The destruction of food supplies by crop pests is being exacerbated by the climate crisis, with losses expected to rise sharply, an analysis says.
Researchers say the world has been lucky to have so far avoided a major shock and has been living on borrowed time, and measures needed to be taken to diversify crops and encourage natural pest predators.
Losses to pests of the world's key crops, wheat, rice and corn, are expected to increase by about 46%, 19% and 31% respectively when global warming reaches 2°C, scientists say.
Global warming allows insects such as aphids, leafhoppers, stem borers, caterpillars and locusts to thrive. Increased warmth allows pests to develop faster, produce more generations each year, and attack crops longer as winters become shorter. Increasing temperatures also help pests invade places further from the equator and at higher elevations where it was previously too cold.
As a result, climate change-driven pest proliferation will be strongest in temperate regions such as Europe and the United States, according to the researchers. Temperatures may already have reached the limit for some insects in the tropics, they say, although clearing cropland into rainforests is introducing more pests.
Pest movement also accelerated by food exports along global trade networks. In parallel, destruction of natural habitats and intensive use of pesticides and fertilizers harm natural pest predators, while agricultural expansion creates new areas for pest infestation.
Pests and diseases destroy about 40% of global crop production, “posing a major challenge to global food security,” scientists said. The direct impact of the climate crisis on wheat, rice and corn is projected to reduce yields by 6-10% for every 1 degree of global warming.
“The world is focused on these staple crops – wheat, rice, corn, soy – and it's a very simplified and vulnerable system,” said Professor Dan Bebber from the University of Exeter, UK. Monocultures—large areas of one crop variety—can be destroyed by a single pest. “We've been lucky so far. But with the many threats of climate change and the many pests and diseases, we need to start thinking about a sustainable system that can feed everyone.”
“The Green Revolution, with simplification, plant breeding, massive use of fertilizers, fungicides and pesticides, saved millions of people from starvation,” he said. “But this was in a world where we weren't warming quickly, where pests and pathogens were just beginning their global journey, and where negative impacts on soils and biodiversity weren't coming back to bite us. We've been living on borrowed time, but we're heading toward a crisis and we need to do things differently.”
Analysis, published in Nature Reviews Earth & Environment Bebber and international colleagues, represents a conservative estimate of the increase in crop damage from pests due to the climate crisis because it focuses on insects and key crops and does not include microbial diseases, fungi and nematodes, and the full range of farmed foods.
Crop pests have evolved along with the plants they target, which provide high-quality food sources and can reproduce and spread quickly. They often develop resistance to pesticides.
Intensive use of fertilizers and irrigation in agriculture increases the quality and quantity of plants, meaning crop pests are much less affected by the destruction of their natural habitat. Many wild insect populations have plummeted.
The study said rising temperatures could have sudden effects, with small increases in temperature allowing the insects to produce new generations within the season. “When the Colorado potato beetle manages to go through another life cycle, it causes big problems,” Bebber said.
The climate crisis is causing heat levels to rise, but is also causing more rainfall in some places. The analysis found that they may flush out small pests, but wetter conditions generally benefit pests. Firstly, being small creatures, insects are at high risk of desiccation, and secondly, evaporation of rainwater cools the local environment, protecting it from the heat.
Scientists have said that environmentally friendly pest control can be achieved by restoring natural habitats to increase the number of parasitic wasps and other natural pest predators.
“Our increasingly simple agricultural systems are vulnerable, but supported by fungicides and pesticides, and that's fine as long as they work,” Bebber said. “But we have an evolution in pesticide resistance and we need to think seriously now about whether we want to use diversification as a strategy to help make our systems more resilient.”
Diversification may also include the intercropping of different crop varieties and the integration of crop and livestock production. Examples of the latter include traditional systems in Japan, where ducks eat snails and insects that attack rice, and in the UK, where sheep grazing winter wheat remove leaves affected by fungal diseases.
The analysis also suggests that artificial intelligence can improve crop protection by analyzing field and weather data to predict infestations and develop control strategies.
