Pests are major causes of crop yield losses. According to the U.N. Food and Agriculture Organization (FAO), between 20 and 40 percent of global crop yields are reduced each year due to damage caused by plant pests (insects and diseases).
Climate change is exacerbating food insecurity, and its negative impacts will worsen over time. This is happening via several pathways, among which plant pests are a leading cause. In fact, there are many possible pathways through which climate change may impact plant pests, including ecology, spatial distribution, and food chains.
Climate change may induce higher metabolic, developmental, survival, and reproductive rates in plant pests. For example, the main effect of temperature in temperate regions may be seen in winter survival. Non-diapausing, frost-sensitive species and those that are able to overwinter in their active stages, such as the aphid Myzus persicae, show increased winter survival in warm winters.
Climate change will have a significant bearing on the behavior of insects, as insects are cold-blooded organisms and are particularly sensitive to temperature changes. Through direct effects on the life cycle of insects, climate change will impact the distribution and severity of infestations of crops, in addition to indirect climatic effects on hosts, natural enemies, competitors, and insect pathogens. On average, pests have shifted polewards 2.7 kilometers (± 0.8 kilometers) per year since 1960, based on observations of hundreds of insects and pathogens. As a result, climate change may alter pest status fostering the appearance of invasive species.
Host plant tolerance or resistance to pests may decrease because of climate change. Relationships between insect pests and their natural enemies will change, resulting in both increases and decreases in the status of individual pest species. As a combined result of these effects, the annual grain harvest loss due to insects and diseases increased from 6.6 tons in the early 1970s to 14 tons in the mid-2000s, accounting for 2.7-percent loss of total grain harvest. In addition, it has been projected that global yield losses of major staple crops—such as wheat, rice, and maize—due to insects and diseases will increase by 10 to 25 percent for each degree of global mean surface warming.
Climate change has given rise to difficulties in pest monitoring and prediction, due to its alteration of pest behavior and population dynamics. Predicting the direct effects of climate change on pests has been further complicated by the interacting influences of increasing atmospheric carbon dioxide concentrations, changing climatic regimes, and altered frequency and intensity of extreme weather events. Projections have also been challenged by the fact that climate change can exert its effects on pests indirectly. For example, the differing responses of host crops and pest natural enemies, as well as changes in the efficacy of pest control strategies (biological control, synthetic pesticides, etc.), also affect pest responses.
The effectiveness of traditional pest control techniques will also be challenged. There will be a decrease in host plant resistance, an increase in the pesticide resistance of pests, and a lack of synchronization in the prey-predation system. A vivid example is rice, the major staple crop for approximately half the world’s population, and one of its major pests, brown planthopper (Nilaparvata lugens).
Enhancing farmers’ knowledge and skills to respond to climate change is key. Farmers must validate new technologies and approaches adapted to climate change, including digital-based technologies, and must integrate agro-ecological approaches. Farmer Field Schools (FFS) and other participatory approaches to improve integrated pest management (IPM) and sustainable production are proven methodologies to support farmers in this respect.
IPM remains the most integrated way to address the increasing severity of pests resulting from climate change. IPM is defined by the U.N. Food and Agriculture Organization (FAO) as “the careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and reduce or minimize risks to human health and the environment.”
IPM builds on understanding the ecology and biology of pests and their natural enemies, and enhancing the ecosystem services of agro-ecosystems. IPM principles include growing healthy crops, regular observations of all elements in the field, enhancing and conserving biological control, and ensuring that farmers have the knowledge and skills required to make informed decisions on pest and crop management.
FAO promotes IPM to best manage pests and diseases of crops. Farmers who are knowledgeable on IPM are able to make decisions reflecting the local context from an ecological and socio-economic perspective, rather than simply following a prescribed set of recommendations. IPM is responsive to changing conditions, including those caused by climate change, and remains the most appropriate way to manage pests.
FAO considers several specific integrated measures to address pests within the climate change context: establishing and strengthening the monitoring of the impact of climate change on pests and natural enemies; collecting data and setting up an initial database of climate change events and pests containing historical data and first-hand data from the monitoring system; building theoretical and empirical models to establish and explain evidence; and communicating these models through GIS visualization. In addition to using the existing FFS platform, knowledge exchange through a global (FAO) IPM platform to gather information on climate change is crucial to supporting farmers and policymakers in their efforts to better adapt to climate change.
Due to the transboundary nature of many pests, a global management approach is required in order for risk assessment and monitoring to be effective. A global information sharing system among regions, including information on diseases, insects, invasive alien species, and ecological conditions comprising weather data, is needed. For this reason, it is necessary to increase cooperation among countries and regions including national, regional, and global organizations.
At the global level, FAO manages transboundary plant pests within the framework of the Food Chain Crisis – Emergency Prevention System (FCC-EMPRES). The main strategy of FAO to address transboundary pests is to enhance prevention. This involves strengthening monitoring, early warning, early reaction, coordination, communication, and capacity development. For example, the FAO Desert Locust Information Service (DLIS) has been operating an early warning system to monitor weather, ecological conditions, and locust infestations on a daily basis since 1978. The DLIS is the global focal point and clearinghouse for all locust and locust-related survey and control data, which are analyzed to produce monthly bulletins, six-week forecasts, alerts, and warnings.
Controlling pest outbreaks exacerbated by climate change is crucial to increase food production and achieve U.N. Sustainable Development Goal (SDG) 2 on ending hunger, achieving food security, improving nutrition, and promoting sustainable agriculture, as well as SDG 13 on taking urgent actions to combat climate change and its impacts.