By WANJOHI KABUKURU and SAM MEDNICK OUAGADOUGOU, Burkina Faso (AP) — A series of complex challenges, including a lack of funding and political will as well as rising insecurity linked to extremist groups al-Qaida and the Islamic State in Burkina Faso, are obstructing progress on Africa's Great Green Wall, according to experts involved in the initiative. There have been some modest gains for the project,