An underappreciated climate change risk
Land-based nature-based solutions (NbS) could deliver ~11.8 Gt CO2e per year of cost-effective carbon mitigation, according to a recent report by Climate Focus and the Food and Land Use Coalition (FOLU). This chimes with the conclusions of other academic estimates that suggest that 8-14 Gt CO2e could be mitigated per year.1
However, academic studies rarely consider what’s realistic in practice.
There are significant barriers in the way of broader adoption, including political, economic, social, spatial, and legal factors. Based on these constraints Climate Focus/FOLU estimate that land-based NbS has a realistic mitigation potential of 2-3.6 Gt CO2e per year by 2030, rising to 3.2-5.1 Gt CO2e per year by 2050.
Overall, based on this analysis at least, NbS could realistically deliver ~12% of the mitigation needed by 2030 to be on course for 1.5°C by 2050.2
Climate Focus/FOLU analysis suggests that improved agricultural practices have the potential to deliver the bulk of the mitigation (43%, 1.15 Gt CO2e). Avoided deforestation, the dominant NbS category today, is next (32%, 0.86 Gt CO2e), followed by afforestation/reforestation (11%, 0.28 Gt CO2e), improved forest management (7%, 0.19 Gt CO2e), and the restoration and conservation of wetlands (7%, 0.19 Gt CO2e).
Carbon sequestration via agriculture only really makes sense when there are dramatic economies of scale to exploit. The cost involved with project development, testing, monitoring and then introducing technology to improve the management of the land, not to mention the long timescales involved, mean that only the largest farms can currently exploit and take advantage. It’s for this reason that the practice is only really gaining traction in the United States and Australia (see Carbon farming puts a value on dirt: Soil carbon sequestration is the next frontier of the carbon market).
Are the NbS mitigation estimates realistically going to be achieved over the rest of the decade?
It’s an important question to answer for corporations and governments looking to NbS to meet voluntary carbon targets, and national and global compliance requirements. Any delay in implementation means that current and prospective buyers of nature based carbon credits will need to revise down their expectations of the potential for Gt CO2e mitigated.
There are two constraints that most analysis into NbS supply fails to consider.
The first constraint is time. It takes time to choose the right project location, and engage with local stakeholders. It takes time to develop the methodology and ensure that the processes are in place to ensure carbon credits can be generated. It takes time to ensure that the project is validated, has been verified, and monitoring processes are in place. Overall, it typically takes between 1 and 3 years to implement a NbS project, depending on the complexity of the project and the jurisdiction in which it is operating in.
The second constraint is the same phenomenon that NbS carbon projects are looking to solve - climate change. A warmer world is poised to exacerbate the wildfires, insect outbreaks, and drought conditions that already threaten many forests and other natural habitats. Hotter conditions and a drier atmosphere will reduce the amount of CO2 sequestered, while also increasing the risk that greenhouse gases (GHG) are subsequently released into the atmosphere.
We’re only beginning to understand the risks involved.
Frequent periods of drought and extreme heat have been shown to reduce the amount of carbon sequestered by tropical forests. Research carried out in the South America during 2015-16 (at the time the region was suffering from drought and record temperatures) showed tropical forests lost their ability to function as a carbon sink. That was a surprise as up until recently, tropical forests have been thought to be relatively resilient to extreme climatic conditions.3
Carbonplan, the environmental non-profit organisation, recently analysed the historical relationship between climate conditions in the US during 1984–2018, and the risk of fire and other measures of climate risk (e.g., drought, insects, etc.). The researchers found that fire risk could rise by a factor of four during the 21st century, while climate-stress mortality risk could increase by 30%.4
The impact of climate change suggests that NbS supply will become significantly more constrained, increasing the time necessary to deliver the Gt CO2e we need to meet net zero targets. A sensible strategy is for buyers of nature-based carbon credits to take a portfolio approach to managing climate risk. This means allocating across a range of NbS types, and potentially securing a larger proportion of credit needs sooner, rather than later. Bear in mind though that as with any market where the supply is heavily constrained (and set to get even tighter), you only need a small increase in demand for prices to move significantly higher.
Most academic studies into carbon sequestration estimate the carbon abatement potential of land-based NbS to be in the range of 8 to 14 Gt CO2e per year. The Intergovernmental Panel on Climate Change (IPCC) has suggested that 19 Gt CO2e per year is the maximum. Even this number seems way too high. To sequester that much carbon every year would require 1 billion hectares of land. To put that in comparison, the total land area currently devoted to growing crops is 1.5 billion hectares. Some estimates put the theoretical maximum Gt sequestered at even higher levels.
https://climatefocus.com/wp-content/uploads/2022/12/Global-analysis-of-available-supply-potential.pdf
https://www.nature.com/articles/s41558-023-01776-4
https://www.nature.com/articles/s41561-023-01322-z?hss_channel=lcp-54117489