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Carbon Cycling in Global Drylands

Lal, Rattan
Current climate change reports 2019 v.5 no.3 pp. 221-232
arid lands, arid zones, biomass, carbon dioxide, carbon sequestration, carbon sinks, climate change, desertification, ecosystems, groundwater, inorganic carbon, land degradation, net primary productivity, risk, soil, soil erosion, water shortages
PURPOSE OF REVIEW: The aim of this paper is to describe the carbon cycle in drylands in relation to the processes, factors, and causes affecting it. A specific focus is placed on both biotic and abiotic mechanisms of carbon sequestration in drylands in relation to mitigation of the anthropogenic climate change. RECENT FINDINGS: Global dryland area is increasing along with an increase in risks of desertification, salinization, and eolian/hydrologic processes of accelerated soil erosion with strong impacts on the carbon cycle. Nonetheless, drylands contribute strongly towards the land-based sink of the atmospheric carbon dioxide through sequestration of carbon in the soil, ground water, and biomass. Thus, dryland ecosystems affect inter-annual variability in the global carbon cycle and create a negative feedback through carbon sequestration. Global drylands, covering 66.7 M km² or 45.36% of the Earth’s land area, strongly impact the ecosystem carbon stock, contribute to the land-based carbon sink, and provide a negative feedback to the global carbon cycle. Whereas the net primary productivity is limited by the water scarcity, especially in hyper-arid and arid ecoregions, sequestration of inorganic carbon in soil and ground water is an important control of the carbon cycle. Desertification, caused by eolian and hydrologic erosion along with salinization, must be controlled and reversed to enhance carbon sequestration, achieve land degradation neutrality, and create a negative feedback. Carbon sequestration strategy recognizes “soil” as a rights holder to be protected, restored and naturally evolve.