HEAT IS ON THE HARDY LOCUSTS, BUT SWARMS WILL STILL CROP UP IN UAE
▶ Warming to curb numbers but insects will travel to devour crops, Daniel Bardsley reports
There are few more impressive sights in nature than a swarm of locusts. Billions of the insects, each capable of eating its own body weight in a day, devour almost all vegetation in their path.
While the swarms are fascinating, they are nothing short of terrifying to farmers – and agriculture in the UAE is not immune to their threats.
In early 2008, 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 crops falling victim to these voracious eaters.
Like many animals the desert locust is likely to be affected by climate change and a study has found that many parts of the Arabian Peninsula will probably become less hospitable for this creature, at least while it is in its more benign solitary phase.
It is when the desert locust is in its swarming phase that it can devastate crops.
Scientists based in France, Morocco and the US researched the possible distribution of the desert locust in 2050 and 2090. The findings were published in the journal Global Change Biology.
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 on more marked increases in temperature.
Detailed records of locust prevalence are kept by the UN’s Food and Agriculture Organisation, 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 a hardy creature. As the researchers note, 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 insect is likely to find life in some areas tougher going as the climate heats up.
The desert locust exists in northern and a southern groups, the latter of which are found in countries in southern Africa. Through climate change, this form is predicted to see its solitary distribution actually expand, but this is not the type that invades the UAE.
Plagues that have affected the Emirates have come from the northern group, which is found across vast areas 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 the more and less severe 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 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.
But unfortunately, this contraction in range does not necessarily translate into a reduced risk from swarms in this part of the world, mainly 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 devastate crops.
“During the gregarious phase, which is the one that causes significant agricultural damage, the individuals can travel great distances 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 lead author of the study, Dr Christine Meynard, of the French National Institute for Agricultural Research.
The study’s other authors – 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 a French agricultural research centre that co-operates 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 early warning system in place, co-ordinated by the UN agency and based on climatic information and historical data on distributions, to identify when and where outbreaks are likely. This allows preventive work to nip threats in the bud and prevent outbreaks spreading.
By the time outbreaks occur, the situation becomes much more difficult to control, hence the need for vigilance.
When an outbreak seems likely, the alert is raised by national centres and insecticide spraying is carried out. The earlier the alarm is raised, the better, because it reduces the amount of spraying needed, saving money and reducing any environmental damage.
If initial measures fail to prevent an outbreak, countries can seek help from the UN agency, which may be able to provide funding and resources to 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.
Researchers such as Dr Meynard are also trying to understand how the uncertainty in large-scale predictions of temperature and rainfall affects species distribution.
She is also looking at common life-history characteristics that have allowed certain animals to become agricultural pests.
All of these approaches should allow for better predictions about how desert locusts will respond to a changing climate.
But one thing seems clear. While Arabia will become a less hospitable place for the locust, the risks these creatures pose to agriculture in the UAE will not disappear soon.
During the gregarious phase – the one that causes significant damage – swarms can travel great distances DR CHRISTINE MEYNARD lead author of the study