Soil resources and element stocks in drylands to face global issues

Drylands (hyperarid, arid, semiarid, and dry subhumid ecosystems) cover almost half of Earth’s land
surface and are highly vulnerable to environmental pressures. Here we provide an inventory of soil
properties including carbon (C), nitrogen (N), and phosphorus (P) stocks within the current boundaries
of drylands, aimed at serving as a benchmark in the face of future challenges including increased
population, food security, desertification, and climate change. Aridity limits plant production and
results in poorly developed soils, with coarse texture, low C:N and C:P, scarce organic matter, and high
vulnerability to erosion. Dryland soils store 646 Pg of organic C to 2 m, the equivalent of 32% of the
global soil organic C pool. The magnitude of the historic loss of C from dryland soils due to human land
use and cover change and their typically low C:N and C:P suggest high potential to build up soil organic
matter, but coarse soil textures may limit protection and stabilization processes. Restoring, preserving,
and increasing soil organic matter in drylands may help slow down rising levels of atmospheric carbon
dioxide by sequestering C, and is strongly needed to enhance food security and reduce the risk of land
degradation and desertification.