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Guardian Article

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Imagine a green wall - 15km wide, and up to 8,000km long - a living green wall of trees and bushes, full of birds and other animals. Imagine it just south of the Sahara, from Djibouti in the Horn of Africa in the east, all the way across the continent to Dakar, Senegal, in the west.

The building of this pan-African Great Green Wall (GGW) was approved by an international summit this week in the former German capital Bonn, a side event of the joint conference of the committees on science and technology and for the review of the implementation of the UN Convention to Combat Desertification (UNCCD).

The GGW, as conceived by the 11 countries located along the southern border of the Sahara, and their international partners, is aimed at limiting the desertification of the Sahel zone. It will also be a catalyst for a multifaceted international economic and environmental programme.

The Sahel zone is the transition between the Sahara in the north and the African savannas in the south, and includes parts of Burkina Faso, Chad, Djibouti, Eritrea, Ethiopia, Mali, Mauritania, Niger, Nigeria, Senegal and Sudan.

The GGW initiative initially involved the planting of a 15km-wide forest belt across the continent, with a band of vegetation as continuous as possible, but rerouted if necessary to skirt around obstacles such as streams, rocky areas and mountains - or to link inhabited areas.

During the meeting in Bonn, the Global Environment Facility (GEF) confirmed its promise to allocate up to $115m to support the construction of the green wall. Other international development institutions also made investment pledges to support building the wall, of up to $3bn.

The GEF - formed by 182 member governments, numerous international institutions, non-governmental organisations and the private sector - provides grants to developing countries and those with economies in transition for projects related to biodiversity, climate change, international waters, land degradation and the like.

"The Green Wall should be seen as a metaphor for the co-ordination of a variety of international projects, for economic development, environmental protection, against desertification, and to support political stability in the heart of Africa," said Boubacar Cissé, African co-ordinator for the UN secretariat against desertification.

The GGW was first proposed in the 1980s by Thomas Sankara, then head of state in Burkina Faso, as a means to stop the growing of the Sahara. The idea was voiced again about 20 years later by the then Nigerian president, Olusegun Obasanjo, who presented it to the African Union (AU) in 2005.

Since then, the project has gained international support outside Africa.

The GGW would have numerous advantages. Other than stopping desertification and erosion, the wall would protect water sources, such as Lake Chad, which has been drying up for decades, and restore or create habitats for biodiversity.

In addition, the wall would provide energy resources; fruit, vegetables and other foodstuffs; support local economic development; and even political stability in the whole region, said Daniel André, of the UNCCD.

"The construction of the Great Green Wall across Africa should be the motor for international co-operation, both at the national and at the communal level, with the objective of fighting poverty," André, who is from Senegal, told IPS.

"The objective of the project is more than stopping desertification," he added. "It goes straight to the heart of the fight against poverty: it must provide people across the continent with an economic perspective to stop the youth migrating from the region, it must provide the region with a cushion against climate change, and by so doing also help to restore political stability."

André said that political stability is most important now, given the present political turmoil in the Arab world - an immediate neighbour to all 11 countries involved in the construction of the GGW.

Bernd Wirtzfeld, of the German ministry for economic co-operation and development, said that international donors were ready to support the project.

"In its current design, GGW is much more than its name or its trajectory suggest," said Richard Escadafal, chair of the French Scientific Committee on Desertification. "Its aim is to ensure the planting and integrated development of economically interesting drought-tolerant plant species, water retention ponds, agricultural production systems and other income-generating activities, as well as basic social infrastructures," Escadafal said.

Escadafal also pointed out that beyond the technical problems associated with the initiative, "its success considerably depends on the social setting in which these plant propagation and tree planting projects are conducted".

"Projects in which reforestation was put in practice without the participation of local inhabitants were almost always limited and non-sustainable," Escadafal warned. "When farmers' rights and what they could hope to get back from their labour remain uncertain, technical efforts to select the best species, to enable them to develop properly in modern nurseries using advanced planting techniques, could generate some good results, but only in the short term."

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Julio Godoy for IPS, part of the Guardian's Development Network

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Great Green Wall to Stop Sahel Desertification | Julio Godoy

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Imagine a green wall - 15km wide, and up to 8,000km long - a living green wall of trees and bushes, full of birds and other animals. Imagine it just south of the Sahara, from Djibouti in the Horn of Africa in the east, all the way across the continent to Dakar, Senegal, in the west.

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This is the process that sees productive land turned into non-productive desert. It usually affects dry areas on the edge of deserts, eg The Sahel, south of the Sahara Desert in Africa.

What causes desertification?

Desertification is a complex process. It is caused by physical processes and human mismanagement. Factors which may cause desertification include:

Climate change - especially long dry periods, causing drought. The dry conditions cause the vegetation to die, so the land loses the protective cover that vegetation provides.

Too many animals within the area - leads to overgrazing.

Population growth - traditional, less intensive, methods of farming decline. There is more pressure on the land for growing crops. Nomadic tribes that once moved around may start to farm in one area. Marginal land that is less suitable for farming is used. Wood is also used for buildings, heating, and firewood, causing deforestation and soil erosion.

What are the effects of desertification?

Lack of vegetation cover for holding soil together and for grazing.

Increased soil erosion.

Crop failure, leading to famine.

Fewer plant and animal species.

Land is unable to support people so they are forced to migrate.

How can desertification be solved?

Reduce grazing - so plants have a chance to grow again.

'Magic stones' - circles of stones are placed on the ground to hold water on the soil rather than let it run quickly across the surface. This reduces soil erosion.

Planting trees - providing shelter from the wind.

Mulching - adding layers of leaves or straw can reduce evaporation and add nutrients to the soil when they rot.

Terracing or contour ploughing - soil is not washed down the slope when it rains.

Drought-resistant plants - used to stabilise sand dunes.

Recent evidence suggests that there are some areas where the process of desertification has slowed down. However, the areas on the edge of deserts are still fragile and need very careful management.

More from Extreme environments :

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BBC - KS3 Bitesize Geography - Extreme environments : Revision, Page 10

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This is the process that sees productive land turned into non-productive desert. It usually affects dry areas on the edge of deserts, eg The Sahel, south of the Sahara Desert in Africa. Desertification is a complex process. It is caused by physical processes and human mismanagement.

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Nigeria

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WaterAid is an international charity that transforms lives by improving access to safe water, hygiene and sanitation.

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How to fight desertification and reverse climate change

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Allan Savory: How to fight desertification and reverse climate change

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"Desertification is a fancy word for land that is turning to desert," begins Allan Savory in this quietly powerful talk. And it's happening to about two-thirds of the world's grasslands, accelerating climate change and causing traditional grazing societies to descend into social chaos. Savory has devoted his life to stopping it.

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Analysis: Understanding the Sahel drought

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Food and water shortages have left a trail of death and destruction in the Sahel [Reuters]

Between the vast Sahara Desert and the dense foliage of the African Rainforest is a band of semi-arid grassland. Known as the Sahel, this hardy landscape is one of Africa's most productive crop regions.

But the crops in the Sahel are grown close to their limits of tolerance, and rely on natural rainfall. This means that even small changes to the amount of rain can have disastrous effects.

Unfortunately, this is a region which often suffers highly erratic rainfall.

Droughts in the Sahel don't last a month or a year, they last for decades. And these long droughts have occurred regularly over the past 12,000 years.

The region is in one of these droughts now - scientists say it started in the 1960s.

Research by the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) at the University of Washington shows the amount of rain received each year in the Sahel region, compared with the average.
The bars reaching upwards from the centre indicate more rain than average. Those which are drawn downwards, indicate a decrease. Simply, the longer the line, the greater the deviation from the average.

Between the 1950s and 1960s, there was plenty of rain across the Sahel, but just before 1970, a new drought started.

With the exception of a period of five years, all years since have seen a deficiency of rain.

The most severe drought was in the 1980s and, since then, levels of rainfall have recovered a little. However, rainfall remains significantly below the average for the past century.

The rain across the Sahel spreads up from the south during the summer months. The onset is usually in June, with the majority of the rain falling between July and September.

Overall, the amount of rain received in the 2011 monsoon was near normal, but this doesn't tell the whole story: the rains were patchy and irregular, slow to get going, and retreated very quickly. This left many regions facing water and food shortages.

Reasons for the drought

Compiling reasons for the drought is difficult, but what is known is that the rainfall across the Sahel is driven by three factors:

Tropical convection: the huge towering thunderstorms that build quickly in tropical places.

The West African Monsoon: rains which starts to spread across the Sahel in June.

El Niño: the effects of the warming of the Pacific, which also affects the weather around the globe.

But there is little understanding of how these factors link together and how they are affected by the changing climate.

In the 1970s it was widely believed that the drought was caused by the farmers in the regions, blaming them for the degradation of the land and the desertification. However, subsequent studies have disproved this idea.

Currently, the most convincing theory is that the recent drought could be due to the change in temperature of the surrounding oceans.

At the end of the 1900s, the south Atlantic and the Indian Ocean warmed quickly, which reduced the difference in temperature between the land and the sea. This may have caused the monsoon to weaken and the thunderstorms to remain to the south.

When the rains do fail, there is concern that this could trigger a knock-on effect in the years to follow.

Less rain means less vegetation, which will lead to a change in colour of the ground. Instead of lush fields of plants colouring the earth in a deep green, which absorbs sunlight, the ground instead would be a lighter, barren beige, which reflects more sunlight.

This, in turn, would mean the temperature difference between the land and the sea was diminished, and would lead to further weakening of the monsoon.

To the future

It is most important to predict what will happen in the future, but currently it is almost impossible.

The difficulty is due mostly to the scant availabilty of historical data from across the region. Therefore, discovering how the climate is changing is an uphill struggle.

The current thought is that the Horn of Africa will become wetter, but what will happen across the Sahel is unknown: will it become wetter or drier? No one can be sure.

What is expected is that the rainfall will become more sporadic, bringing an increase in the number of both droughts and floods across the region.

The 2012 forecast

The monsoon forecast for the Sahel region has just been issued by the African Centre of Meteorological Applications for development (ACMAD). This is the consensus forecast for the region, drawing together forecasts from many different countries.

The forecast focuses on the months of July to September, when the majority of the rain falls across the region.

This year, the forecast suggests that the majority of the Sahel will experience average rainfall, or even above average in some locations.

The exception is the Western Sahel, which is only estimated to receive 70 - 90 per cent of their annual rainfall, and here the onset of the rains is likely to be delayed.

This means that Senegal, southeastern Mauritania, Western Mali and Gambia are all likely to face severe disruptions.

Farmers in these regions are being encouraged to prioritise crops and sow water-stress resistant seeds.
What happens next
Clearly more research is desperately needed - because even small changes in rainfall, both timings and amounts, can have dire impacts on the people who live in the Sahel.

To try to ensure that national governments have access to the best scientific information available, Africa Climate Exchange (Afclix) has recently been launched by a team led by the University of Reading's Dr Rosalind Cornforth.

Not only does the site help ensure that policy makers have direct access to the latest forecasts, but Afclix helps different research teams with varying expertise connect with each other, enabling collaborations and cross-disciplinary research.

The more studies carried out, the greater the chance there is of discovering the secret of the Sahel rains.

As the knowledge grows, the forecasts will improve and the impacts on the local population can be minimised.
Steff Gaulter is Al Jazeera's senior meteorologist. Follow her on Twitter: @WeatherSteff

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Analysis: Understanding the Sahel drought

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Between the vast Sahara Desert and the dense foliage of the African Rainforest is a band of semi-arid grassland. Known as the Sahel, this hardy landscape is one of Africa's most productive crop regions. But the crops in the Sahel are grown close to their limits of tolerance, and rely on natural rainfall.