The negative effects of higher temperatures, along with higher incidences of extreme events such as droughts and flooding, on staple crops are widely accepted but globing warming is bringing with it another dangerous threat: an over-abundance of crop-munching insects. A new model published on 31 August in Science has predicted that pest activity in crop-growing regions will continue to increase as average temperatures rise, resulting in significant losses in global crop yields (1).

According to the authors of the study, crop loss due to insects is rarely considered in models analysing the agricultural impact of global warming. However, warmer temperatures offer the perfect breeding ground for pests such as grasshoppers and caterpillars, and as a consequence, this growing number of insects will threaten global food security. In addition to the existing 5 to 20% of worldwide losses in major grain crops ― rice, corn, and wheat ― that pests already are already chomping away at, the model has shown that this will be boosted by another 10 to 25% per degree Celsius of warming.

The study was conducted by a team of researchers at the University of Washington. To project the future impact of insects on global and regional crop production, Prof Curtis Deutsch and his colleagues built on existing climate models by adding physiological data on hundreds of species of insects ― well-established relationships between temperature and the physiology and demography of insects. Based on the data, the impact of insects is expected to be driven by two factors: rising temperatures will increase the appetites of individual insects leading to increased food consumption; growth of the insect population, on the whole, will be accelerated.

The planet is expected to warm by an average of 2°C by 2100, if not sooner, and according to the model, if that happens wheat crops will shrink by 46%, rice by 19%, and maize by 31%. The regions hit worst will be those with temperate climates, such as the “corn belt” in the US, wheat fields in France, and the rice paddies of China. In contrast, insects in tropical environments may begin to die off after too much warming; therefore, rice yields may start to stabilize after a 3°C increase in temperature since it is mainly grown in tropical regions.

While the model predicts the dire effects of global warming and the influence that a resulting increase in insect numbers will have on global food supplies, other factors may limit these effects. Nonetheless, this study, along with previously established and generally accepted climate models, highlights the potential impact climate change will likely have on the yields of staple crops worldwide.

Corn, rice, and wheat provide food to approximately half the world’s population. Those most likely to be affected by crop loss due to climate change are communities living in poorer regions, therefore, as Deutsch suggests, planning for all the potential effects of climate change will be necessary.

(1) Deutsch, C. A. et al. Insect metabolic and population growth rates predict increasing crop losses in a warming climate. Science (2018). DOI: 10.1126/science.aat3466

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