Researchers say the Sahara desert is expanding at a rapid rate with Sudan, Chad, Mauritania and Libya expected to bear the brunt

LONDON, March 29 (Thomson Reuters Foundation) - The Sahara desert has expanded by 10 percent in the past century - partly because of climate change - with far-reaching impacts on communities surrounding it, researchers said on Thursday.

Sudan, Chad, Mauritania and Libya are some of the countries which will bear the brunt of the desert's expansion, researchers at the University of Maryland said.

Two-thirds of the desert's growth is a result of natural climate cycles, while the remaining one-third stems from climate change, the researchers said in a report published in the Journal of Climate on Thursday.

"This is a natural disaster unfolding slowly," said Sumant Nigam, a professor at the University of Maryland.

"Desert advances don't get the same headlines for relief" as other major disasters like hurricanes, Nigam told the Thomson Reuters Foundation.

The Sahara is the world's largest warm weather desert - the Arctic basin and Antarctic continent are both much larger deserts, categorised as having a maximum 100 mm of rain a year.

Other deserts may also be expanding, according to the study which the researchers say is the first to assess century-scale changes to the Sahara's boundaries.

Like all deserts, the boundaries of the Sahara fluctuate with the seasons, expanding in the dry winter and contracting during the wetter summer.

The Sahara's biggest growth has occurred along the desert's northern and southern borders, the study said.

The Atlantic Multidecadal Oscillation (AMO), a natural climate cycle, had the largest impact on the Sahara's expansion, the study said.

AMO causes the northern Atlantic Ocean to flip between warmer and colder phases over a 50 to 70 year span, bringing more drought or rain to the African continent.

Human activity too has played a role, the study said.

"The trends in Africa of hot summers getting hotter and rainy seasons drying out are linked with factors that include increasing greenhouse gases and aerosols in the atmosphere," Ming Cai, a programme director in the Virginia-based National Science Foundation, said in a statement.

"These trends also have a devastating effect on the lives of African people, who depend on agriculture-based economies," Cai said.