Friday, July 17, 2009

The Shrinking Sahara

One of the major arguments of those who argue about the perils of increased global warming is that there are almost no beneficial aspects to the transition to a warmer planet. In the process they therefore often ignore news that argues to the contrary. Consider the BBC story that indicates that the Sahara might be turning greener.
It has been assumed that global warming would cause an expansion of the world's deserts, but now some scientists are predicting a contrary scenario in which water and life slowly reclaim these arid places.

They think vast, dry regions like the Sahara might soon begin shrinking. The evidence is limited and definitive conclusions are impossible to reach but recent satellite pictures of North Africa seem to show areas of the Sahara in retreat.

It could be that an increase in rainfall has caused this effect
There is in the story the possibility that the changing climate might improve things, but the story notes
Droughts over the preceding decades have had the effect of driving nomadic people and rural farmers into the towns and cities. Such movement of people suggests weather patterns are becoming dryer and harsher.

The Intergovernmental Panel on Climate Change warned recently that rising global temperatures could cut West African agricultural production by up to 50% by the year 2020.

But satellite images from the last 15 years do seem to show a recovery of vegetation in the Southern Sahara, although the Sahel Belt, the semi-arid tropical savannah to the south of the desert, remains fragile.
To show you how wrong this picture is, relative to reality, go to the little Google box on the top right of your screen and type “record harvest sahel.” You will find the weather and crop situation reports for the Sahel The Sahel runs 2,400 miles (3862 km) from the Atlantic Ocean in the west to the Red Sea in the east, in a belt that varies from several hundred to a thousand kilometers (620 miles) in width, covering an area of 3,053,200 square kilometers (1,178,800 square miles). It is a transitional ecoregion of semi-arid grasslands, savannas, steppes, and thorn shrublands lying between the wooded Sudanian savanna to the south and the Sahara to the north. The countries of the Sahel today include Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Sudan, and Eritrea. (Wikipedia)

Source Sahel Crop Report (pdf)

There was a record harvest in the region in 1999. This was succeeded by even greater production results in 2001 when Chad had a record harvest, as did the Gambia and Burkina Faso, Mali had a good harvest, and Niger one that was above average. Guinea Bissau had a reduced harvest.

In more recent years the problem has been that the cheapness of international imports has brought prices down below those of crops grown locally, together with an increase in international aid. Yet the crops that have been produced have led to bumper crops, consider last year.
DAKAR - Poor people in Africa's arid Sahel region will go without food despite bumper harvests this year, as wild price moves on world markets put staple cereals beyond many families' budgets, aid agencies say. Prices of imported foods have ballooned in recent years, pushing up prices for locally grown crops even though harvests are expected to be bigger than ever after abundant rains.

"The nature of food insecurity has changed in West Africa," Alexander Woollcombe, Food Security Advocacy Advisor at Oxfam GB told Reuters. "It's not a problem of production. The problem is, poor people can't afford to buy it."

Oxfam expects cereal production across five countries in the dry Sahel belt south of the Sahara -- Burkina Faso, Mali, Mauritania, Niger and Senegal -- will be a record 18.5 million tonnes this year, but the food on sale will be beyond the budget of many in these, some of the world's poorest countries
Projections of a record grain harvest for the 2008/09 growing season are being borne out, with total output for the Sahel and West Africa estimated at 54 million MT, including 9 million MT of rice and 45 million MT of coarse grains. Grain production in the Sahel is estimated at 15, 500,000 MT,1 up 21% from last year (2007/2008) and 24% above the five-year average.

Virtually all countries in the Sahel are reporting sizeable increases in rice production. On average, output was up 34 percent in 2008/09, or more than 530,000 MT greater than that of 2007/08. Good climatic conditions and the stability of local markets reflecting similar international market trends bolstered grain production in general and rice production in particular. In addition, government incentives helped reinforce and strengthen the capacity of local farmers through specific agricultural revitalization programs, subsidies and distributions of free supplies of farm inputs, fiscal measures, etc.

Back in 2002 there was this:
New Scientist has learned that a separate analysis of satellite images completed this summer reveals that dunes are retreating right across the Sahel region on the southern edge of the Sahara desert. Vegetation is ousting sand across a swathe of land stretching from Mauritania on the shores of the Atlantic to Eritrea 6000 kilometres away on the Red Sea coast.

Nor is it just a short-term trend. Analysts say the gradual greening has been happening since the mid-1980s, though has gone largely unnoticed. Only now is the evidence being pieced together.

It has been reported that by 2002 the Sahara had been reduced in size by 300,000 sq. km. as a result of these trends, which (as the current BBC story notes) have continued.

The problems of the Sahel are those of too large a population, and the impact that reliance on overly cheap imports of food have, to the detriment of local farmers. The changes due to the climate have brought about record harvests and greater areas available for agriculture.

But those benefits will not be reported with as much vigor as the problems that the region has, and the negative aspects of climate change the BBC article, for example, suggests, contrary to the evidence, that there has yet been little improvement in the conditions. Instead they concentrate on the artificial reduction in the desert that the Egyptians are trying
Thanks to the work of people like Mr el-Baz, the greening of the desert is happening in Egypt in a controlled way.

Out of the newly irrigated desert we now see the commercial growing of oranges, limes and mangoes.

Further, the Egyptian government is actually sponsoring people to settle in the desert to farm, using the water supply they can now tap into and pump out from under the sand.

The programme is part of an ambitious and controversial plan to reclaim 3.4 million acres of desert.

In either case changes in the climate are bringing demonstrable benefits, a pity that we don’t hear more of them, or that the BBC does not read its own archives.


  1. Hi Dave,

    Basic knowledge of meridional circulation tells you that deserts shrink as temperatures rise and circulation slows down. During the first millenia of the Holocene a good part of what are today the Shara and Arabia were green. It is no incendent that Agriculture took some of its first steps there. Remember were wrtting was born?

    In 2000 the finding of 200 burial sites in northern Niger shed some light on the size of the civilization once existed where today there's nothing but sand:

    There's some loose information on the internet on this period that lasted during the first half of Holocene:

    Before AGW became a political issue this was common knowledge, as some old books show:

  2. Luis:
    Thanks for the references. One of the folk that plots the old water courses under the desert is one of our grads, (Farouk el Baz) - albeit before my time, and he has been very successful at it.

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