Insect invasions link to warming
HUGE IMPACT: CROP LOSSES LIKELY TO ESCALATE
Yields for maize, rice and wheat down between 10-25% for each degree rise.
Several African countries are dealing with devastating outbreaks of desert locusts. This follows recent fall armyworm invasions, which affected more than 44 African countries. Countries also grapple with more localised pest invasions of insects like the South American tomato moth and maize stem borers.
The insects can consume, or destroy, huge amounts of crops. Just five invasive insect pests cost the African continent $1.1 billion (R16 billion) every year. Insect-pest related crop losses and pest invasions are projected to increase as the climate changes.
Projected changes include many regions becoming warmer, and insects thrive in warmth. Studies show insect-pest related yield losses for maize, rice and wheat are likely to increase between 10% and 25% for each degree Celsius of warming. These crops are the three most important in the world, accounting for 42% of calories eaten.
Broadly, there are two explanations for the rise in insect invasions: because the changing weather modifies insect traits and because it has an impact on their food, natural enemies and predators.
As temperatures rise, insects’ metabolism speeds up. As they burn more energy, they consume more, develop faster and larger, reproduce faster and lay more eggs. The result is an increase in populations, and more crop damage.
A changing climate will also affect rainfall patterns which affects the interactions between insect pests, plants and their natural enemies. Evidence shows drought increases the number of crop plant eating insects.
There is compelling evidence that insect distributional ranges are changing. As warming happens, insects are moving into new territories and habitats. Extreme conditions also alter plants’ nutritional value. Faced with a less nutritious plant, insects consume more.
Climate change may also alter the interaction of insect pests and their enemies. The ability of natural enemies to find the insect pests depends on their ability to tolerate changing weather conditions and how well they can move.
More research needs to be done to develop a clear understanding of how climate change directly and indirectly affects insects, to help us predict what invasions could happen and where.
Esther Ndumi Ngumbi is assistant professor, department of entomology, University of Illinois at Urbana-Champaign
Republished from
The Conversation