# Potential Global Sequestration of Atmospheric Carbon Dioxide by Semi-Arid Forestation

**Authors:** Rafat Qubaja, Murray Moinester, Joel Kronfeld  
**arXiv:** [2205.10641](https://arxiv.org/abs/2205.10641)  
**Date:** 2022-05-21  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2205.10641v3/

## Key points

- Study focused on carbon sequestration in the Yatir forest, a 28 km² Aleppo pine forest in Israel
- Organic carbon sequestration rate measured using Eddy Covariance flux and Carbon Stock counting methods: 550 grams of CO2 per square meter per year
- Estimated global organic sequestration rate after future global forestation: approximately 3.0 billion tons of CO2 per year (20% coverage of global semi-arid area)
- Inorganic carbon sequestration observed in Yatir forest through tree root exhalation of CO2, hydration by soil water, and precipitation of calcite
- Annual calcite precipitation rate measured at Yatir: 22 mg of CO2 per liter per year for sediment at a core depth of 2.2 meters
- Extrapolated estimate for global inorganic carbon sequestration: around 0.8 billion tons of CO2 per year assuming a global semi-arid average root respiration depth of 6 meters
- Total estimated carbon sequestration rate (organic + inorganic): approximately 4 billion tons of CO2 per year
- Highlights potential for carbon sequestration through widespread tree planting in semi-arid regions and emphasizes the need for further measurements and implementation of a global land management policy to reduce atmospheric CO2 levels

## Summary

The study focused on carbon sequestration in the Yatir forest, a 28 km² Aleppo pine forest located at the semi-arid timberline in Israel. The researchers measured the organic carbon sequestration rate (both above and below ground) using Eddy Covariance flux and Carbon Stock counting methods, and found it to be 550 grams of CO2 per square meter per year. Based on the representative soil composition at Yatir, they estimated a global organic sequestration rate of approximately 3.0 billion tons of CO2 per year after future global forestation, extrapolating to cover 20% of the global semi-arid area. The study also examined the inorganic carbon sequestration rate in the Yatir forest. It was observed that tree roots exhale CO2 into the soil, which is then hydrated by soil water to produce bicarbonate (HCO3-). This bicarbonate combines with soil calcium (Ca2+) to precipitate calcite (CaCO3). The researchers quantified this annual sequestration rate by measuring the decreased density of bicarbonates in the liquid phase of the soil unsaturated zone (USZ) in Yatir soil cores. They found that as calcite precipitates and incorporates within the USZ, the bicarbonate concentration decreases with depth. By converting depth profiles to time profiles and considering an annual downward water percolation rate of approximately 11 cm/yr at Yatir, they determined that the calcite precipitation rate was 22 mg of CO2 per liter per year for sediment at a core depth of 2.2 meters. Extrapolating these findings to a global scale and assuming a global semi-arid average root respiration depth of 6 meters, it is estimated that around 0.8 billion tons of CO2 could potentially be sequestered globally each year through inorganic carbon sequestration. When combined with the organic carbon sequestration rate, the total sequestration rate is estimated to be approximately 4 billion tons of CO2 per year. The study highlights the global potential for carbon sequestration through widespread tree planting in semi-arid regions and emphasizes the need for further measurements and implementation of a global land management policy to reduce atmospheric CO2 levels. This research provides valuable insights into forests' role in mitigating climate change by considering both organic and inorganic carbon sequestration mechanisms for future strategies.