Greening drylands despite warming consistent with carbon dioxide fertilization effect

Gonsamo, Alemu; Ciais, Philippe; Miralles, Diego G.; Sitch, Stephen; Dorigo, Wouter; Lombardozzi, Danica; Friedlingstein, Pierre; Nabel, Julia E. M. S.; Goll, Daniel S.; O’Sullivan, Michael; Arneth, Almut; Anthoni, Peter; Jain, Atul K.; Wiltshire, Andy; Peylin, Philippe; Cescatti, Alessandro

doi:10.1111/gcb.15658

Cited by 71 publications

(48 citation statements)

References 55 publications

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“…Moreover, global warming can enhance vegetation productivity by lengthening the active growing season and improving the maximum photosynthetic rate (Bastos et al., 2019; Myneni et al., 1997; Nemani et al., 2003; Thomas et al., 2016). The widespread increases in vegetation productivity driven by the warming and CO 2 fertilization effects have been observed across the globe (Gonsamo et al., 2021; Zhu et al., 2016). However, recent studies indicated that Earth is undergoing a sharp rise in atmospheric dryness as a result of the increased vapor pressure deficit (VPD) (Ficklin & Novick, 2017; Jung et al., 2010; Lopez et al., 2021; Yuan et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

Increased Global Vegetation Productivity Despite Rising Atmospheric Dryness Over the Last Two Decades

et al. 2022

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Rising atmospheric dryness [vapor pressure deficit (VPD)] can limit photosynthesis and thus reduce vegetation productivity. Meanwhile, plants can benefit from global warming and the fertilization effect of carbon dioxide (CO2). There are growing interests to study climate change impacts on terrestrial vegetation. However, global vegetation productivity responses to recent climate and CO2 trends remain to be fully understood. Here, we provide a comprehensive evaluation of the relative impacts of VPD, temperature, and atmospheric CO2 concentration on global vegetation productivity over the last two decades using a robust ensemble of solar‐induced chlorophyll fluorescence (SIF) and gross primary productivity (GPP) data. We document a significant increase in global vegetation productivity with rising VPD, temperature, and atmospheric CO2 concentration over this period. For global SIF (or GPP), the decrease due to rising VPD was comparable to the increase due to warming but far less than the increase due to elevated CO2 concentration. We found that rising VPD counteracted only a small proportion (approximately 8.1%–15.0%) of the warming and CO2‐induced increase in global SIF (or GPP). Despite the sharp rise in atmospheric dryness imposing a negative impact on plants, the warming and CO2 fertilization effects contributed to a persistent and widespread increase in vegetation productivity over the majority (approximately 66.5%–72.2%) of the globally vegetated areas. Overall, our findings provide a quantitative and comprehensive attribution of rising atmospheric dryness on global vegetation productivity under concurrent climate warming and CO2 increasing.

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Section: Introductionmentioning

confidence: 99%

Increased Global Vegetation Productivity Despite Rising Atmospheric Dryness Over the Last Two Decades

et al. 2022

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“…Land carbon stocks and fluxes, and thus the natural land sink, are affected by increases in atmospheric CO 2 as well as changes in nitrogen deposition, land use change (LUC) and the response of ecosystems to climate variability since the beginning of the industrial age. Elevated atmospheric CO 2 mixing ratios directly stimulate plant productivity through CO 2 fertilization and enhancements in plant water use efficiency in arid regions (Gonsamo et al., 2021; Schimel et al., 2015). These factors, combined with its contributions to warming at high latitudes, contribute to longer growing seasons.…”

Section: The Terrestrial Carbon Cyclementioning

confidence: 99%

How Well Do We Understand the Land‐Ocean‐Atmosphere Carbon Cycle?

Crisp

Dolman

Tanhua

et al. 2022

Reviews of Geophysics

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Fossil fuel combustion, land use change and other human activities have increased the atmospheric carbon dioxide (CO2) abundance by about 50% since the beginning of the industrial age. The atmospheric CO2 growth rates would have been much larger if natural sinks in the land biosphere and ocean had not removed over half of this anthropogenic CO2. As these CO2 emissions grew, uptake by the ocean increased in response to increases in atmospheric CO2 partial pressure (pCO2). On land, gross primary production also increased, but the dynamics of other key aspects of the land carbon cycle varied regionally. Over the past three decades, CO2 uptake by intact tropical humid forests declined, but these changes are offset by increased uptake across mid‐ and high‐latitudes. While there have been substantial improvements in our ability to study the carbon cycle, measurement and modeling gaps still limit our understanding of the processes driving its evolution. Continued ship‐based observations combined with expanded deployments of autonomous platforms are needed to quantify ocean‐atmosphere fluxes and interior ocean carbon storage on policy‐relevant spatial and temporal scales. There is also an urgent need for more comprehensive measurements of stocks, fluxes and atmospheric CO2 in humid tropical forests and across the Arctic and boreal regions, which are experiencing rapid change. Here, we review our understanding of the atmosphere, ocean, and land carbon cycles and their interactions, identify emerging measurement and modeling capabilities and gaps and the need for a sustainable, operational framework to ensure a scientific basis for carbon management.

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“…We excluded drylands >55 °north and south of the Equator to omit "cold" permafrost drylands, resulting in a global dryland area of 59.1 × 10 6 km 2 . While LSMs do not always simulate drylands exactly coincident with this climatic mask, this masking approach is standard (e.g., Ahlström et al, 2015;Yao et al, 2020;Gonsamo et al, 2021).…”

Section: Dryland Delineationmentioning

confidence: 99%

“…This is compounded by limitations in parameterisation data on land use and localised precipitation (Yang et al, 2020). This uncertainty is further exacerbated by a backdrop of changing environmental conditions including CO 2 fertilization, increasing plant water use efficiency, fire suppression, woody shrub encroachment, and increasingly variable precipitation, leaving considerable uncertainty around the resilience of dryland ecosystem function (Gonsamo et al, 2021;Maestre et al, 2021;Walker et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Assessing Model Predictions of Carbon Dynamics in Global Drylands

Fawcett

Cunliffe

Sitch

et al. 2022

Front. Environ. Sci.

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Drylands cover ca. 40% of the land surface and are hypothesised to play a major role in the global carbon cycle, controlling both long-term trends and interannual variation. These insights originate from land surface models (LSMs) that have not been extensively calibrated and evaluated for water-limited ecosystems. We need to learn more about dryland carbon dynamics, particularly as the transitory response and rapid turnover rates of semi-arid systems may limit their function as a carbon sink over multi-decadal scales. We quantified aboveground biomass carbon (AGC; inferred from SMOS L-band vegetation optical depth) and gross primary productivity (GPP; from PML-v2 inferred from MODIS observations) and tested their spatial and temporal correspondence with estimates from the TRENDY ensemble of LSMs. We found strong correspondence in GPP between LSMs and PML-v2 both in spatial patterns (Pearson’s r = 0.9 for TRENDY-mean) and in inter-annual variability, but not in trends. Conversely, for AGC we found lesser correspondence in space (Pearson’s r = 0.75 for TRENDY-mean, strong biases for individual models) and in the magnitude of inter-annual variability compared to satellite retrievals. These disagreements likely arise from limited representation of ecosystem responses to plant water availability, fire, and photodegradation that drive dryland carbon dynamics. We assessed inter-model agreement and drivers of long-term change in carbon stocks over centennial timescales. This analysis suggested that the simulated trend of increasing carbon stocks in drylands is in soils and primarily driven by increased productivity due to CO2 enrichment. However, there is limited empirical evidence of this 50-year sink in dryland soils. Our findings highlight important uncertainties in simulations of dryland ecosystems by current LSMs, suggesting a need for continued model refinements and for greater caution when interpreting LSM estimates with regards to current and future carbon dynamics in drylands and by extension the global carbon cycle.

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Greening drylands despite warming consistent with carbon dioxide fertilization effect

Cited by 71 publications

References 55 publications

Increased Global Vegetation Productivity Despite Rising Atmospheric Dryness Over the Last Two Decades

Increased Global Vegetation Productivity Despite Rising Atmospheric Dryness Over the Last Two Decades

How Well Do We Understand the Land‐Ocean‐Atmosphere Carbon Cycle?

Assessing Model Predictions of Carbon Dynamics in Global Drylands

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