Graze: the act of feeding on low-growing plants, like grasses.
Migration: movement of an animal or a group of animals from one place to another.
Nitrogen: a chemical that is important for all organisms to build tissues. Nitrogen makes up 78% of the Earth's atmosphere.
Protein: a type of molecule found in the cells of living things, made up of special building blocks called amino acids.
Swarm: a large, dense group; or to move somewhere in a large group.
Telecoupling: when places that are far apart are connected by an event or other occurrence.
The sky darkens with moving sheets pushing across the horizon. What looks like a cloud of dense dust is something entirely different: locusts. Your first thought is to avoid being hit by the flying grasshoppers. But then you realize they are also under your feet.
They are landing everywhere—on the ground, on your crops, and even on your stored food. That's when you realize your biggest problem. The locusts are eating everything.
Around the world, there are many people whose lives depend upon the food they grow on their own land. If locusts eat it all, then people either go hungry or are forced to buy expensive food. Usually a little of both.
Hunger and higher food costs can affect communities in many ways. They may have to spend money meant for school, or healthcare, or other things that a community needs. This is what happened in the West African village in Senegal, where senior sustainability scientist Arianne Cease first encountered locusts.
Locusts are a special kind of grasshopper that can form a swarm. These grasshoppers gather in groups and migrate when exposed to certain conditions, such as a crowded population.
A locust swarm might have almost 100 billion hungry insects in it. A swarm with that many bugs would be almost as big as the entire city of Los Angeles. And an adult locust can eat its weight in food in a single day. Could you eat your weight in food in a single day? No way. Locusts are really, really hungry insects.
And all that hunger can destroy all the plants or crops in an area. All those locusts could eat 423 million pounds of plants in one day. When all the food is gone, the locusts just fly or march along to the next place, leaving a wasteland behind them.
During an outbreak year, locusts could cover one-fifth of all the land on Earth. When that happens, one out of every 10 people on the planet suffers. That’s why Cease studies locusts – to find a way to help the people who have to deal with locust outbreaks.
Locust outbreaks have been happening for thousands of years. Locust swarms are even written about in the Bible. In all that time, people have not found out exactly what causes locusts to swarm and migrate. A crowded population is an important trigger, but there are other environmental factors involved that have yet to be uncovered.
Cease's research team focuses in part on some of the causes of locust migration. Grasshoppers usually like to be alone. So what makes them form hungry swarms and migrate from place to place?
Animals and plants, including insects, need protein to grow. And locust swarms often happen in places where the soil is low in nitrogen – a nutrient necessary to make proteins. In low nitrogen areas, plants can’t make as much protein. Low-protein plants are a favorite snack of locusts.
For some locust species, if they have only high-protein plants to eat, they actually grow more slowly and some even get sick or die. Locusts depend on low-protein food. Low-protein food is often found in areas where cattle or other livestock graze heavily…and even more so, where they graze too much. So overgrazing seems to be one potential cause of locust swarms.
When livestock animals eat too much grass from one place over a long time period, it makes the soil less healthy. Nitrogen washes away, and the grasses get low in protein.
That’s when locusts start to grow stronger, group together and form a swarm. But these locusts don't just affect the overgrazed communities. They migrate to nearby or distant locations, eating crops and food stores wherever they go.
Linking distant communities with such environmental effects is called telecoupling, and it's an important focus for Cease. If locust swarms are going to be lessened in the future, scientists must look at the problem broadly across the landscape and from many different angles.
They must take into account the actions of the farmers, ranchers, and community members, in addition to the biology of the locusts. And they must do this across different countries with separate governments. By getting many of these groups to work together, Cease is hoping to help prevent some of these swarms.
Using an approach like this, Cease and her colleagues just might turn locust management on its head. Working with people from China, Australia, Senegal, Canada, and the United states, they are tackling this worldwide issue so that one day, people won't have to lose so much to locusts.
Learn more about locust research at livingwithlocusts.com.
Additional images via Wikimedia Commons.
Karla Moeller, Michelle Schwartz. (2015, September 15). On the Lookout for Locusts. ASU - Ask A Biologist. Retrieved September 18, 2020 from https://askabiologist.asu.edu/fr/explore/lookout-locusts
Karla Moeller, Michelle Schwartz. "On the Lookout for Locusts". ASU - Ask A Biologist. 15 September, 2015. https://askabiologist.asu.edu/fr/explore/lookout-locusts
Karla Moeller, Michelle Schwartz. "On the Lookout for Locusts". ASU - Ask A Biologist. 15 Sep 2015. ASU - Ask A Biologist, Web. 18 Sep 2020. https://askabiologist.asu.edu/fr/explore/lookout-locusts