Eleven African countries are moving ahead with an ambitious pan-African effort in the Sahel-Saharan region of the continent to protect arable land from the encroaching Sahara desert—by planting trees.     The countries—Djibouti, Eritrea, Ethiopia, Sudan, Chad, Niger, Nigeria, Mali, Burkina Faso, Mauritania, and Senegal—came together in 2007 to execute the $2 billion dollar project to arrest the creeping desertification … Lees verder