The Intergovernmental Panel on Climate Change (IPCC) – the UN agency on climate change – has released a new report highlighting the latest research on how the earth is changing and what those changes will mean for the future.
The report shows that carbon dioxide (CO2) levels and temperatures have increased dramatically, stating that the earth is likely to hit the critical warming limit of 1.5 ° C in the early 2030s. There are also dramatic changes in precipitation – water released from clouds such as rain, snow, or hail.
As an entomologist, I study insects and how climate change stressors – such as floods and droughts – affect insects’ feeding. I am also a food security advocate.
The projections in the report made me reflect on the many direct and indirect effects a warmer, more humid world will have on insects, their natural enemies, plants, and African food security.
Read more: How Changes in Weather Patterns Could Lead to More Insect Invasions
Across the African continent, the past few years have brought out some of these extremes and shown what a serious problem this is.
In southern Africa, for example, the autumn army worm outbreak continued to spread in 2016 due to increased rainfall and elevated temperatures – perfect conditions for reproduction and rapid growth. These conditions also supported the growth of over 70 host plants that are fed by the autumn army worm.
There is also a major desert locust outbreak in East Africa that began in 2019. It spread due to unusually heavy rainfall, which created the perfect environment for locusts to reproduce and increase in number and size. The rain also supports the growth of vegetation to feed them.
Here I outline some of the key findings of the report and how changes could affect insects and, indirectly, us.
Elevated levels of carbon dioxide
Global CO₂ levels are already high and are expected to continue to rise. An increase in CO₂ does not have a direct effect on insects, but it can change the nutrient quality and the chemistry of the plants. This indirectly affects insect herbivores.
According to recent research, for example, increased CO₂ reduces the nutrient quality of plant tissues by reducing the protein concentrations and certain amino acids in the leaves. To make up for this, insect herbivores eat more.
Increased CO₂ levels can also affect the development of insects and reduce their numbers – as shown in this study on dung beetles.
The report says global warming of 1.5 ° C and 2 ° C in the 21st
The temperature regulates the physiology and metabolism of the insects. An increase in temperature increases the physiological activity and thus the metabolic rate. Insects need to eat more to survive, and herbivores insectivores are expected to eat more and grow faster.
This will lead to an increase in the rate of population growth of certain insects. Because they grow quickly, they reproduce more. Their numbers will multiply and this will ultimately lead to more crop damage.
Read more: What temperature fluctuations mean for Africa’s tsetse fly
Previous research has predicted that for every one degree increase in global warming, insect crop losses will increase from 10% to 25%.
Drought and floods
It is expected that precipitation patterns – such as precipitation – will change as a result of climate change. The report assumes increased and frequent droughts and floods around the world. These environmental stressors affect plant productivity, plant chemistry, immune systems, nutritional quality, palatability and digestibility.
As a result, insects eat more plants and this can lead to more crop damage.
On the other hand, increased precipitation can support fresh vegetation (food for insects) and facilitate the build-up of insect populations. As with the desert locust, the persistent rain allowed them to ingest food, reproduce and spread. This was also the case with the army worm in autumn; Abundant rainfall supported the growth of their host plants. When food is no longer a limiting factor for the insects, their populations will continue to build.
Read more: A new model shows where desert locusts will breed next in East Africa
Decrease the effectiveness of natural enemies
All insects have natural predators or predators. For example, the corn stalk borer – a major pest of corn across Africa – has several natural predators such as Cotesia flavipes. These predators reduce insect populations and further reduce the need to use pesticides to control insect pests.
Predators can be affected by climate change in a variety of ways. For example, they can be sensitive to increases in temperature and precipitation, which ultimately reduces their numbers. Fewer natural enemies could lead to more pests. A study modeling temperature changes on stem bores in East Africa showed an increase in their number and a decrease in the influence of natural predators.
In addition, due to climate change, both the range of the plants and the insects will shift. In search of suitable conditions, insects move to new areas lacking their natural predators. This will cause their populations to grow, causing more crop damage.
More tasty food
Due to climate change, weather extremes are likely to occur together.
Research has shown that plants exposed to double stress can become even more palatable to insects. This is because when two stressors (e.g. drought and insectivore, flood and insectivore, or increased carbon dioxide and increased heat) coexist, their effects on plants can be additive or synergistic. This would lead to increased crop damage and decreased crop yields.
What can be done
Climate change will affect agricultural crops and their associated insects. These effects are complex, but it is certain that pest pressures will increase. There is a need for more insect monitoring and prediction and modeling so that we can develop strategies for adaptation.
In addition, countries should continue to monitor, share information, and use historical data and models to predict an uncertain future and prepare for the anticipation of hungry insect pests, with implications for crop productivity and food security.
Esther Ndumi Ngumbi is a Senior Food Security Fellow at the Aspen Institute New Voices.
By Esther Ndumi Ngumbi, Assistant Professor, Institute of Entomology; African American Studies, University of Illinois at Urbana-Champaign