Feb 7, 2012

Back When Sahara Was Green and Fertile

Sahara! For everyone, this word evokes the desert: a desert of sand and stone, with hot sun, a world almost barren, hot and dry to the destruction of every living thing. The obstinacy with which we cling to this image, remember that the Sahara is still alive – some animals and plants adapted to these extreme miracle – that there are oases where water feeds plantations, animals and humans and protects the centuries life settlements.

More than we could imagine the whole Sahara as a green and fertile plains. However, this land, which is now for us all, Desert, was once – in a few thousand years ago – a huge green expanse, replete with vigor, swarming of animals and inhabited by people who enjoyed this abundance and living on her account. What happened to that haven?

Last time the luxuriance of the Sahara lasted about 7,500 years ago until about 3,000 years ago. But, as we may seem unusual compared to the current state of this region, there was a unique event. It was an episode of a “serial” number of such successive periods in geological history of the region. Phases in the Sahara was green and wet alternating with dry periods, the Sahara desert that appearance gained him know today, became a desert sometimes even larger than today.

With geological data, scientists were able to identify several so wet periods, three of which were followed in North Africa during the last 120 thousand years and have had a significant impact on biodiversity of the three continents of the Old World.

  • Pluvialul Abbassia started about 120,000 years and took that. 30,000 years.
  • There followed a long drought, which, 50,000 years ago, the Upper Paleolithic, began a new period of heavy rains, which lasted approx. 20,000 years ago, ending 30,000 years ago.
  • The most recent wet period occurred in the Neolithic Age, Neolithic subpluvialul call specialists. In the meantime, high precipitation fell (though not as abundant as in the two previous wet periods, hence the name given subpluvial rainy latter period). Subpluvialul Neolithic occurred after the last glacial period, because it was, say climate scientists, Earth’s axis tilt changes, the nearest planet to the Sun, enough to increase temperatures. Paradoxically, getting more sun, the Sahara became wetter, training monsoon: air over land, heating, rises, being replaced by air came from the ocean, cooler and wetter, which brought rain. These changes in monsoon regime have made for thousands of years, these moist winds bring abundant rainfall over the Sahara.

Since seven millennia ago, this phenomenon was strong (with heavy falls of rain) for 2000 years, after which the intensity decreased gradually until the installation of dry periods, the latter by ca. 3,500 years. Since then, the region has gradually aridizat and Sahara (re) became the desert we know today.

During the latter period wet and human civilization in North Africa had grown considerably, and the latter rain had great importance for humans in this region. In his time flourished settlements and human activities. After him, from one century to another desert expanded, forcing people to retreat to the edges of the Sahara or to take refuge in the few remaining green oasis.

But, in the several millennia of abundance, this region would have seemed a paradise to anyone living flaring. Lakes were much higher, there were many rivers and green vegetation, lush plains and hills covered. In the middle of the desert highlands, today some barren hills and rocky slopes were covered with forests of oak and walnut, linden and elm, olive and pine ienuperi says Roland Oliver, professor of African history at the University of London. Waters full of fish flowing through the grass fields, the extent to which swarmed million animals.

Elephants, giraffes, buffalo, all kinds of other herbivores thrived on account of lush greenery, whose growth was supported by the abundance of rain. Sahara was a savannah vibrating with life, as today’s savannahs of Africa in the rainy season.

Samples of rock art preserved until today, as are the famous frescoes of the Tassili n’Ajjer (Algeria) or the Akakus (Libya) show that in those areas – now in full desert and hot – such living animals: some of them can be easily recognized in the representations of the surface rocks.

Then green Sahara and species housed in the meantime disappeared interesting representatives of megafauna, such as Sivateherium and Pelorovis.

Sivatherium was a towering herbivore, a relative of the giraffe, okapi somewhat similar to today (another mammal related to the giraffe). Sivatherium have, however, that feature two pairs of “horns” bone of the skull bone extensions – some straight, as giraffe horns are present, but longer, and two behind them, expand on, giving the animal a unique look, unusual even among today’s species.

As Pelorovis, it was a species of wild cattle, impressive length of his horns, four feet.

Both these species have disappeared behind approx. 5000 years, probably due to changes in habitat, the transformation of green heaven in hell when hit by the sun today.

This sequence of states of the region Sahara, the desert plain mănoasă, favored, say experts, animal and plant species spread from Africa to Eurasia and vice versa (the land bridge connecting two continents today, in northeast Egypt) which explains the existence of species common to both continents. The so-called Saharan pump theory: in the rainy, animal populations remained isolated in the valleys of the rivers or something more hospitable areas, distant from each other, while in rainy periods, the species is spread easily large areas of each continent and could even migrate from one continent to another.

5 people millennia ago Sahara lived in settlements built on the shore waters, enjoying an abundance of fish, shellfish, waterfowl and various mammals, their food. These coastal communities engaged in intense activity of hunting and fishing, gathering wild plants (including cereals), pottery and manufacturing tools. There was controversy among experts on the lifestyle of these populations, were hunter-gatherers and farmers, sedentary or nomadic? The latest findings suggest that there were hunters-gatherers who were completely sedentary.

But as wet climate was replaced by the desert populations have adapted to new ways of life, becoming more sedentary and grabbing the animal husbandry and cultivation of plants. Very sparsely populated today, still holds Sahara settlements, even in arid regions, witness the power of the human species to adapt to difficult conditions.

Is recent climate change, which will likely lead to desertification of much of the southern Europe in the coming decades, we will require an effort similar adaptation?

Unlike Neolithic people we are, it seems, partly responsible for what happens to Earth’s climate. You will need a more complex adaptation – technological, social, cultural – to meet this challenge. The corrective measures will be necessary to readjust what we ourselves have disturbed the balance of the planet, and accepting the challenge and adjust our way of life, to the extent that changes are the result of natural phenomena related to cosmic cycles. From energy to agriculture, from migration to the cuisine, many will change later this century and the world for over a century might look like it is now as much as like the Sahara arid and hot today with the green, wet and fertile five millennia ago.

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