5 months, 3 weeks ago



Farmers in the Ethiopian Rift Valley are also watching the northern sky as Chinese talk about the flying bats in the sky changed because of the new coronavirus. 




A year and a half ago, typhoon mekunu (May 18) and Luban (October 18) accidentally attacked the desert areas on both sides of the Red Sea. By the beginning of January of the next year, the prelude of locust disaster had already appeared in the plains of Eritrea and Sudan. At the end of the month, one swarm of locusts crossed the 300 kilometer wide red sea, while the other moved slowly toward Egypt. Although under the control of the food and Agriculture Organization of the United Nations (FAO), the surrounding countries took some measures to kill the locusts, but the abnormal rainfall at the end of the 19th year made these efforts go to the East. Up to now, at least three locust disasters have continued to scour the horn of Africa, the border between India and Pakistan, southern Iran, and both sides of the Red Sea, especially the horn of Africa. 

The locust swarms here are extremely destructive. The locust swarms with a scale of one square kilometer can eat 35000 people's rations in a day. The food supply of 11.9 million people in this area is directly threatened by the locust disaster. According to the FAO's February 9 report, locust swarms have crossed the border between Uganda and Tanzania, while sporadic swarms have also been observed in the west side of the Sahel region. What's more pessimistic is that the locust population that has entered the incubation period has become increasingly fierce. According to the judgment of FAO, the expansion trend of locust disaster may continue until June this year, when the scale of locust population can even increase to 500 times of the present. 









Sahel: a general term for the long and narrow area between the Sahara desert in North Africa and the steppe area in central Sudan. Historically, it is known for frequent locust disasters
No matter in the Sahel or in the deserts of the Middle East, locusts are not rare. But the most imaginative observer will not associate them with the locust disaster that covers the sky and blocks out the sun. The local locusts are timid and dull. Without the protection of star light, they prefer to lurk among plants with monotonous protection Still, these 
 locusts prefer to live alone 
 and even shy away when their 
 peers are close to them, which is obviously different from those 
 yellow black (mature) or pink (immature) 
 death gods who are in the 
 hot sun 
 crazy group 
. 





 Where did the locust disaster come from and how will it be eliminated? 


Before Boris petrovitch Uvarov got to the bottom of the puzzle, these two complex problems of biology and environmental science had no way to solve. 

In 1920, yuvalov, whose family moved from Tbilisi to London, was finally able to get rid of the difficulties of life and focus on the two distinct locusts in the Middle East. He was keen to find that although there were great differences in appearance and habits, they seemed to be the same species from an anatomical point of view. He named them as 
 
 Schistocerca gregaria 
 - desert locust 
. However, why do desert locusts, which are solitary in nature, emerge in the daytime and in the night, and show the side of gathering and harming the world? According to yuvalov, climate may be the key to the transformation of desert locusts. 

Yuvalov, the father of locusts, found a way to find solutions, but it will be 80 years before he can solve the mystery. 

In 2005, Stephen Simpson of Oxford University began to search for the key that yuvalov had not found. He found that for most of the time, the harsh desert environment can only maintain rare and scattered vegetation, and desert locusts adapted to this habitat naturally tend to live in a scattered way. However, when the desert receives abnormal rainfall, the dormant plants suddenly grow, and the locusts living in this way also multiply in large numbers. But drought is the main role of the desert. The short-lived prosperity of the desert cannot last long. The ever shrinking food forces a large number of locusts to gather on the shrinking remaining vegetation. 
Knowledge points: 
 in the Central Plains of China, which is also plagued by locusts, such locusts gather more directly - the original stable vegetation will be reduced only after a drought, and the original stable locusts will inevitably get closer in order to pursue the decreasing vegetation. Many observers in ancient China have noticed some connection between locusts and drought, but under the simple thought of "the unity of man and nature", Chinese people often fall into the pattern of "the reaction of man and nature" when facing the locust disaster which is one of the "flood and drought locusts". The rulers believed that the locust disaster was the punishment of heaven for their own fault, but the official worship was lost After the effect, there are many kinds of folk sacrifices. After the worship of bawax temple, the God of expelling harm, the temple of insect king was built directly, and the temple of insect king could not come true. After that, Liu Meng, who is said to be able to expel locusts, turned to worship. In the Yellow River area where locust disaster is rampant, there are three temples at one time. 


 obviously, less and less vegetation can not maintain such a large population survival, migration has become the key to determine the survival of the population. But the long migration is obviously not what these solitary and weak locusts can cope with. They must form a large and close enough group, so that they can maintain the scale of population reproduction after the huge loss of long-distance flight. 

Isolated locusts need a change of habit, and the secret to change lies in their thighs. In the upper segment of locust's hind foot, there are many nerve receivers receiving mechanical stimulation. When more and more locusts inevitably rub their shoulders one after another, the collision of legs turns on this dangerous switch, 
 the nerve impulse makes the desert locust release acetonitrile, and the smell of the assembly signal floats in the air 
. 

 
 knowledge points: 
 the aggregation pheromones of various locusts are not the same. Acetonitrile plays a key role in the desert locust, the protagonist of this African locust disaster, but in the common Asian locusts in China, it is mainly cyclohexanol, 2,5-dimethylpyrazine, nonaldehyde, benzyl alcohol, (2,6,6-trimethyl-1,4-cyclohexanedione, etc. 

Now, locusts are no longer an individual with a weight of only 2.5G. Their group is the most surging force in the world. In 1875, the Rockies locust plague in the south of Missouri, North America, spread to 510000 square kilometers. Where 12.5 trillion locusts went, it was enough to make everything green. Although their flight ability is not excellent, the combination of locust swarms and wind can expand the expedition to a breathtaking level - crossing the Red Sea is not worth mentioning for them. In 1954, the locust swarms in northwest Africa spread all the way to Britain. In 1988, the locust swarms in Sahel crossed the Atlantic in only five days, unexpectedly appearing in 5600 Over the Caribbean islands, kilometers away, before the popularity of jet airplanes, the pilots of propeller airliners often met with swarms of locusts at an altitude of 3km. 




There is no doubt that the progress of technology has given us more means to fight against locust disaster, and China's locust eradication achievements are an excellent example. After a large number of chemical pesticides were used, the plague of locusts in the Central Plains finally disappeared in the 1960s. In 1986, China introduced locust microspore from the United States 
 Nosema (paranosema) locustae 
. This eukaryotic pathogenic microorganism can not only directly kill locusts, but also greatly reduce the fecundity of locusts, resulting in sublethal effects that limit the number of locusts and the ability to cluster. Similar locust viruses, pathogenic nematodes and more virulent fungi produced by transgenic technology can also play a similar role. 

However, it is a paradox that with the increasing means of confrontation, there is a trend of frequent Locust Outbreaks. Even in China, where most people have forgotten about locust disaster, locust disaster still exists. The desert locusts in Africa and the Middle East will hardly affect China due to the barrier of the plateau. However, in the western regions of China, such as Inner Mongolia, Xinjiang, Tibet, Sichuan and Gansu, the scale and frequency of grassland locust disasters have been increasing since the 1990s - 
 according to incomplete statistics, the annual average area of grassland locust disasters in China is 10 million hectares, and the loss of fresh grass per hectare is 600 kg 
. 

Such high-intensity use of pesticides and locust killing microorganisms can not completely kill the locust disaster in China. In Africa, the Middle East, Australia and other places where the technical means are more backward and human investment is more scarce, the locust disaster momentum is even more irremediable. 





 we may have to admit that locusts are the best standard to test the ecological stability of a place. Spraying pesticides and pathogenic microorganisms in the air can reduce the power of locust bomb to a certain extent, but a more active response should be to extinguish the detonating fuse. 

Looking back on the mechanism of locust disaster, it is not difficult to find that the locust disaster in ancient China was rampant, often accompanied by large-scale deforestation and cultivated land reclamation, the same story was repeated in the Sahel region, resulting in the imbalance of water resources and loss of ecological diversity, which made the locust disaster lost the last line of defense. In today's East African locust disaster, we should find the answer from the increasingly warming Indian Ocean. The abnormal rainfall in the past two years is just the tip of the iceberg in the context of global warming. Just as the impulse to pursue interests suppresses rationality, a series of chain reactions eventually urge the aggregation of pheromones to surge in locusts. 

A hundred years ago, yuvalov was looking for the beginning of the story, and today we are looking forward to the end of the story. 

Where is the road to the end? 

Locusts in the horn of Africa wait for the wind, not

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