Boko Haram militants have destroyed about 1,100 schools this year in their stronghold region surrounding Lake Chad, the U.N. envoy to the region said Monday. Toby Lanzer, who became the U.N. envoy to the Sahel region of central Africa in July, said the targeted schools were in Nigeria, Niger, Chad, and Cameroon, the four countries most affected by the extremist insurgency. The group, whose name is a Hausa-language term that means "Western education is forbidden," has conducted scores of attacks on schools and universities in an insurgency that has killed at least 17,000 people since 2009. Fighting between Boko Haram terrorists and government soldiers has forced more than 2.6 million people from their homes, including 2.2 million Nigerians, Lanzer said in Geneva, following a tour of the Lake Chad basin region. The U.N. envoy emphasized that while Boko Haram refugees were not currently a significant contributor to Europe's migrant crisis, the situation could change if conditions around Lake Chad remains grave.