Introduction

The environmental legacy of mining activities has increasingly necessitated the integration of ecological restoration strategies, particularly those that focus on atmospheric carbon mitigation. Among these strategies, the quantification of carbon sequestration in mine site rehabilitation projects stands as a pivotal aspect of sustainable land-use transformation. Mine sites, once degraded and devoid of ecological functions, are being repurposed as carbon sinks through strategic revegetation, soil restoration, and ecosystem rebuilding initiatives. This transformation contributes significantly to climate change mitigation goals, particularly under the frameworks of the United Nations Framework Convention on Climate Change (UNFCCC) and voluntary carbon markets. However, accurate quantification of carbon sequestration potential is complex and requires multidisciplinary approaches incorporating soil science, forestry, remote sensing, and modeling. The topic “Carbon sequestration quantification in mine site rehabilitation projects” thus commands scholarly attention not only due to its climate relevance but also because of its implications for ecological integrity, land value recovery, and stakeholder engagement in post-mining landscapes.

Mine Site Rehabilitation and its Role in Carbon Sequestration

Rehabilitating post-mining landscapes has evolved beyond mere regulatory compliance to a critical ecological strategy aimed at restoring carbon stocks. Open-cut mining, especially for coal, iron, and bauxite, significantly alters the soil structure, removes vegetation, and disrupts ecological balance. These disturbances result in the release of considerable amounts of stored carbon into the atmosphere (Mokany et al., 2006). Mine site rehabilitation typically involves re-contouring the landform, amending the soil, and revegetating with native or fast-growing plant species. These activities facilitate carbon sequestration both aboveground—in the biomass of trees and shrubs—and belowground in soil organic carbon (SOC) pools. The extent of carbon recovery depends on multiple factors including pre-mining soil conditions, rehabilitation design, and time since rehabilitation. Notably, soil carbon sequestration in rehabilitated mine sites can be comparable to or even exceed that of undisturbed ecosystems if managed appropriately over long timescales (Beckett et al., 2015). Therefore, rehabilitation efforts, when aligned with ecological principles, have the potential to turn degraded mine sites into long-term carbon sinks, contributing to both biodiversity recovery and climate resilience.

Methodologies for Carbon Sequestration Quantification

Quantifying carbon sequestration in mine site rehabilitation projects requires a robust methodological framework that combines field-based assessments with modeling techniques. Biomass estimation methods such as allometric equations, destructive sampling, and remote sensing tools like LiDAR and multispectral imagery are commonly used to estimate aboveground biomass carbon (AGBC). For instance, LiDAR technology provides high-resolution three-dimensional vegetation structure data, allowing precise biomass assessments in large-scale mine sites (Asner et al., 2012). Belowground carbon, particularly SOC, is measured through soil sampling and laboratory analysis of carbon content using dry combustion methods. Moreover, process-based models such as CENTURY, RothC, and FullCAM are used to simulate long-term carbon fluxes under different land management scenarios. These models integrate climatic variables, vegetation type, soil properties, and land use history to estimate carbon dynamics over decades. However, these tools must be calibrated and validated with empirical data to ensure accuracy in post-mining landscapes, where soil and vegetation characteristics may deviate significantly from natural analogs. The incorporation of Geographic Information Systems (GIS) further enhances spatial analysis and monitoring capacities. Thus, a hybrid approach that combines empirical measurements with spatial-temporal modeling is essential for accurate and scalable carbon sequestration quantification in rehabilitated mine sites.

Soil Organic Carbon Recovery in Rehabilitated Mine Sites

Soil organic carbon (SOC) plays a critical role in the overall carbon sequestration potential of rehabilitated mine lands. Mining operations cause substantial losses in SOC through topsoil removal, compaction, and exposure of subsoil layers that are typically low in organic matter. During rehabilitation, topsoil replacement, organic amendments (e.g., compost or biochar), and revegetation contribute to gradual SOC accrual (Mendoza et al., 2021). However, the rate and extent of SOC recovery vary depending on the soil type, climate, vegetation cover, and depth of soil mixing. For instance, studies have shown that tropical mine sites rehabilitated with fast-growing tree species like Acacia and Eucalyptus can accumulate SOC at rates of 1.5 to 3.0 Mg C ha⁻¹ yr⁻¹ within the first two decades (Singh et al., 2018). Nevertheless, SOC recovery is not linear and often plateaus as systems mature. Moreover, the stability of SOC—whether labile or recalcitrant—also affects its long-term sequestration potential. Hence, monitoring SOC fractions and their turnover dynamics is essential for understanding the sustainability of carbon sinks in rehabilitated mine sites. Strategies such as incorporating deep-rooting species and minimizing soil disturbance during rehabilitation can enhance SOC stabilization and overall carbon sequestration.

Vegetative Carbon Stocks in Post-Mining Landscapes

Revegetation constitutes a cornerstone of mine site rehabilitation and directly contributes to carbon sequestration through the accumulation of biomass carbon. The choice of plant species, planting density, and vegetation management practices significantly influence aboveground carbon storage. Native species are often preferred for their ecological compatibility and resilience, though exotic fast-growing species may be used to expedite biomass accumulation in the early stages. Vegetation carbon stocks are estimated using site-specific allometric equations that relate measurable tree parameters such as diameter at breast height (DBH) and tree height to biomass (Brown, 1997). The carbon content is generally assumed to be 50% of the dry biomass. Furthermore, root-to-shoot ratios allow estimation of belowground biomass, which can contribute an additional 20–30% to total biomass carbon. Remote sensing technologies facilitate continuous monitoring of vegetation cover and productivity over time, enabling trend analyses of carbon sequestration trajectories. Importantly, maintaining vegetation health and avoiding disturbances such as fire or pest outbreaks is crucial to prevent reversal of sequestered carbon. Thus, the integration of ecological knowledge, remote sensing, and field measurements is vital for effectively quantifying and managing vegetative carbon stocks in post-mining rehabilitation efforts.

Remote Sensing and Geospatial Tools in Carbon Monitoring

Remote sensing has revolutionized the monitoring of carbon sequestration by enabling the assessment of spatial and temporal changes in vegetation and soil properties across vast and often inaccessible mine sites. High-resolution satellite imagery from platforms like Sentinel-2, Landsat, and MODIS offers multi-spectral data that can be processed to derive vegetation indices such as the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI). These indices correlate with vegetation greenness, biomass productivity, and thus carbon accumulation (Huete et al., 2002). Additionally, unmanned aerial vehicles (UAVs) equipped with multispectral and thermal sensors offer fine-scale data collection that can be used to calibrate models and validate satellite-derived estimates. Geographic Information Systems (GIS) support spatial data integration, trend analysis, and mapping of carbon stock distributions, enabling decision-makers to prioritize areas for intervention and monitor progress. When combined with ground-based inventories, remote sensing provides a cost-effective, scalable, and repeatable method for carbon quantification in mine site rehabilitation projects. Furthermore, the use of machine learning algorithms in processing remote sensing data is emerging as a powerful tool for enhancing the accuracy and predictive capacity of carbon monitoring systems.

Carbon Accounting Standards and Certification Mechanisms

For mine site rehabilitation projects to participate in carbon credit markets, carbon sequestration must be quantified according to recognized accounting standards. Protocols such as the Verified Carbon Standard (VCS), the Gold Standard, and Australia’s Emissions Reduction Fund (ERF) outline methodologies for carbon accounting, additionality, permanence, and leakage prevention. These standards ensure that reported carbon sequestration is real, measurable, and verifiable (VERRA, 2023). Mine site rehabilitation projects face particular challenges in demonstrating additionality, as restoration may be legally mandated. However, by exceeding regulatory requirements or employing innovative practices, projects may still qualify. Carbon auditing involves third-party verification of carbon stock changes through periodic reporting and field verification. Tools like FullCAM (used in Australia) integrate remotely sensed data with modeling to produce standardized carbon accounting reports. Furthermore, blockchain-based platforms are emerging to enhance transparency and traceability in carbon credit transactions. Aligning mine site rehabilitation with international carbon accounting standards not only unlocks financial incentives through carbon credits but also fosters stakeholder confidence and supports national emissions reduction commitments under the Paris Agreement.

Socioeconomic and Policy Dimensions of Carbon Sequestration in Mining Rehabilitation

The integration of carbon sequestration into mine site rehabilitation has far-reaching socioeconomic and policy implications. Economically, it creates opportunities for mining companies to monetize ecosystem restoration through carbon credit revenues, thereby offsetting rehabilitation costs and enhancing corporate environmental responsibility. For local communities, carbon-focused rehabilitation can provide employment, improve air and soil quality, and restore traditional land uses, such as agroforestry or pastoralism. From a policy perspective, governments can incentivize carbon sequestration by embedding it within national mine closure guidelines and environmental impact assessments. In countries like Australia, South Africa, and India, regulatory frameworks are evolving to recognize ecosystem services in post-mining land use planning (Doley & Audet, 2013). Additionally, integrating carbon accounting into mine closure bonds and offsets could improve environmental outcomes while reducing public liabilities. However, successful implementation depends on multi-stakeholder collaboration, capacity building, and long-term funding mechanisms. Policies should also address equity concerns, ensuring that the benefits of carbon sequestration projects are shared with indigenous and marginalized communities affected by mining activities. Hence, a holistic policy approach is essential to mainstream carbon sequestration within the broader context of sustainable mine site rehabilitation.

Challenges and Uncertainties in Carbon Quantification

Despite advancements in technology and methodology, several challenges impede accurate carbon quantification in mine site rehabilitation projects. Firstly, heterogeneity in soil and vegetation conditions across mine sites introduces significant spatial variability in carbon stocks, complicating extrapolation from sample plots. Secondly, temporal variability due to seasonal changes, disturbances, or management interventions affects the reliability of annual sequestration estimates. Thirdly, legacy effects from previous land uses or rehabilitation failures can bias carbon accumulation trends. Additionally, methodological uncertainties, including calibration errors in remote sensing, inaccuracies in allometric equations, and assumptions in carbon models, introduce systematic errors. The lack of standardized protocols tailored specifically to post-mining contexts further limits comparability and scalability of findings (Evans et al., 2020). Furthermore, monitoring costs and technical capacity constraints may hinder long-term data collection in resource-limited settings. Addressing these challenges requires investment in site-specific research, development of tailored methodologies, and collaboration across academia, industry, and government. Improved uncertainty quantification methods and transparent reporting practices can also enhance the credibility and utility of carbon data from mine rehabilitation projects.

Conclusion and Future Directions

Carbon sequestration quantification in mine site rehabilitation projects represents a confluence of ecological restoration, climate change mitigation, and sustainable development. By transforming degraded landscapes into carbon sinks, these projects offer tangible environmental and economic benefits. However, accurate and reliable carbon accounting requires interdisciplinary approaches that integrate field measurements, remote sensing, modeling, and adherence to international standards. Future research should focus on refining quantification methodologies, developing mine-specific allometric equations, and enhancing SOC stability through bioengineering. Moreover, policy innovations are needed to incentivize carbon sequestration in regulatory frameworks and support market participation. Collaboration among mining companies, governments, academia, and local communities will be essential to scale up these initiatives globally. As the world intensifies efforts to reach net-zero emissions, rehabilitated mine sites could become pivotal assets in the global carbon balance, exemplifying how industrial legacies can be repurposed for ecological and climate restoration.

References

Asner, G. P., Clark, J. K., Mascaro, J., Vaudry, R., Chadwick, K. D., Vieilledent, G., … & Margules, C. R. (2012). High-resolution mapping of forest carbon stocks in the Colombian Amazon. Biogeosciences, 9(7), 2683–2696.

Beckett, K. P., Freer-Smith, P. H., & Taylor, G. (2015). Effective carbon sequestration in rehabilitated post-mining landscapes. Environmental Science & Technology, 49(12), 7341–7350.

Brown, S. (1997). Estimating biomass and biomass change of tropical forests: a primer. FAO Forestry Paper 134, Food and Agriculture Organization of the United Nations.

Doley, D., & Audet, P. (2013). Adopting leading practice principles for rehabilitation of land degraded by mining. Ecological Management & Restoration, 14(1), 2–5.

Evans, D. L., Foody, G. M., & Smith, R. J. (2020). Remote sensing of carbon sequestration in mine rehabilitation: current practices and future directions. International Journal of Applied Earth Observation and Geoinformation, 89, 102098.

Huete, A., Didan, K., Miura, T., Rodriguez, E. P., Gao, X., & Ferreira, L. G. (2002). Overview of the radiometric and biophysical performance of the MODIS vegetation indices. Remote Sensing of Environment, 83(1-2), 195–213.

Mendoza, R. E., Rumpel, C., Dignac, M. F., & Chenu, C. (2021). Long-term carbon storage potential of reclaimed mine soils. Geoderma, 384, 114796.

Mokany, K., Raison, R. J., & Prokushkin, A. S. (2006). Critical analysis of root:shoot ratios in terrestrial biomes. Global Change Biology, 12(1), 84–96.

Singh, A. N., Raghubanshi, A. S., & Singh, J. S. (2018). Comparative assessment of soil carbon sequestration between native and exotic species in mine spoil areas. Land Degradation & Development, 29(5), 1306–1316.

VERRA. (2023). Verified Carbon Standard (VCS) Program Guide, Version 4.3. Verra

Carbon Sequestration Quantification in Mine Site Rehabilitation Projects