The Great Wall of China was designed to keep out Mongol hordes, but the Great Green Wall of Africa faces an even more formidable opponent, the Sahara Desert.

The shifting sands of the Sahara creep ever southward into the Sahel, swallowing up what was once farm, forest and field. But African nations are uniting to halt the desert's advance by planting trees in an east to west line starting in Senegal, then passing through Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Sudan, Eritrea, Ethiopia, and ending in Djibouti.

BLOG: Stopping Desertification in Africa With a 'Great Green Wall'

When completed the wall will be more than nine miles wide and 4,750 miles long. The AFP recently ran an article looking at Senegal's contribution to the wall.

Hardy, drought-resistant acacia trees now dig their roots into 330 miles of northern Senegal's Tessekere-Widu rural region. Planting began in 2008.

BLOG: Man-Made Oasis Will Transform the Desert

The Senegalese government is mostly footing the annual $2.1 million bill, and it's going to take more than $200 million to complete just Senegal's portion, Matar Cisse, head of the national Great Green Wall agency, told the AFP. But the country's president seems to admire the project's audacity.

"It is a crazy project, but a touch of madness helps when conceiving something which has never been conceived," Senegalese President Abdoulaye Wade said when he launched GGW at a conference of Sahel countries in 2005.

The entire wall will cost billions of dollars. International agencies have pledged more than three billion so far.

Money spent on trees may be an investment in the region's future, considering that a United Nations report warns that two thirds of Africa's farmland may be devoured by the Sahara by 2025.

The Wall is also creating jobs and proverbial money-trees for locals. The area where the Wall is being planted has also sprouted nurseries for the acacia trees. Local women also cultivate their own livelihoods in nearby fruit and vegetable gardens.

BLOG: Ancient Desert Oasis Echoes Eden

The trees have even become something of a tourist attraction. Hundreds of Senegalese students and foreigners visit Tessekere every year to plant trees.

But it's not all blue skies for the green wall. Lamine Gueye, a Senegalese professor, worries that more trees means more shelter for malaria mosquitoes. On the other hand, he notes that the scientists and medical experts flocking to the area provide free medical care to locals.


IMAGE 1: Acacia tree at sunrise (Wikimedia Commons).

IMAGE 2: The Sahara Desert in Senegal (Wikimedia Commons).

IMAGE 3: Acacia tree at dusk (Wikimedia Commons).