Agricultural production depends heavily on climate variables, like temperature and water availability. Because insect pests are closely linked to these factors, short-term climatic extremes can have significant impacts on crop productivity.
Global warming is expected to increase pest populations, which could result in substantial economic losses for agriculture. Temperature changes influence phenology, particularly in univoltine species and those with shorter life cycles. Click Here to learn more about how to deal with pests.
Temperature
Depending on the species, temperature changes can dramatically affect the growth rate of pests. This is due to the metabolic and reproductive processes of insects being influenced by their thermal optimum. For instance, high temperatures accelerate insect metabolism and fecundity while low temperatures slow down these processes. Therefore, warmer climates can increase the number of generations per year, resulting in a rapid build-up of pest populations that threaten crops.
Temperatures also impact insect behavior and movement, causing them to move to new areas. For example, increased summer heat can cause a tree-feeding pest to move into a cropping region. Similarly, drought conditions can allow invasive plant pests to advance from incipient populations to epidemic status. These factors can be amplified through feedback mechanisms within the insect-host species complex, resulting in highly variable within-species responses to climate change.
Precipitation changes can also impact pests by influencing their habitats and water sources. In general, precipitation can lead to an expansion of the pest overwintering range or an increase in the breadth of their breeding and feeding habitats.
However, the impact of changing temperatures on pests is likely to be more dramatic because it can also affect the predatory capacity of a species. As temperature increases, the metabolic rate of predators decreases and their ability to kill pests deteriorates. This can reduce the impact of predators on pest populations and facilitate their spread and growth.
Scientists agree that climate change is causing shifts in the distribution of many pest species. However, it is still difficult to predict how and when these shifts will happen. To make these predictions, scientists need to understand how climate change impacts the geographic range of a pest species and identify the specific aspect of climate change that is altering its distribution. This involves developing mechanistic models that take into account factors like climatic variables, population dynamics, host plant traits, and anthropogenic disturbances. It also requires incorporating data at finer geographical scales. For example, incorporating the behavioral thermal regulation of microhabitats could help improve predictions by buffering temperatures from extremes, but this requires reliable daily data at the habitat scale.
Precipitation
In addition to temperature change, precipitation can also have a significant impact on pest populations. Precipitation can influence a pest species’ ability to persist in a region, or it may impact the duration and magnitude of an insect-borne disease outbreak.
Many major crop pests, such as aphids and whiteflies, are disease vectors that transfer viruses to crops that cause serious plant diseases. Climate change can affect the virulence of a virus, which can increase its transmission to new host plants or spread from an existing host population.
A change in the amount of available moisture can also affect pests, influencing their growth rate, fecundity, and mortality. If the available water supply decreases or becomes less uniform, pests can become more abundant in a given area, or they may be forced to move elsewhere to find sufficient water.
The recent desert locust outbreak in the Horn of Africa is an example of how a shift in weather patterns can lead to the rapid development of new and devastating pests that threaten global food security. Skyrocketing global trade and climate change will likely amplify native and invasive pest frequency, necessitating the need for adaptive measures to mitigate their adverse effects.
Climate change can also disrupt natural enemy dynamics, which can further exacerbate pest populations and reduce the effectiveness of control strategies. For example, a rise in temperatures can accelerate the phenological cycle of multivoltine insects, such as aphids and cabbage white butterflies, allowing them to have more yearly generations.
This phenological mismatch between pests and their natural enemies can debilitate biocontrol efforts and further enlarge pest populations, which in turn will lead to higher crop damage. The same effect can occur in the case of climate-mediated changes in resistance to insecticides. If pests can persist in new regions because of weather changes, they will also be able to build up resistance to the most common insecticides. As a result, the use of more effective and expensive resistance management tools will be necessary. This will inevitably increase the cost of food production.
Water Supply
Many crop pest species require a steady supply of water to grow and reproduce. Changes in temperature and precipitation can affect their ability to access this water, impacting the growth rates and emergence of populations. The frequency of extreme weather events, such as heat waves and heavy rains, is also changing globally and increasing in intensity.
Climate change alters the geographic distribution of insect pest species, moving them into regions they would not have occupied otherwise. This expansion of their habitats can cause problems in agricultural production by increasing the number of pests that threaten crops, as well as by allowing them to develop resistance to common pest control measures.
The increase in atmospheric carbon dioxide concentrations produced by human activity impacts the metabolism of insects, altering their growth rate and development. In addition, a rise in carbon dioxide levels affects the absorption of nutrients by plants, and this can influence the growth rate of crop pests as well.
Warming temperatures have an impact on the biological limits of insects, which are determined by the optimal temperature for their life cycle and behavior. Deutsch and colleagues studied these effects in models of insect population dynamics, factoring in metabolic and reproductive responses to temperature changes for aphids and corn borers. The results showed that the optimum temperatures for these species are being moved northward so that these pests will be able to thrive in regions that were previously unsuitable for them.
As the climate continues to warm, populations of crop pests will be expected to expand their ranges to more northern and higher altitude areas, increasing the risk of damage to global crops. Moreover, the occurrence of hotter and drier climates will make it more difficult to manage insect pests by using conventional methods of pest control such as spraying and crop destruction.
In addition to influencing the overwintering range of pests, the effects of climate change on their resistance to common pesticides will also be significant. Because most resistant phenotypes are transient, they usually die off in cold winter temperatures or emigrate at the end of the growing season. As the climate changes, this effect is expected to increase in size and intensity.
Habitat
Since insects are ectotherms, they cannot regulate their internal body temperature and are therefore extremely sensitive to weather changes. Consequently, pest populations can be greatly increased by climate change, especially in the form of temperature rise.
Temperature affects several key insect characteristics, including growth rate and phenology. Increasing temperatures create conditions that make it easier for the insects to breed and grow. Moreover, warm temperatures help multivoltine pest species develop at a faster rate compared to univoltine ones. This can lead to a larger population size of pests and increase their damage potential.
Additionally, pests’ thermal development tolerance, which is measured by growing degree days (GDD), will also be affected by climate change. This parameter can be used to predict the number of generations that a particular insect species will be able to complete in a year. The higher the GDD, the more rapidly the insect will be able to mature.
A large part of the food we eat is grown by plants, which need pollination from insects to thrive. Hence, it is important to protect these insects from being overpopulated by pests. Unfortunately, climate change is disrupting this delicate balance and is jeopardizing the ecosystem services that these insects provide.
Changing habitat is also expected to have a significant impact on the distribution and population dynamics of pests and their natural enemies, which are important for crop protection. The interactions between these organisms play a critical role in the ecological system, and any disturbance can be catastrophic for biodiversity.
As climate change continues, it is expected to exacerbate the geographic ranges of both pests and their natural enemies, which will affect agricultural production. It is important to monitor the expansion of these geographic ranges to identify new areas where they can pose a threat.
Even though global warming makes it harder for crop parasites to survive in their natural environment, they will continue expanding their ranges as long as there are suitable host plants available. Recent outbreaks of crop diseases such as the fall armyworm and the desert locust in Africa have been caused by heavy rains that created the perfect conditions for these pests to thrive.