Accelerated dryland expansion regulates future variability in dryland gross primary production

Jingyu Yao,Dan Li,Jianping Huang,Zhongming Gao,Guoyin Wang,Heping Liu,Xingyuan Chen,Haipeng Yu

doi:10.1038/s41467-020-15515-2

Abstract

Drylands cover 41% of Earth’s surface and are the largest source of interannual variability in the global carbon sink. Drylands are projected to experience accelerated expansion over the next century, but the implications of this expansion on variability in gross primary production (GPP) remain elusive. Here we show that by 2100 total dryland GPP will increase by 12 ± 3% relative to the 2000–2014 baseline. Because drylands will largely expand into formerly productive ecosystems, this increase in dryland GPP may not increase global GPP. Further, GPP per unit dryland area will decrease as degradation of historical drylands outpaces the higher GPP of expanded drylands. Dryland expansion and climate-induced conversions among sub-humid, semi-arid, arid, and hyper-arid subtypes will lead to substantial changes in regional and subtype contributions to global dryland GPP variability. Our results highlight the vulnerability of dryland subtypes to more frequent and severe climate extremes and suggest that regional variations will require different mitigation strategies.

Highlights

Drylands cover 41% of Earth’s surface and are the largest source of interannual variability in the global carbon sink
The largest positive contributions to the increased dryland gross primary production (GPP) trend occurred in North America (45%), East Asia (21%), and Africa/ Australia (18%) (Figs. 1c and 2; Supplementary Table 2), whereas the largest contributions to the global dryland interannual variability (IAV) occurred in Australia (25%), South America (20%), and Africa (15%) (Fig. 1d and Supplementary Table 3)
The remaining 18% of the dryland GPP variability was explained by a combination of other drivers including soil moisture, vapor pressure deficit (VPD), and potential evapotranspiration (PET) (“Methods”; Supplementary Figs. 2 and 3)

Summary

Introduction

Drylands cover 41% of Earth’s surface and are the largest source of interannual variability in the global carbon sink. Global dryland ecosystems with high biomass turnover rates have accounted for ~40% of the global land net primary production (NPP), dominated the positive global land CO2 sink trend, and contributed the largest fractions to the interannual variability (IAV) of net CO2 flux over recent decades[9,10,11,12]. Such carbon sink variability has been mostly associated with variations in gross primary production (GPP). Model projections show that drylands will experience an accelerated expansion of 11 and 23% by the end of the 21st century under the Representative Concentration Pathway 4.5

Methods

Results

Conclusion