The Great Green Wall of the Sahel and Climate Change-- More Rain or more Pain

On Monday, I went to sit in on a workshop/conference about the African Drylands and the re-greening of this area. It was very interesting and there has been much written about it:

http://www.scientificamerican.com/article.cfm?id=farmers-in-sahel-beat-back-drought-and-climate-change-with-trees&print=true

http://www.bbc.co.uk/news/10344622




What is happening is related to agro-forestry. Farmers are growing trees on their farms and it is leading to the greening of the land in the semi-arid region (the Sahel) where I am currently visiting. In addition to greening the land, it is stabilizing the soils and providing additional income to farmers. It is adding food security to the region. One speaker said that 5,000,000 hectares have been regrown over the last 30 years. There was clearly a difference.

For those of you who may not remember, the Sahelian region has undergone significant changes with a severe drying period in the 1970s and 1980s. The impact was significant with many farmers going to cities leading to urbanization. Furthermore, many lives were lost. At that time the argument went something like:

- the desertification and drought of Sahel was being caused by cattle and poor farming techniques. So in fact the drought was due to the people themselves. Early climate modeling studies seem to support this but the changes that they proposed to the land surface were much larger than observations.

It turns out that we would get a clarification on the causes of drought in West Africa until the early part of this decade. Dr Alessandra Giannini and colleagues wrote an article in Science which through global model attribution showed that the drought was caused primarily by the oceans and that global warming was in part responsible for the ocean temperature changes.

So what is the point. Well we might think that we can green the Sahel which I think is a great idea without also doing mitigation. However, this would be a grand mistake and in fact have little impact on precipitation if the global warming is accelerated or goes beyond a certain point. Estimates range from 2 degrees C-6 degrees C (3.6-10.8 F) globally.

So I applaud these efforts, but lets not fool ourselves into thinking that we don't have to mitigate globally and ultimately move away from a carbon based economy to a renewable energy based economy.

One other problem, is that governments from Sahelian countries that are not at the top of GNP list will begin sinking money into the Green Wall in the hope that their food security will increase. However, if rainfall is being controlled by sources thousands of miles away over the Indian or Atlantic Oceans what will it really mean. DEBT on impoverish countries.

Countries in Sahel did this a few years ago through rain enhancement schemes (cloud seeding). It didn't work because the scale of the rain systems here are huge compared to seeding efforts. Also the clouds also have lots of CCN and ice so trying to make more is really questionable.

Finally, it appears that we are moving into a wet period of the Sahel. Unfortunately, this area cannot handle large amounts of rain and the flooding has displaced hundred of thousands of West African residents in the last 2 years. So there is no easy answer and given that millions of people live in crowded cities -- many in poor conditions does not bode well no matter what the situation is in the countryside.