人类创造了撒哈拉沙漠吗?

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新的研究挑战了地球轨道变化引发撒哈拉沙漠化的观点。

-尼克·弗雷泽,Journal Development Manager,万博亚洲体育地球科学前沿

今天的撒哈拉是地球上最大、最干燥的陆地之一。然而在5000年到10000年前,通常被称为“非洲湿润期”的一段时间,撒哈拉的气候和生态系统都大不相同。而不是干旱的沙漠景观,the Sahara was characterized by lush and diverse vegetation,a consequence of monsoons and increased rainfall over the northern Africa landmass.

撒哈拉历史上这段异常潮湿的时期的结束,向现代社会过渡,长期以来一直是科学家试图了解气候和生态临界点的目标;到现在为止,most studies have pointed to changes in the Earth's orbit or natural changes in vegetation as the major driving forces.一篇新论文万博亚洲体育地球科学前沿考古学家Dr.David Wright,from Seoul National University,韩国挑战这一观点,并建议在这一时期,人类可能也在推动气候变化方面发挥了积极作用。

赖特解释说:“在非洲潮湿的时期,撒哈拉的植被状况完全不同。”"All of the plants that are found in the Sahara today were there,但是在萨赫勒也有植物,撒哈拉以南的半干旱地区,and even types of plants that are found in the Congo rainforest".这个所谓的“绿色撒哈拉”也能支撑大型动物——北非的岩画,可以追溯到这个时期,描绘鳄鱼,大象和长颈鹿,今天无法在撒哈拉地区生存的动物。

The wet conditions also had an important influence on human sustainability and cultural development,允许人类在觅食和捕鱼社区中繁衍生息。“与许多其他地方不同,撒哈拉地区的人们变得久坐不动,there was really no need for agriculture",莱特说。“生活在那个时期的人们的主要饮食之一是尼罗河鲈鱼,an enormous 150 kg fish,而这仅仅是因为撒哈拉的巨大湖泊能够养活丰富的鱼类和渔业种群”。

但这样的有利条件并没有持续下去。Although the exact timing and spatial distribution is still under debate,there is consistent agreement in geological and archaeological records that beginning approximately 8,200 years ago,the Sahara began a trend towards more and more arid conditions.在接下来的3500年里,北非的景色从多样化的,潮湿的生态系统与今天发现的情况相似。

这种干燥和沙漠化的根本原因以前是由于地球轨道的细微变化造成的,这反过来影响了大气天气模式,导致北非降雨量减少。但是莱特,他的科学研究使他在世界各地探索新石器时代的考古遗址,suggests that this is not the full picture.“在东亚,关于新石器时代的人口如何深刻地改变了地貌,以至于季风停止向内陆渗透的理论由来已久。”赖特解释说,又注意到欧洲记录了人类驱动的生态和气候变化的证据,North America and New Zealand.Wright believed that similar scenarios could also apply to the Sahara.

To test his hypothesis,Wright reviewed archaeological evidence documenting the first appearances of pastoralism across the Saharan region,and compared this with records showing the spread of scrub vegetation,an indicator of an ecological shift towards desert-like conditions.这些发现证实了他的想法;从大约8000年前尼罗河周围的地区开始,pastoral communities began to appear and spread westward,在每种情况下,同时增加灌木植被。“畜牧业和农业是嗜好。你用得越多,就越依赖它们,你越需要它们“,莱特说。

日益增长的农业成瘾对该地区的生态产生了严重影响。由于引入了牲畜,更多的植被被移除,它增加了陆地的反照率(从地球表面反射的太阳光的数量)。这反过来又充分影响了大气条件,减少了季风降雨。减弱的季风导致了进一步的沙漠化和植被损失,促进反馈循环,最终在整个现代撒哈拉地区蔓延。这个循环的核心是火在创造新的生态环境中所起的作用。尽管有证据表明在整个人类历史中都存在火灾,wild animals will not go onto a newly burned landscape because they would be easy targets for predators.然而,pastoralists direct and protect their animals onto the newly regenerating landscape,改变“恐惧的生态”,这鼓励灌木生长,而不是草。

There is much work still to do to fill in the gaps,但赖特认为,地下隐藏着丰富的信息:“此时撒哈拉地区到处都是湖泊,他们会记录下植被的变化。我们需要钻到这些以前的湖床上获取植被记录,看看考古学,and see what people were doing there".

Wright stresses that these approaches can be best achieved through cross-disciplinary efforts between archaeologists,ecologists,以及那些使用计算机模型来尝试和理解地球气候的气候科学家:“很难模拟植被对气候系统的影响。作为考古学家和生态学家,我们的工作就是出去获取数据,帮助制作更复杂的模型”。

尽管发生在几千年前,人类对环境和气候退化负有责任的含义是显而易见的。In the post-Industrial period,人类活动改变了它们的栖息地,地质学家提出了一个新的时代,“人类世”,标志着景观已被充分改变,以便在地质记录中得到明显识别的时期。

世界上大约15%的人口生活在沙漠地区,Wright stresses the importance of his findings: "the implications for how we change the ecological systems have a direct manbetx 手机客户端impact on whether humans will be able to survive indefinitely in arid environments".然而,即使我们跨过了生态临界点的门槛,Wright still sees reasons to be optimistic: "Humans evolved in the context of changing climate,在过去的六百万年里,我们的整个适应过程都是适应气候变化。As we look at the data,there is no avoiding future climate change,it's going to be severe and cause a lot of ecological stress.但我们最终是一个非常有创造力的物种,an innovative species,我们适应了气候变化。

Read the full article.

6关于人类创造撒哈拉沙漠的评论?

  1. 古斯塔夫斯95// March 16,2017 at 2:55 pm/ / 答复

    有趣的,这也意味着,我们可以朝着相反的方向,通过遵循自然法则,使撒哈拉重新焕发生机,重新焕发生机。

    Like

  2. Juan C.拉腊萨奥尼亚 April 4,2017 at 12:47 pm/ / 答复

    This is a very interesting study that can provide new insights into the interaction between humans and the environment in arid regions,对沙漠化管理的影响。In any case,应当回顾的是,人类在撒哈拉沙漠扩张中的作用最有可能是次要的,and probably restricted to speeding it a little bit.地质证据表明撒哈拉沙漠已经在中新世晚期就位(见Zhang等人,2014,自然,and its astronomically-forced "greening" and "yellowing" has been occurring well before the emergence not only of pastoralists,but also of modern humans and even of the hominin clade (see Larrasoaña et al.,2013,PLoSOne).

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    • 古斯塔夫斯95// 6月19日,2017 at 2:55 pm/ / 答复

      它在文章中说撒哈拉在5000-10000年前是湿的。

      "The Sahara today forms one of the largest and driest expanses of land on Earth.然而在5000年到10000年前,通常被称为“非洲湿润期”的一段时间,撒哈拉的气候和生态系统都大不相同。而不是干旱的沙漠景观,the Sahara was characterized by lush and diverse vegetation,a consequence of monsoons and increased rainfall over the northern Africa landmass."

      你不相信吗?

      Like

  3. 嗨,戴维,I just seen some of your comments about the sahara desert,I belive i have a simple soullition to fix it,建造一条从内陆到沙漠中心的塑料管道,then build green houses over the sea water to desalinate the water and allow the water to flow into the sand to create an artificial oasis,也许你需要挖一个洞埋一个水来保持表面的水分,我也不知道海平面会在哪里,但如果你能在海平面以下挖掘,也许可以加一个水塔,让水从海中流入沙漠中的虹吸管?

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    • 这不是一个简单的解决方案,根本不可能,the Sahara is 920.000.000 ha.big.当你看到现实时,只有管理得当的牲畜才能保持这种季节性湿润生态系统的再生和功能。这是有科学依据的,这些牲畜可以模仿撒哈拉地区曾经的巨型牛群。正是在这些畜群消失的时候,基本的生态系统功能停止工作,甜点形成了。This is because the plants (the proper word would maybe be the entire ecosystem) are depended on grazing animals to survive in these areas,and without them you have no plants,and without plants you have dessert.

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  4. 我认为在未来的几十年里,亚马逊也会发生同样的事情。为了养牛,茂密的森林被草场所取代。

    Like

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