There are few more impressive sights in nature than a swarm of locusts.
Numbering in the billions of individuals, each capable of consuming its own body weight in a day, these plagues can devour almost all the vegetation in their path.
While these swarms’ dramatic appearance makes them beloved of wildlife documentary makers, they are nothing short of terrifying to farmers. And agriculture in the UAE is not immune to their threats.
In early 2008, for example, it was reported that the country was experiencing its worst plague of locusts in 25 or even 50 years, with date palms in Al Ain among the crop plants falling victim to these voracious eaters.
Like many animals, the desert locust is likely to see its distribution affected by climate change, and a new study has found that many parts of the Arabian peninsula will probably become less hospitable for this creature, at least when it is in its more benign solitary phase.
It is when the desert locust is in its gregarious phase, referenced in the creature’s Latin name, Schistocerca gregaria, that it creates swarms that can devastate crops.
Carried out by scientists based in France, Morocco and the United States, and published in the journal Global Change Biology, the research looked at the potential distribution of the desert locust in 2050 and 2090. For each date, the researchers considered an optimistic scenario in which global temperature rises were more limited, and a more pessimistic outcome, which was based upon heavier temperature increases.
Detailed records of locust prevalence are kept by the United Nations’ Food and Agriculture Organisation (FAO), and the researchers combined this information with a complex climate model using 35 variables, among them temperature, rainfall and soil moisture, to forecast future distributions.
The desert locust is nothing if not a hardy creature. As the researchers note in their paper, it has “evolved in environments that are among the hottest, most arid and most variable … in the world”.
But despite its ability to cope with extreme conditions, the desert locust is likely to find life in some areas tougher going as the climate heats up.
The desert locust exists in a northern and a southern clade, the latter of which is found in several countries in southern Africa. Through climate change, this form is predicted to see its solitary distribution actually expand, but this is not this type that invades the UAE.
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Instead, plagues that have affected the Emirates have come from the northern clade, which is found across a vast swathe of central, eastern, western and northern Africa, plus the Arabian peninsula and as far east as India.
Under the more severe climate change forecast for 2050, and under both the more severe and the less scenarios for 2090, there will be significant contractions in this distribution. Much of the Arabian peninsula will be too extreme and the desert locust may no longer be present in its solitary phase in a large part of this area. Only the Red Sea coastlines of Saudi Arabia and Yemen are likely to remain as favourable to the creature as they are now.
Unfortunately, however, this contraction in range does not necessarily translate into a reduced risk from plagues in this part of the world, primarily because when the locusts turn to the gregarious phase and form plagues, they can travel thousands of miles. They may not be able to survive in the long term in these “invasion areas”, but they can still cause considerable harm to crops in them.
“During the gregarious phase, which is the one that causes significant agricultural damage, the individuals can travel great distances away from their long-term survival sites, and those outbreaks may affect much wider areas than those occupied during recession periods by the solitary phase,” said the first author of the study, Dr Christine Meynard, of INRA, the French National Institute for Agricultural Research.
The other authors of the study, Pierre-Emmanuel Gay, Dr Michel Lecoq, Antoine Foucart, Dr Cyril Piou and Dr Marie-Pierre Chapuis, all of whom are based in France or Morocco and work for the CIRAD, a French agricultural research centre that cooperates with developing nations, are part of a team aiming to improve the tools to predict the risk of desert locust outbreaks.
They note that, “of concern to the risk of invasion in the Arabian peninsula, the gregarisation areas in Yemen, Saudi Arabia and Sudan were shown to remain suitable for the desert locust under climate change”.
As a result, the authors said “vigilance should not be decreased” because some of the areas where outbreaks can start are in the Arabian peninsula and can affect the whole region.
There is a complex and detailed early warning system in place, co-ordinated by the FAO and based on climatic information and a wealth of historical data on distributions, to identify when and where outbreaks are likely. This allows preventative work to nip threats in the bud and prevent outbreaks spreading.
By the time outbreaks occur, the situation becomes much more difficult – and expensive – to control, hence the need for continued vigilance. When an outbreak seems likely, the alert is raised by national centres and insecticide spraying is carried out to try to prevent swarms. The earlier the alarm is raised, the better, because it reduces the amount of spraying needed, saving money and reducing any possible environmental damage. If initial measures fail to prevent an outbreak, countries can seek help from the FAO, which may be able to provide funding, expertise and resources to help contain the outbreak.
On a positive note, the scientific understanding of how these creatures grow, reproduce, form swarms and survive under changing temperatures is likely to improve thanks to laboratory analysis. Also, considering a wider environmental scale, researchers such as Dr Meynard are trying to understand how the uncertainty in large-scale predictions of temperature and rainfall affects species distribution. Dr Meynard is also looking at common life-history characteristics that have allowed certain animals to become agricultural pests, and is hoping to understand how this can predict risks under climate change.
All these various approaches should together allow for better predictions about how desert locusts will respond to a changing climate.
One thing seems clear for the moment, though. While Arabia will become a less hospitable place for the desert locust, the risks these creatures pose to agriculture in the UAE will not disappear soon.