a Figure 9.2 (a) Global distribution of hyperarid and dryland areas Drylands Dry subhumid areas Dry subhumid areas DrylandsSemiarid areas AridSemiarid areas areas DrylandsDryDry subhumidsubhumid areasareas HyperaridArid areas areas SemiaridSemiaridDryDry subhumidsubhumid areasareas areasareas AridArid areasareasHyperarid areas SemiaridSemiarid areasareas HyperaridHyperarid areasareas Map produced by ZOÏ Environment Network, September 2010 Source: UNEAridAridP W orld areasareas Conservation Monitoring Centre DrylandsHyperaridHyperarid areasareas Map produced by ZOÏ Environment Network, September 2010 MapMap producedproduced byby ZOÏZOÏ EnvironmentEnvironment Network,Network, SeptemberSeptember 20102010 Source: UNEDryP subhumidWorld Conservation areas Monitoring Centre Source:Source:b UNEUNEPP WWorldorld ConservationConservation MonitoringMonitoring CentreCentre DrylandsSemiarid areas Arid areas Figure 9.2 DryDry subhumidsubhumid areasareas Hyperarid areas SemiaridSemiarid areasareas (b) Regions MapMap producedproduced byby ZOÏZOÏ EnvironmentEnvironment Network,Network, SeptemberSeptember 20102010 Source:Source: UNEUNEPPAridArid WW areasorldareasorld ConservationConservation MonitoringMonitoring CentreCentre vulnerable to HyperaridHyperarid areasareas Map produced by ZOÏ Environment Network, September 2010 Source: UNEP World Conservation Monitoring Centre desertification MapMap producedproduced byby ZOÏZOÏ EnvironmentEnvironment Network,Network, SeptemberSeptember 20102010 Source:Source: UNEUNEPP WWorldorld ConservationConservation MonitoringMonitoring CentreCentre Vulnerability Other regions Figure 9.3 Classification of hyperarid and dryland areas TYPE AND EXAMPLES ECOSYSTEM CLIMATE AREA PERCENTAGE LENGTH OF OF HYPERARID AND (million square GROWING DRYLANDS kilometres) SEASON (days) Hyperarid Desert No seasonal rainfall pattern. 9.8 6.6 Nil (Sahara Desert, Africa; Very little human activity Gibson Desert, Australia) possible. Arid Semi-desert Annual precipitation highly 15.7 9.6 1–59 (Sahel region, Africa; variable. Average between 200 Patagonia, South America) and 300 millimetres Semiarid Grasslands Highly seasonal rainfall between 22.6 15.2 60–119 (Mongolia, Asia; western 500 and 800 millimetres. New South Wales, Australia) Moderately variable from year to year. Land cover change: desertification Dry subhumid Rangelands* Rainfall more reliable and 12.8 8.7 120–179 u (south-west Western Australia; rain-fed** agriculture widely mid-west region, U.S.A) practised. 60.9 (total) 40.3 (total) CHAPTER 9 *Rangelands are places where there is a mixture of grasses, shrubs and scattered trees. **Rain-fed farming relies totally on rainfall and there is no irrigation. 121.