influence and as well as top-down controls on population and insect have to in some cases, defense in plant 2002; et al., The with these can for other biological including growth, and response and 2002; 2002; et al., Thus, the direct effects of climate change on plants may lead to indirect effects on insect as well as higher trophic levels. In insect that plant for their natural enemies may be affected by such indirect effects. For these species, plant can affect the of (e.g. and which can influence to (e.g. and susceptibility to (e.g. et al., For higher trophic level organisms, indirect effects of climate change may or the food multitrophic species interactions more and than plant-insect interactions. studies have the effects of temperature and water availability on multitrophic interactions from both bottom-up and top-down review research and in we a of of to identify and patterns in the number of studies on the discussed in this Update (Fig. literature the effects of climate warming on plants and insects has increased since the with to date to natural or forest that more than than the number of we to our by on the effects of climate warming on and natural development, growth, or phenology (see for We these (i.e. development, growth, or because they are traits for species across trophic levels. The most significant of our literature the strong research on plants, which for more than of our of literature effects of climate warming on plants, insects, and higher trophic level organisms. number of studies from to of and or and or and or or for individual trophic (1) plant (2) (3) insect and or insect and or or or of studies on (1) plants, (2) plant-insect interactions, and (3) higher trophic or multitrophic level interactions. the as those in the plant-insect interactions, which involved insect and of at the of research investigating effects on plants and insects in the of growth in does not to be driven by as only a of the studies in in rates have in the last from a to increase across trophic (Fig. The number of studies on insects and functional in to the number on plants, which is a difference insects represent a greater to than the number of compared with Moreover, in of the well-established ecological and of insect herbivores, research this functional a of the number of studies on insects of the research on plants, is greater than on plant-insect interactions, which in turn is greater than on higher trophic level organisms and/or multitrophic interactions (Fig. Despite growth in research biotic effects of climate is a in the consequences of climate change for species interactions across trophic including plant-insect and multitrophic level interactions. the of top-down controls for plant and insect and population as well as ecosystem it is important to how climate change may affect these of species interactions. In we that research on plant defense (i.e. both and and the role of these traits in mediating plant-insect and multitrophic level interactions be a area of especially given the potential for insect and species to drive large-scale ecological and environmental change in response to climate change. phytophagous insect will increase in due to development, increased and decreased mortality with climate which may lead to higher of plant in the however, individual plant and insect species may For example, et responses of and plant pathogens in response to which led to patterns among plant species. interactions between the and the of individual species may in plants are to a that often and large-scale environmental change et al., 2004). plants have insect herbivores, some insects, in particular some species, have that these plant For example, of herbivores, such as can to plant also of insect to temperatures (e.g. and Climate change, in particular increased drought can influence plant by insect herbivores, changes in plant water and et al., For example, drought stress has been to tree to in and et al., et al., and increase insect on a large-scale level in forest (e.g. et al., The underlying plant susceptibility to insect attack and mortality drought, however, poorly et al., number of have to how drought including that water stress plants to carbon due to metabolic and to et al., water is not temperatures can affect plant water by increasing the and (Kirschbaum, 2000; Hanson et al., 2005; et al., 2009), which may decrease carbon metabolism, and plant Likewise, interactions between precipitation and temperature can increase plant susceptibility to insect such as temperature increases drought stress or lack of snow and decreases or in et al., have important implications for interactions, and global and et al., 2009; et al., Globally, a number of plant species have experienced as a of drought, warmer temperatures, and/or the of insect and pathogens et al., 2003; et al., et al., Moreover, a number of studies that the frequency and severity of by some forest will in response to predicted climate change et al., 2003; et al., interactions that occur across trophic and predicted global environmental change may and natural which can lead to large-scale community environmental change, and ecosystem feedbacks et al., For example, of can carbon sequestration and alter other ecosystem processes et al., et al., both of which can increase the of outbreaks. Research investigating the consequences and feedbacks of climatic variability on plant-insect interactions at multiple of ecological from community to ecosystem is to predict large-scale environmental responses to climate change. In general, we have discussed climate warming and altered precipitation patterns from a broad in this how these climate will change in the and to influence ecological interactions is and more For example, studies to the influence of seasonal changes (e.g. summer within a and regional as temperature and water availability at these temporal and spatial scales to influence the growth, development, and phenology of organisms and ecological interactions among species. Likewise, consider and regional climate than global change and For some northern latitudes are expected to greater annual precipitation, summer water availability may decrease in Moreover, such changes in precipitation may be more important for plants compared with phytophagous insects or their natural of the role of climate variability on the and life history of organisms as well as the of species interactions can underlying responses to climate change. In addition to elevated temperature and altered precipitation a number of other global environmental change factors, including increased CO2 and biological change, and will also important roles in shaping plant-insect and multitrophic interactions. the interactions among these global environmental changes of the for number of for this such as or or and of response patterns and/or has and For example, warming may phenological response to climate change et al., and some to these provide the for determining (e.g. metabolic and physiological underlying in are well for broad patterns and but are to or can important drivers, especially in in which critical with et al., research are and of will be to our understanding of how climate change will affect species interactions in of the We two for and for this carbon dioxide
Source: PLANT PHYSIOLOGY
Language: English
Subfield: Insect Science
Domain: Life Sciences
SDGs: Life on land, Climate action
Open Access status: green
OpenAlex ID: W2150157967