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The ravenous swarm stretches as far as the eye can see.
肆虐的蝗虫成群结队，蔓延至天际。
It has no commanding general or strategic plan; its only goals are to eat, breed,
蝗群没有将帅，也无策略指导；它们的目标只有蚕食、繁衍，
and move on -- a relentless advance that transforms pastures and farms into barren wastelands.
然后继续向前--残酷无情的蝗虫过境之后，牧场、农场全都沦为不毛之地。
These are desert locusts -- infamous among their locust cousins for their massive swarms and capacity for destruction.
这是沙漠蝗虫--在蝗虫家族中臭名昭著，因为它们数量庞大且破坏力惊人。
But these insects aren't always so insatiable.
但这类昆虫并非总是如此贪得无厌。
In fact, most of the time desert locusts are no more dangerous than garden-variety grasshoppers.
事实是，大多数时间，沙漠蝗虫并不比花园中的蚱蜢们危险多少。
So what does it take to turn these harmless insects into a crop-consuming plague?
那么，是什么驱使这些无害的昆虫们酿成一场毁坏庄稼的蝗灾呢？
Desert locust eggs are laid in the damp depths of desert soil, in arid regions stretching from North Africa to South Asia.
在干燥的北非到南亚一带，沙漠蝗虫将卵产在潮湿的沙漠土壤深处。
During the dry weather typical in these ecosystems, desert locusts live a solitary lifestyle.
在这些生态系统中典型的干燥天气里，沙漠蝗虫过着孤独的生活。
Adolescent hoppers will spend a few lonely weeks foraging for plants, before growing wings, reproducing, and dying.
幼蝗虫会独自生活几周，孤单地寻觅植物，然后会长出翅膀，繁衍后代，最后死去。
But when a region receives an abundance of rain, the scene is set for a startling transformation.
但如果某个地区经历了一场充沛的降雨，这个场景则将迎来惊人的转变。
Increased moisture supports more vegetation for newly hatched hoppers to eat, leading large groups to feed in close proximity.
增长的水汽滋养了更多植被，新生的蝗虫有了更多的食物，导致大群蝗虫在邻近区域觅食。
The frequent contact stimulates their leg hairs, triggering the release of a hormone that causes them to actively cluster even closer.
频繁的接触刺激了它们腿毛的生长，引发一种激素的释放，这种激素会导致它们主动聚集地更加紧密。
Gluttonous crowds of locusts produce huge amounts of poop, which carries a pheromone that furthers their transformation.
贪吃的蝗虫们排出大量粪便，其中所含的一种信息素进一步促进它们的变化。
The hopper's diet shifts to include plants with toxic alkaloids.
幼蝗虫的饮食发生转变，它们开始吃含有有毒生物碱的植物。
Soon, the locusts take on a striking pattern that warns predators of their newly poisonous nature.
不久后，蝗虫的外表变得鲜艳这一变化，会警告捕食者们它们身上开始带有毒性。
Smaller groups merge into bands of millions, which mow down virtually all plant life in a kilometer-wide swath.
小蝗群融合成上百万只的大部队，像一把长达千米的镰刀，几乎将所经之处的植物收割殆尽。
Roughly every week they shed and expand their exoskeletons, growing to roughly 50 times their hatching weight in just one month.
它们几乎每周都会褪一次壳，其外骨骼将会变大，短短一个月时间，就能长到约出生时的50倍重。
Finally, the metamorphosis is complete. The adults beat their translucent wings and take flight as a full-fledged locust swarm.
最终，变形完成。成年蝗虫们扇动半透明的翅膀，随进化完全的蝗虫群一起飞去。
In this gregarious phase, these long-winged, brightly colored creatures
在这一群居阶段，这群长翅、色彩明亮的生物，
appear so different from their solitary counterparts that they were long thought to be a separate species.
与独居时期的蝗虫差异显著，以至于人们一直以为它们是两种物种。
A typical swarm contains more locusts than there are humans on the planet, covering hundreds of square kilometers in a dense cloud.
一个蝗群内的蝗虫数量一般比世界人口数量还多，面积可达上百平方公里，如乌云般遮天蔽日。
At these numbers, desert locusts easily overwhelm their predators.
数量如此巨大，沙漠蝗虫轻易便压制了其捕食者。
A large swarm can match the daily food intake of a city of millions,
一个大蝗群每日消耗的食物抵得上数百万人口的城市所需，
and flying with the wind, the insect invasion can travel up to 150 kilometers a day.
顺着风向，蝗群每日可飞行高达150公里。
This living tornado can also cross large bodies of water. In 1988, a swarm even managed to traverse the Atlantic Ocean.
这群活飓风还能飞越广阔的河流海洋。1988年，一个蝗群甚至成功横穿大西洋。
The locusts likely formed rafts to rest at night, before fueling up in the morning with a nourishing breakfast of their dead kin.
蝗虫们晚上大概会排成筏子一样来休息，早上它们会将亲属的尸体当作早餐，饱餐一顿补充能量。
While flying over land, they seek out moist soil to lay eggs.
飞越陆地时，他们会寻找潮湿的土壤产卵。
Swarming mothers transfer their gregarious condition to their offspring, making it likely that the next generation will form another swarm.
蝗群中的蝗虫妈妈们将群居的生活习惯传给后代，这样很可能它们的下一代又会组成下一个蝗群。
This means that while an individual desert locust lives only three months, a plague can last up to a decade.
这就意味着，尽管一只沙漠蝗虫的寿命只有三个月，一场蝗灾却可能持续十年。
The potential for a years-long plague isn't unique to desert locusts, but the region they inhabit makes the prospect particularly deadly.
并非只有沙漠蝗虫有酿成数年蝗灾的可能，但它们生活的地区，使得蝗灾的影响尤其致命。
Their habitat spans some of the world's poorest countries, largely populated by people who grow their own food.
它们生活的区域贯穿了若干世界上最贫困的国家，那里居住着大量种植庄稼自给自足的人。
By consuming crops and pastures, these insects directly endanger 10% of humanity.
通过啃食农作物和牧草，这些蝗虫直接导致全球10%的人口面临死亡风险。
Fortunately, a desert locust plague doesn't last forever.
幸运的是，沙漠蝗虫蝗灾并不会一直持续下去。
When a wet period ends, vegetation becomes scarce and egg laying conditions decline.
当雨季结束，植被减少，产卵条件恶化。
As existing swarms die off, new hatchlings spread out in search of food, creating enough distance to prevent solitary locusts from transforming.
随着现有的蝗群逐渐消亡，新生蝗虫四散开来寻找食物，创造出足够大的距离，阻止这些独居的蝗虫们变化习性。
Human intervention can also help.
人类干预也能起到作用。
Researchers use satellite imagery to identify regions at risk of becoming locust hotspots and alert local governments.
研究人员使用卫星影像来识别蝗灾风险区域，并向当地政府发出警告。
While most countries fight back with chemical insecticides,
在大多数国家使用化学杀虫剂对抗蝗灾时，
some regions have found success using fungal diseases that are lethal to locusts but safe for people and the environment.
一些地区使用能够杀死蝗虫的真菌病害成功地消灭了蝗灾，但其对人和环境无害。
Unfortunately, other modern practices are exacerbating the threat. Fields densely packed with a single crop are like a table set for locusts.
不幸地是，现代社会的一些做法加剧了蝗灾威胁。稠密地种植着单一作物的田野，就像给蝗虫摆放的餐桌。
And erratic weather caused by climate change makes swarms harder to predict.
气候变化导致的多变天气，也使蝗灾更难预测。
If we plan to discourage lonely locusts from becoming catastrophic crowds,
如果想要阻止散居的蝗虫演变成灾难性的蝗群，
humans need to cut carbon emissions, rethink our agriculture, and generally reconsider our own ravenous appetites.
人类需要减少碳排放，重新考虑农业布局，以及再反思一下我们自己贪婪的口腹之欲。
