Desert locusts: the history and the havoc

As billions of insects invade the Middle East and Africa, it is worth asking where they came from and if we can ever get rid of them for good

Generations have passed since East Africans have seen a plague of desert locusts comparable to the one that has been ravaging their crops over the last month. One of the swarms – there are several – is said to be the size of Moscow, consuming its own weight in crops every day. The Food and Agriculture Organisation, a UN agency, estimates the number of insects invading Kenya alone to be around 200 billion, covering an area of 2,400 square kilometres. Their origin remains the subject of much perplexity for local authorities – they hatched in Yemen, or maybe Oman, or perhaps even the Indian subcontinent.

Driven by insatiable hunger and the force of the wind, the swarm has taken to the west and to the east. Authorities in Somalia and Pakistan have declared states of emergency. Iran, which is already battling a coronavirus epidemic, has been afflicted, too. The insects have flown through Saudi Arabian deserts and reached pockets of the UAE.

Beleaguered FAO officials have warned that, if unchecked, the locust population could be 500 times greater by June. That would be a figure more easily expressed through the use of exponents.

It is difficult to overstate the scale of calamity that such a multitude of pests would bring upon the economies of the countries facing it. Farmers in India, Pakistan, Iran, Somalia, Ethiopia, Eritrea, Kenya, Uganda and Sudan face a nerve-wracking season.

But to better understand the desert locust, it is worth, for a moment, removing humankind from the equation. In fact, there is a name for a locust that does not affect our lives by joining a swarm and making short work of our crops. It is called a grasshopper.

In the biologist’s art of taxonomy, there is no nominal distinction between the grasshopper and the locust. A grasshopper becomes a locust when it swarms. (You could even say that the phrase “a swarm of locusts” is redundant.) It is one of the few species of animal that we assign a different name on the basis of its behaviour (and its impact on us), rather than the position it occupies on the evolutionary tree. There are 12,000 species of grasshopper. Twenty of them are capable of expressing the behaviour that turns them into locusts. They do not sit on a different branch from their cousins – perhaps just a different twig.

The cause of the behavioural change is simply population density. Studies on Schistocerca gregaria – as the desert locust is known to science – show that when members of the species come into close physical contact with one another, their bodies overload with serotonin (the same neurotransmitter responsible for feelings like euphoria in humans), and they become stronger, more aggressive and more social. In science-speak, they become more “gregarious” – hence the species name “gregaria”. Gregariousness is the emotion that promises the swarm.

The desert locust plague is a spasmodic horror. Last year, it travelled from Egypt across the Red Sea into Saudi Arabia and the western UAE, and in the early 2000s, it devoured many of the date palms in the southern Emirati city of Al Ain. Recorded incidences of the desert locust plague stretch back to pharaonic Egypt. It has been a harbinger of sorrow for the nations of the Middle East and North Africa for as long as they have been nations.

Like most insects, Schistocerca gregaria predates us by millions of years. In all those millennia, the locust co-existed with other animals without causing any harm because, of course, we were the first animal to farm. Ten thousand years ago, when humans pulled their first crops from the ground, we turned the humble grasshopper into the dreaded locust. What was previously just a normal part of the ecosystem became a plague, because we had something to lose.

Although the locust frequently demolished their harvests, ancient Egyptians only ever depicted it in their paintings in its singular, grasshopper form – never the swarm. Some scholars speculate that this is because they were too terrified to depict such a bad omen. The locust is in some ways the grasshopper plus fear. It is a state of mind.

The American entomologist Jeffrey Lockwood famously (in entomology circles) refers to the locust as not a species but a “process”. He also points out that if the body size of a grasshopper was scaled up to that of a human being, in its gregarious, locust state it would travel a distance of nearly 60,000 kilometres, farther than our civilisation-expanding ancestors travelled when circumnavigating the globe and conquering all of the land in between.

In the Middle East, we are proud of the region’s role in inventing agricultural civilisation. We, too, began gathering as a great collective, consuming and transforming the world around us. How poignant that nature should project that behaviour back at us, reminding us of the price.

Perhaps we can overcome the locust, and permanently evade this tax from nature. But as generations of agriculture officials can attest, that is a daunting task with several obstacles. For one, chemical fumigation of their nests is likely to have even more devastating effects on the wider ecosystem. For another, finding these nests is notoriously difficult. They are often in remote, hard-to-reach places.

In the Middle East and North Africa, the locust’s natural range is more than 29 million square kilometres, and the region lacks the infrastructure and political cooperation necessary to mount a coordinated response.

These obstacles, too, are very old in this part of the world. The first recorded locust control campaign occurred in the year 710BC, under the reign of King Sargon II in modern-day Iraq. In a series of letters, he notes that the only way to deal with the locust problem is for his governors to cooperate across their regional borders. The FAO, in a 2017 report commemorating 50 years of its anti-desert locust operations, references the letters, implying that the organisation is merely our modern torchbearer in this millennia-old struggle between man and nature.

Then there is the question of whether or not we should seek to exterminate the locust entirely. Perhaps we should. The Rocky Mountain locust, a North American species that in 1875 created a swarm almost 3,000km long and less than 200km wide, went extinct in the early 20th century in circumstances that remain mysterious to many entomologists. Or perhaps, some speculate, the loss of its nesting grounds through the expansion of American settlements simply subdued it to its passive, grasshopper state.

In any case, the loss of the species does not appear to have caused any major knock-on effects in the wider ecosystem.

One of the great benefits of civilisation, however, is that we can summon the ingenuity to find another way forward. There is hope among some researchers for developing a chemical that could inhibit serotonin production in grasshoppers, effectively drugging the species into submission.

The FAO has called for $138 million in emergency funds to help tackle the problem. It seems a very achievable figure, if we can summon the necessary spirit of cooperation. There are reports that we might, in fact, be the ones exacerbating the effects of the plague; climate change might be making the locusts’ numbers greater. Many of us are waking up to the fact that, in civilising ourselves and multiplying our numbers, human beings might not have been the great custodians of the planet we once told ourselves we were. Perhaps our own species has become a little too gregarious.

Sulaiman Hakemy is deputy comment editor at The National