Increases in shrub cover in arid deserts and shrublands have been recorded in the North American drylands , the Namib desert , the Karoo , north and central Mexico , large parts of the West African Sahel with some local exceptions  and Central Asia . Increasing woodiness in the Namib is consistent with an increase in rainfall extremes and westward expansion of convective rainfall . Increasing rainfall and rising CO2 concentrations  benefits some shrubs . Together with changes in land use , improved land management  and improved irrigation , this contributes to woody cover increases. Extensive woody encroachment has been recorded in savannas  in Africa , Australia , and South America  . Following drought in the Sahel , a rainfall increase since the mid-1990s has been linked to increases of woody cover between 1992-2011/2012 . See SRCCL Section 3.2.1.1 for an evaluation of the normalized difference vegetation index  and remote sensing approaches used in these studies. Tree regeneration by farmers has also increased woody cover, particularly next to villages  . Otherwise, savanna encroachment has been attributed to combinations of increased rainfall , warming  and CO2 fertilization  interacting with changing land use , where herbivory and fire regimes are altered . In some cases, woody increase has been balanced locally by changes in runoff  or by land clearing and fuel wood harvesting, as seen in western Niger, northern Nigeria, and at the periphery of major towns .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report