Climate mitigation potential of natural climate solutions and clean energy on The Nature Conservancy properties in California, USA

Clean energy solutions on The Nature Conservancy’s fee-owned lands contributed mod- estly to CO2e reduction compared to NCS. While we accounted for the electricity and fossil fuel emissions from buildings and water pumps on the properties, this is not a complete accounting of the chapter’s carbon footprint. Most of the carbon emissions pre-Covid pan- demic were due to air travel by staff and transportation to and from offices (unpublished data). Reducing these indirect emissions will be key to mitigating The Nature Conservancy’s carbon footprint. Adopting a portfolio of different NCS activities and clean energy solutions is likely they best past forward for The Nature Conservancy to mitigate climate change and follows the state’s carbon neutrality plan [10] and recommendations to focus on both NCS and clean energy to mitigate climate change [38]. The Nature Conservancy, California chapter is not the only organization setting ambitious CO2e reduction goals based on the implementation of NCS and clean energy. Other state and country chapters of The Nature Conservancy have set reduction goals that combined add up to 3 GTCO2e year –1 (3 billion metric tons) by 2030. Conservation International set a goal of avoiding 2 GTCO2e year –1 by conserving carbon rich ecosystems, specifically peat, man- groves, and old-growth forests. U.S. Agency for International Development’s (USAID) goal is 6 GTCO2e year –1 by conserving, restoring, and managing 100 M ha and implementing clean energy. The combined reduction goal of these three organizations is 11 GTCO2e year –1,

almost half the estimated global potential of NCS [2]. While ambitious goals are needed to hold the increase in average temperature to 2˚ C over pre-industrial levels per the Paris Agreement, adoption and implementation may be slower than hoped for. This may be due to landowners’ acceptance of different NCS activities or need- ing to balance tradeoffs with other land uses such as biodiversity conservation and food pro- duction as discussed in this study. Adoption may also be slow because carbon market payments are too low, NCS do not qualify for payments, or there are questions about the long- term security of the funding [39]. There is also a time-lag to implement NCS due to planning and permitting requirements for restoration or delayed CO2e reduction impact post-restora- tion [6]. The Nature Conservancy and other large private landowners are in a unique position to implement a diverse NCS and clean energy portfolio, document the co-benefits and trade- offs, and inspire more widespread adoption by other private landowners. Limitations in this study include not accounting for the costs, incomplete accounting of indirect emissions, and not incorporating the risk of loss. Costs could be incorporated into a future study to guide The Nature Conservancy’s investments in NCS solutions that have the greatest return on investment. Future studies could also consider indirect emissions from cat- tle grazing, fertilizer application, fuel powered vehicles, and other activities by lessees or prop-

erty owners on the properties. There is also the issue of permanence in climate mitigation from NCS that may be at risk from climate change and increases in wildfire and drought reversing the reduction. Incorporating risk of loss under climate change into the analysis of reduction could inform where to prioritize NCS activities with the greatest likelihood of suc- cess now and in the future under climate change. Conclusions This study demonstrates how CO2e reduction from NCS and clean energy transitions can be assessed for an individual large landowner. We show how the potential CO2e reduction from future implementation of restoration, changes to agricultural management, and switching to clean energy on fee-owned properties in California will not reach the chapter’s 2030 CO2e goal. PLOS ONE Climate mitigation potential of natural climate solutions and clean energy: The nature conservancy, California PLOS ONE | https://doi.org/10.1371/journal.pone.0311195 October 21, 2024 11 / 14