CHINGUETTI — Muhammad Gholam el-Habot, a 50-year-old bookkeeper in the Mauritanian town of Chinguetti, is working to preserve about 1,400 ancient manuscripts in his family's library as desertification and extreme weather threaten their survival. He took over responsibility for the collection in 2002 when his father became sick.

The el-Habot family library is one of a handful of its kind still operating in Chinguetti, a medieval fortress town, or ksar, in Mauritania's northern Adrar region. Between the 13th and 17th centuries, the town was a center of commerce and Islamic learning, located at the crossroads of trans-Saharan trade routes linking the Sahel and the Maghreb. In West African lore, it was referred to as Islam's seventh holiest city, and UNESCO, which granted World Heritage status to Chinguetti and three other Mauritanian ksour in 1996, nicknamed it the "Sorbonne of the Sahara."

Generations of scholars collectively amassed about 6,000 scripts covering Islamic jurisprudence, hadith, mathematics, medicine and poetry, stored in roughly 30 libraries that were open to people from around the world. Some of the manuscripts were authored by Chinguetti scholars, including Sidi Mohamed Ould Habot, who wrote about the science of poems.

Mauritania is 90 percent Sahara desert and has faced desertification for centuries. Annual rainfall in the country has decreased by 35 percent since 1970.

"Extreme heat and less predictable rainfall patterns means that texts are increasingly damaged by water or heat, making many manuscripts beyond repair. More than that, the mud libraries themselves are not built for sudden rain and longer summer of over 40 degrees (Celsius, or 104 degrees Fahrenheit)," said Andrew Bishop, a researcher at the University of Wyoming.

Many of Chinguetti's 4,500 residents now live in cement buildings outside the original confines of the abandoned ksar, which covers an area of about 500 square kilometers (200 square miles). Residents of the old town are allowed to renovate buildings only minimally to preserve the original stone architecture and typical Moorish structuring. Younger residents have moved to Nouakchott or other locations to explore economic opportunities. "Chinguetti's decline is largely due to the lack of support for its traditional lifestyle," Bishop said.

El-Habot said the manuscripts in his care carry deep personal meaning. "These books are very important to my family and me. My relationship with them is like that of a father and his son," he said. "We must protect them until God takes the land and all the people who are on the land."