FAO Completes World’s First Global Assessment of Drylands Forests

Larch forest Mongolia - FAOThe UN World Food and Agriculture Organization (FAO) is drawing attention to the potential of forestation initiatives to substantially improve drylands ecosystems and the lives of some 2 billion people living in them, 90 percent of whom live in developing countries.

FAO’s ¨Trees, forests and land use in drylands: The first global assessment¨ serves as a milestone in drylands and forestry research, as well as a valuable reference for research and policymakers amidst worldwide efforts to improve livelihoods and address the impacts of climate change, drought, desertification and land degradation.

Releasing preliminary findings July 19, researchers determined that drylands make up about 41 percent of the world’s land surface, Highly variable densities of trees cover 1.11 billion hectares of these drylands, a shade less than one-third the total. That’s a land area more than twice the size of Africa.

Improving drylands ecosystems and livelihoods

Forests, in turn, are found on nearly 18 percent of drylands globally, according to the study, providing essential natural resources for the estimated 2 billion people living in them. That said, “surprisingly little is known about such ecosystems in drylands, despite widespread recognition of the need to restore [them],” FAO highlights in a news article.

FAO World Drylands MapTrees are a source of fruit, nuts, seeds, leaves and timber for construction and fuel for agrarian drylands communities. They also provide vital sustainable ecosystem services, such as retaining water, adding to and improving soils, preventing soil erosion and raising ecosystems productivity and diversity.

Already scarce, access to water will be an increasingly pressing need and concern for drylands communities amidst climate and land use change. The poor in remote rural areas will be most vulnerable not only to lack of access and drought but to food shortages as well, according to the FAO. That raises the prospect of growing conflict, social upheaval and forced migration, which is already occurring in Africa and western Asia.

Lack of timely, reliable, comprehensive data and information regarding trees and forests and dryland regions have hindered efforts to address these pressures and resulting threats. The FAO’s study fills this gap. More than 200 land and land-use experts contributed to the study, making use of satellite imagery and a new survey methodology. The full report will be released later this year.

Key preliminary findings

Drylands the world over fall into one of four categories based on how arid they are. As FAO explains, most drylands are found in two of them:

  • the dry subhumid zone – the least arid of the four zones – and consists mostly of the Sudanian savanna, forests and grasslands in South America, the steppes of eastern Europe and southern Siberia, and the Canadian prairie. Most dryland forests occur in this zone, as do some large irrigated, intensively farmed areas along perennial rivers;
  • at the other extreme, the hyperarid zone is the driest zone and it is dominated by desert – the Sahara alone accounting for 45 percent, and the Arabian desert forming another large component.

The researchers studied satellite images of more than 200,000 samples, approximately 0.5 hectare drylands plots from sources available to the public, such as Google Earth, Bing Maps and others. The resulting report “provides governments, donors, and other stakeholders in sustainable development with a valuable tool to guide policy-making and targeting investments,” FAO says.

Researchers used Collect Earth, part of the free, open source Open Foris software developed by FAO’s Forestry Department, to gather, analyze, report and share data obtained during the study.

Highlighting how advances in digital technology are spurring advances in ecosystems, climate and development research, FAO’s research team was able to carry out the global study in less than a year.

Summarizing some of the preliminary findings of its groundbreaking research FAO offers the following:


  • The global drylands contain 1.11 billion hectares of forest land, which is 27 percent of the global forest area, estimated at approximately 4 billion hectares.
  • Two-thirds of the drylands forest area can be defined as being dense, meaning it has closed canopies (i.e. a canopy cover greater than 40 percent).
  • The second most common land use in drylands is grassland (31 percent), followed by forest (18 percent) and cropland (14 percent). The category “other lands” constitutes 34 percent of the global drylands area.
  • The least-arid zones have the most forest. The proportion of forest land is 51 percent in the dry subhumid zone, 41 percent in the semiarid zone, 7 percent in the arid zone and 0.5 percent in the hyperarid zone. The average crown cover density is ten times higher in the dry subhumid zone than in the hyperarid zone.
  • Trees outside forests are present on 1.9 billion hectares of drylands (31 percent of the global drylands area), if all land with more than 0 percent crown cover is included. Thirty percent of croplands and grasslands have at least some crown cover, as do 60 percent of lands classified as settlements.

*Image credits: FAO

Andrew Burger
Andrew Burger
A product of the New York City public school system, Andrew Burger went on to study geology at the University of Colorado, Boulder, work in the wholesale money and capital markets for a major Japanese bank and earn an MBA in finance.

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