A framework for integrating the terrestrial carbon stock of estates in institutional carbon management plans

Abstract

Many institutions have substantial landholdings, but few consider soil carbon preservation and augmentation in their carbon management plans. A methodical framework was developed to analyse terrestrial carbon stocks (soil and tree biomass) for credible carbon offsetting strategies in institutional land. This approach was demonstrated at two farms (805 hectares) managed by Newcastle University. Soil carbon for three depths (0–30 cm, 30–60 cm and 60–90 cm) and above‐ground tree biomass were quantified. These data provided a terrestrial carbon baseline to evaluate future land management options and effects. Historical land‐use records enabled the following comparisons: (1) agricultural land vs. woodland; (2) arable land vs. permanent grassland; (3) organic vs. conventional farming; (4) coniferous vs. broadleaved woodland; and (5) recent vs. long‐established woodland. Carbon storage (kg/m2) varied with land usage and woodland type and age, but only agricultural land vs. woodland, and for agriculture, arable land vs. permanent grassland, significantly affected the 0–90 cm soil carbon. At the university‐managed farms, current terrestrial carbon stocks were 103,620 tonnes in total (98,050 tonnes from the 0–90 cm soil and 5,569 tonnes from tree biomass). These terrestrial carbon stocks were equivalent to sixteen years of the current carbon emissions of Newcastle University (6,406 tonnes CO2 equivalents‐C per year). Using strategies for alternative land management, Newcastle University could over 40 years offset up to 3,221 tonnes of carbon per year, or 50% of its carbon emissions at the current rate. The methodological framework developed in this study will enable institutions having large landholdings to rationally consider their estates in future soil carbon management schemes.

The limited potential of soil and vegetation in urban greenspace for nature‐based offsetting of institutional carbon emissions

“…The limits to what can be achieved with nature‐based carbon offsetting in urban greenspace also emphasize the need to substantially reduce emissions when building a green city, such as switching to renewable energy systems, popularizing low‐carbon transport infrastructures (Newcastle City Council, 2020), deploying eco‐homes (Pickerill, 2017), eco‐driving and eco‐charging (Ortega‐Cabezas et al., 2021). Importantly, the limited ability of urban soil management to accommodate carbon emphasizes the need for urban centres to work with rural partners, where soil carbon management achieves much higher gains in stocks (Wang et al., 2021).…”

“…According to IPCC (2006), the best practices for carbon accounting because of land‐use change or management will require soil sampling of the top 0.3 m depth. Therefore, the top 0–30 cm of the soil profile was sampled as most organic carbon accumulates in this interval of the soil profile (Wang et al., 2021) and to avoid services (pipes and cables) that could have been damaged by deeper sampling. Previous research recommended that 30–50 soil sampling points should provide a reliable representation of soil carbon for different land covers (Edmondson et al., 2014).…”

“…However, the university currently does not know or actively manage the carbon stored in the soils and trees of its urban campus as part of its carbon management plan. There is a growing body of research to address the task of carbon reduction with investigations of land management and soil carbon storage across agricultural lands and woodlands over two farms owned by the same institution (Wang et al, 2021;Zani et al, 2023). The farms owned by Newcastle University could be a strong terrestrial carbon sink, where the land alteration scheme with the best performance for net-zero could achieve a 50% removal of institutional carbon emission in 2019 (Wang et al, 2021).…”

Diversified crop rotations and organic amendments as strategies for increasing soil carbon storage and stabilisation in UK arable systems

“…The soil mineralogical composition across the farm is predominantly composed of quartz, with 1:1 clay minerals (kaolinite) and minor illite, and alkali feldspar, particularly in subsoil layers (>0.30 m) (Supplementary Table S1). Coal fragments, derived from till via glacial erosion of Carboniferous rocks, occurs in the soil, but insufficiently to confound measurement of non-geological SOC (Wang et al, 2022).…”

Soil health and ecosystem services

“…Soil carbon management can also play a role for large landholding institutions to reach carbon zero goals. For instance, a recent study found that Newcastle University in the United Kingdom can off-set 50% of its current emission over a 40-year period by using alternative land management strategies (Wang, Werner, & Manning, 2022).…”