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How Climate change will increase locust outbreaks in Future?

How Climate change will Increase locust outbreaks in Future?

Climate change will dramatically increase the growth of locust swarms, according to a new study, making more crops vulnerable and threatening food security, according to a study by the research team at Arizona State University (ASU).

The study, recently published in Ecological Monographs, outlines the results of a considerable amount of data collected on the physiology of South American lobsters and demonstrates that species distribution models that consider physiology in addition to temperature can reshape what we can expect to see as climate change continues.

“A unique aspect of our study is that we combined many different research approaches, including field observations, laboratory experiments, and computational modelling,” said Jacob Youngblood, a recent biology Ph.D. graduate from ASU and the study’s first author.

Climate change will dramatically increase the growth of locust swarms. Photo credit: unsplash/Heiko Haller

“To combine these approaches, we brought together a diverse team of researchers, including physiologists, ecologists, entomologists, and farmers. Collaborating with such a diverse team allowed us to study the effects of climate change on multiple aspects of lobster biology.”

From Egypt of pharaohs

Since the days of the ancient Egyptian pharaohs in 3200 BC, locusts have been emerging in massive swarms that almost completely destroy crops and plants.

Why do these destructive swarms suddenly occur?

Like people, lobsters can be shy or outgoing. For the most part, lobster populations can spend several seasons in a low-density population, called the solitary phase. Locusts are a cryptic brown or green: shy, solitary, and relatively harmless on a global economic scale. ‘

However, when the circumstances are right, locust numbers swell to overcrowding, triggering a drastic shift to a gregarious phase: social, brightly coloured, and capable of forming migratory swarms of 80 million locusts per square kilometre.

Each locust eats up to 2 grams of vegetation per day; a large swarm can travel 90 miles in a day, removing the food equivalent of 35,000 people. No wonder they are considered the most destructive pests in the world.

To help unravel the reasons behind the swarms, the team studied the physiology of the South American locust (Schistocerca cancellata).

locust outbreaks. Photo credit: flickr/UNSOM

“Seeing thousands of locusts together really made me realize how big a locust problem can be for local farmers and land managers,” Youngblood said.

Most locust research has been done on colonies that have been reared in the lab over the years, so our research was a unique opportunity to study locusts propagating in their natural environment.

How locusts behave in future?

To try to predict where swarms will migrate and where crops will be threatened, scientists use species distribution models, and computer algorithms that predict the distribution of a species in a geographic area using environmental data.

The most common modelling technique has been the correlational model. However, due to the changing climate around the world, this method has lost its effect, considering the things that are unknowingly changing.

locust outbreaks. Photo credit: Sven Torfinn/unep

The research team created a modelling approach, collecting data on grasshopper physiology to inform their model. In this case, the researchers measured how quickly lobsters digest food in different environments.

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Professor Jon Harrison says that how organisms will respond to climate change, and to help humans survive and thrive despite climate change, will require an in-depth study of the complex inner workings of our fellow biological organisms.

Strength of locust swarm

Temperature is an important part of the environmental data traditionally used for connected models, which has a great impact on lobsters’ feeding habits.

However, these environmental data alone cannot fully predict the effects of climate change on locust populations. First, existing locusts can nibble on crops in different temperatures. As herbivores that can travel long distances in search of readily available food, lobsters can fill their stomachs faster than they need to.

While lobsters can and will eat in a wide range of temperatures, the optimum temperature for digestion is much more specific.

Youngblood and his associates focused on this element as a decisive criterion for a thriving locust population likely to result in outbreak scenarios.

The team measured how thermal conditions affected the feeding and digestion rates of field-caught lobsters and used this data to model energy gain under current and future climate scenarios. They then established this new data as a predictor variable for a new species distribution model that predicted the spread of locust outbreaks under multiple scenarios.

Their predictions show that locusts will be able to assimilate much more energy in future climates than in current climates, between 8% and 17% more energy per rainy season than today, proportional to how much warmer it is.

More chance of outbreaks

South American lobsters normally only complete two generations per growing season. This increase in energy due to the rainy season would cause a reduction in generation times and stimulate population growth, which would generate more swarms. The warmer climates of the future will allow populations to grow and develop faster, enduring more years with three generations per season and more chance of outbreaks.

Migratory populations of South American locusts are also expected to expand their range away from the equator due to climate change. Models that consider locust physiology actually predict a smaller expansion range than typical correlative models, but physiology-based models also predict an increase in population growth rate, resulting in damage to crops.

locust outbreaks and climate change. Photo credit: flickr/Bernard DUPONT

Previous models predicted that crop loss from insect pests would increase by 10-25% with climate change, but scientists did not know if these predictions were relevant to the South American locust. The new model created by Younglood matched previous models, predicting a 17% increase in crop losses to South American locusts.

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