Destruction of food supplies by crop pests is being exacerbated by the climate crisis, with losses expected to rise, an analysis has found.
The world is fortunate to have so far avoided a major shock and is living on borrowed time, with action needed to diversify crops and boost the pests’ natural predators, the researchers said.
The scientists said that the major global crops, namely wheat, rice and maize, are expected to see losses from pests increase by about 46%, 19% and 31%, respectively, when the global temperature rise reaches 2 degrees Celsius.
Global warming helps insects such as aphids, planthoppers, stem borers, caterpillars and locusts to thrive. Greater warmth enables pests to develop faster, produce more generations each year and attack crops for longer as winters shorten. Rising temperatures also help pests invade places far from the equator and on highlands that were previously very cold.
As a result, climate-induced pest blooms will be worse in temperate places, such as Europe and the United States, the researchers said. Temperatures may have already reached their limit for some insects in the tropics, although clearing of farmland into tropical forests supports more pests, they said.
The movement of pests through food exports across global trade networks is also accelerating. In parallel, the destruction of natural habitats and the intensive use of pesticides and fertilizers paralyze the pests’ natural predators, while the expansion of agricultural land creates new areas for crop pests to invade.
Scientists said pests and diseases destroy about 40% of global crop production, “creating a major challenge to global food security.” The direct impact of the climate crisis on wheat, rice and maize is expected to reduce yields by 6-10% for every 1°C of global warming.
Professor Dan Pepper, from the University of Exeter, UK, said: “The world is focusing on these key grains – wheat, rice, corn and soybeans – and it is an overly simplified and weak system.” Monocultures – large areas that grow one type of crop – can be wiped out by a single pest. “We’ve been lucky so far. But with the multiple threats of climate change and so many pests and diseases, we need to start thinking about a resilient system to feed everyone.”
“The Green Revolution, with simplification, plant breeding and extensive use of fertilisers, fungicides and pesticides, saved millions of people from hunger,” he said. “But this happened in a world where we were not seeing temperatures rise rapidly, where pests and pathogens were just beginning their global journey, and where negative impacts on soils and biodiversity were no longer hurting us. We were living on borrowed time but we are heading towards a tough time, and we have to do things differently.”
analysis, Published in Nature Reviews Earth & Environment This assessment, by Pepper and international colleagues, is a conservative assessment of the increasing damage caused by pests to crops due to the climate crisis, as it focused on insects and major cereal crops, and did not include microbial diseases, fungi, nematodes and the full range of foods that are grown.
Crop pests have evolved along with the plants they target, which provide high-quality food sources, and can reproduce and spread rapidly. They have often developed resistance to insecticides.
The use of fertilizers and irrigation in intensive agriculture enhances the quality and quantity of plants, meaning that crop pests are much less affected by the destruction of natural habitats that has led to declines in wild insect populations.
The analysis said that rising temperatures could cause sudden effects, as small increases in temperature allow insects to produce another generation within a single season. “When the Colorado potato beetle can go through another life cycle, it causes big problems,” Pepper said.
The climate crisis is increasing heat levels but is also causing heavy rain in some places. These can wash away small pests, but wet conditions generally benefit pests, the analysis said. Firstly, as small organisms, insects are at great risk of dehydration, and secondly, the evaporation of rainwater cools the local environment, protecting it from the heat.
Scientists said environmentally friendly pest protection could be achieved by restoring natural habitats to increase numbers of parasitic wasps and other natural pest predators.
“Our simpler agricultural systems are at risk, but they are maintained by fungicides and insecticides, which is fine as long as they work,” Pepper said. “But we have the evolution of insecticide resistance and we have to think carefully now about whether we want to use diversification as a strategy to help make our systems more resilient.”
Diversification can also include growing different types of crops together and combining crop and animal farming. Examples include traditional systems in Japan, where ducks eat snails and insects that attack rice, and in the United Kingdom where sheep grazing on winter wheat remove leaves affected by fungal diseases.
The analysis also stated that AI can enhance crop protection by analyzing field and weather data to predict infestations and develop strategies to address them.