Le Sahara n'a pas toujours été le désert de sable sans fin que nous connaissons aujourd'hui—il était autrefois luxuriant et verdoyant ! 🌿 Il y a environ 6 000 à 7 000 ans, il était couvert de prairies, de rivières, et même de lacs, abritant des animaux tels que des éléphants et des hippopotames. Les scientifiques affirment que ce changement s'est produit en raison de modifications de l'orbite terrestre, qui ont perturbé les pluies de mousson maintenant la région fertile. À mesure que les pluies se dirigeaient vers le sud, le Sahara s'est asséché, se transformant en le désert que nous voyons aujourd'hui. Mais ce qui est vraiment étonnant, c'est que ce cycle de verdissement et de désertification s'est produit plusieurs fois au cours de millions d'années. Qui sait—peut-être que le Sahara redeviendra vert un jour ! 🌎 Animation créée par Sympa.
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Musique par Epidemic Sound https://www.epidemicsound.com
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Nos réseaux sociaux :
Facebook: https://www.facebook.com/sympasympacom/
Instagram: https://www.instagram.com/sympa.officiel/
Stock de fichiers (photos, vidéos et autres):
https://www.depositphotos.com
https://www.shutterstock.com
https://www.eastnews.ru
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Si tu en veux encore plus, fais un tour ici:
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FunTranscript
00:00When you imagine an epic scene in the desert, with its crushing sun, its infinite dunes, and its almost supernatural oases,
00:08it is natural to imagine the mythical Sahara, isn't it?
00:11Yet, what would you say if you were told that 11,000 years ago, this vast sea of burning sand had a radically different appearance?
00:19Of course, no one was there to testify to this.
00:22But it is said that at that time, what we now call a desert, was a real Eden,
00:28dotted with lakes, rivers, green meadows, and even forests.
00:33So, where did all this water go?
00:36There are many stories about these ancient times when the deserts were covered with jungle and luxurious forests,
00:44until an upheaval, whether it be climate change or titanic earthquakes,
00:49transformed these fertile lands into arid dunes.
00:52But what would you think of a hypothesis, according to which the Sahara would have been transformed into a desert by human activities and... goats?
01:00Over the millennia, the Sahara has experienced alternations marked between wet and dry periods,
01:06mainly due to slight variations in the orbital inclination of the Earth,
01:11influencing the amount of solar radiation received by the atmosphere.
01:15There were even phases called African wet periods,
01:19where abundant rains metamorphosed this arid landscape into a screen of sparkling greenery.
01:25However, between 8 and 4,500 BC, an unusual phenomenon shook the region.
01:31Some areas went from a humid climate to an arid climate far too quickly for this to be explained only by orbital variations.
01:39In a relatively short period of time, the greening Sahara gave way to the desert we know today.
01:45If you ask scientists about the reason for this change, they will undoubtedly evoke a bad parameterization of the data.
01:53This jargon may seem nebulous, so allow us to translate,
01:57it means that they themselves are not sure and that they still lack several pieces of the puzzle.
02:03By analyzing old samples of soil and pollen, however, researchers have detected an intriguing tendency.
02:09Where shepherds, humans accompanied by their domestic animals, had to stay, the vegetation seemed to be changing.
02:17To believe that every time these men and their herds crossed green expanses,
02:22they left behind them only bushes and desert landscapes.
02:26What an irony!
02:28It seems that the overgrowing practiced by these populations has contributed to drying the atmosphere,
02:34because the plants, by releasing moisture, participate in the formation of clouds.
02:39This deforestation would have intensified the sun, thus precipitating the end of the humid periods.
02:45Moreover, it is likely that our ancestors made an excessive use of the burn to grow their land,
02:52accelerating the advance of the desert.
02:55In any case, scientists agree that this luxurious Sahara would have become a desert again,
03:01even in the absence of human intervention, a phenomenon attributed to the natural cycles of the earth.
03:07It is therefore useless to put the entire responsibility of this brutal transition on man.
03:12This change could simply reflect the interactions between vegetation and dust cycles.
03:18It remains difficult to determine the causes of these changes, as the factors are interconnected.
03:23During the last humid period, the Sahara was home to hunter-gatherers.
03:27With its gradual drying, these populations turned to farming to meet their needs,
03:33but it is just as conceivable that overgrowing has contributed to accelerating the degradation of the landscapes.
03:40So, what is the real origin of this phenomenon?
03:43The egg or the hen?
03:45In this particular case, the human or the cow?
03:48The evidence available today does not yet allow to decide.
03:52Nowadays, we can say that water is no longer an insurmountable problem in the Sahara,
03:57despite its desert immensity and the fact that the air of the green forests has changed.
04:02Technology offers unprecedented solutions, such as the Nubi Basin, the largest underground water reservoir in the world.
04:09This hydraulic treasure, located on the eastern border of the desert,
04:13extends over four countries in North-East Africa, Sudan, Chad, Libya and Egypt.
04:19It covers about 2 million square kilometers and contains nearly 150,000 cubic kilometers of underground water.
04:25It is enough to see the infrastructure deployed during its implementation.
04:29It is the largest irrigation project on the planet, making possible a prosperous life in the heart of the Sahara.
04:34But imagine living in the Sahara with a single source of water.
04:38It seems inconceivable, doesn't it?
04:40However, the ancient Garamonte have achieved this, not only by surviving, but by thriving for nearly a millennium.
04:47Despite the absence of swamps or rivers feeding their desert refuge.
04:51These ingenious pioneers were the precursors of urban life in the heart of the sands,
04:56to the point of attracting the attention of the Romans, who could only admire their genius.
05:00While many considered them as simple nomads,
05:03the Garamontes built a real empire under one of the most hostile climates on the planet.
05:08But what was their secret?
05:10They showed remarkable ingenuity by digging a vast underground network to exploit a gigantic aquifer.
05:16They literally extracted every drop of water from the depths of the dunes.
05:20But recent studies reveal that, although they were laborious and ingenious,
05:25the Garamontes also benefited from a good dose of luck.
05:29The Garamontes had an underground aquifer, which led the water to a hill,
05:33where they set up more than 500 fogueras, remarkable irrigation systems,
05:38some extending over more than 4 kilometers.
05:41These devices functioned like a straw, allowing the irrigation of their crops for nearly a century,
05:47especially since low rainfall was enough to recharge the system.
05:51However, the lack of rain eventually exhausted this aquifer.
05:55To exploit the resources again, it would have been necessary to dig more tunnels
05:59and mobilize a larger number of workers.
06:02A complex task in a context marked by food and water shortages.
06:06You can probably guess what happened to the Garamontes in such conditions.
06:10The disappearance of Garamonte culture seems to be linked to several factors.
06:14Climate change probably played a role,
06:17but it is also plausible that they overexploited their water reserves.
06:21At the time, the Sahara was a fertile region,
06:24thanks in particular to the ingenious irrigation systems put in place.
06:27However, fossil water being a non-renewable resource,
06:31the phreatic aquifers gradually dried up,
06:34seemingly precipitating the decline of this kingdom from the end of the 7th century.
06:38This decline evokes the story of someone who wins a huge pact,
06:41dilapidates his wealth and finds himself returning to a much less enviable daily life
06:46once his savings are exhausted.
06:48Moreover, even if the Garamontes had left behind them some evidence of their wisdom,
06:53it is very likely that we never managed to understand it.
06:57We do not know the language they used,
07:00and their texts remain almost entirely indescribable to this day.
07:04Let's go back to the Sahara.
07:06This desert was formed about 4,500 years ago,
07:09but today we have a fascinating view of life at this time,
07:12thanks to natural parks in Africa.
07:15These places house an extraordinary open-air art gallery,
07:18with more than 15,000 paintings and ancient engravings,
07:21illustrating the daily life of the inhabitants of some 11,000 years ago.
07:25Finally, if the engravings are not enough
07:27and you want to discover a real desert transformed into a flower garden,
07:31a trip to California is necessary.
07:33You can observe one of the most beautiful natural phenomena there,
07:36the superfluorescence.
07:38Imagine an explosion of colors,
07:40orange, green, pink,
07:42in an arid desert after several years of rain in usually dry areas.
07:47This dazzling spectacle, visible from space,
07:50makes the desert a living painting of a rare beauty.
07:53This rare phenomenon also manifests itself in other arid and desert areas,
07:57notably in West Africa and Australia,
08:00in Western Australia and Chile.
08:02These regions, where summers are arid and dry,
08:05benefit from a soft and humid air in winter,
08:08offering a perfect setting for spectacular flowering.
08:11The flower seeds buried in the sand of the desert
08:14can wait for decades before germinating.
08:17When the scorching sun eliminates all the herbs
08:20and enough rainfall comes to moisten the soil,
08:23it is as if the seeds decided that their time had come.
08:27At that moment, hundreds of thousands of tourists flock
08:31to immortalize these landscapes
08:33and share their enchanting clichés on social networks.
08:36Alas, this influx represents a serious threat to these fragile flowers.
08:40If you visit such sites,
08:42be sure not to pick them up or crush them.
08:45Stay on the marked paths,
08:47do not leave any waste,
08:49and limit yourself to taking pictures
08:51while leaving only your footsteps behind you.
08:54Is it clear?
08:55Very good!