Preventing, halting and reversing the degradation of forest ecosystems in the drylands.
Desert Leaves’ mission is to increase and disseminate knowledge about forests and forestation in dryland regions, to connect and support people and organizations around the globe that are involved in dryland afforestation and forest preservation, and thus to support initiatives that pursuit the growth of sustainable forests in drylands.
Sheil, D., & Bargués-Tobella, A. (2020). More trees for more water in drylands: myths and opportunities. ETFRN News.
The restoration of tree cover influences water availability. Many people—some experts too—believe incorrectly that greater tree cover has an invariably negative impact on local water availability. Where do these beliefs come from? Here we summarise the origin of these misconceptions and illustrate how tree cover can improve water availability. We have recognised the extent of these opportunities only recently, and considerable work remains, but we know enough to dismiss some myths and to highlight major opportunities to improve water security in Africa by restoring degraded landscapes with trees.
Del Campo, A. D., González-Sanchis, M., Ilstedt, U., Bargués-Tobella, A., & Ferraz, S. (2019). Dryland forests and agrosilvopastoral systems: water at the core. Unasylva 251: Forests: nature-based solutions for water, 251(1), 27.
Dryland systems occur on all continents and cover about 41 percent of the Earth’s land surface, with little variation in this figure in recent decades (Cherlet et al., 2018). Drylands differ in their moisture deficit and can be classified in four subtypes according to the United Nations Environment (UNEP) aridity index (AI)1 as dry subhumid (0.65– 0.5), semiarid (0.5–0.2), arid (0.2–0.05) or hyperarid (<0.05) (Figure 1).2 Forests and grasslands are the dominant biomes in the dry subhumid and semiarid subtypes, respectively (more than 60 percent of the subtype areas). On the other hand, the arid and hyperarid subtypes are mostly treeless (FAO, 2016) and thus beyond the scope of this article.
Based on their underlying definition (i.e. by AI), annual potential evapotranspiration (PET) in dry subhumid and semiarid lands is considerably higher than annual precipitation, with frequent meteorological droughts. These atmospheric drivers lead to low soil moisture and this, in turn, means slow tree growth and low productivity, resulting in a socio-ecological context of water scarcity. Marked rainfall seasonality, with torrential events followed by long dry periods, and the combination of high intra- and interannual variability, put such regions within the “difficult” hydrology framework, which hampers water security, sustainable development and poverty reduction (Grey and Sadoff, 2007). southern Africa, Australia, the Middle East and Central Asia (Cherlet et al., 2018). The intensification of precipitation and other climatic extremes under warmer conditions is likely to increase water scarcity and moisture deficits in drylands and beyond. Climatic constraints increase the role of soil processes and properties in the regulation and magnitude of water-related issues in drylands, especially those concerned with resource storage (e.g. soil depth, infiltrability, deep-water storage and erosion). Thus, land-use and management practices, especially nature-based solutions, are extremely important for the soil–water–productivity complex. This article uses case studies in dryland on three continents to show the importance of a water-centred approach to dryland management for increasing resilience and adaptation to climate change
Bastin, J. F., Finegold, Y., Garcia, C., Mollicone, D., Rezende, M., Routh, D., … & Crowther, T. W. (2019). The global tree restoration potential. Science, 365(6448), 76-79.
Climate change is expected to cause an increase in the global area of drylands of 10–23 percent, depending on dryland subtype, by the end of the twenty-first century, particularly in areas of North and South America, the Mediterranean,The restoration of trees remains among the most effective strategies for climate change mitigation.We mapped the global potential tree coverage to show that 4.4 billion hectares of canopy cover could exist under the current climate. Excluding existing trees and agricultural and urban areas, we found that there is room for an extra 0.9 billion hectares of canopy cover, which could store 205 gigatonnes of carbon in areas that would naturally support woodlands and forests. This highlights global tree restoration as our most effective climate change solution to date. However, climate change will alter this potential tree coverage.We estimate that if we cannot deviate from the current trajectory, the global potential canopy cover may shrink by ~223 million hectares by 2050, with the vast majority of losses occurring in the tropics. Our results highlight the opportunity of climate change mitigation through global tree restoration but also the urgent need for action.