The carbon security index: A novel approach to assessing how secure carbon is in sagebrush ecosystems within the Great Basin

Authors: O'Connor, Rory; Boyd, Chad; NAUGLE, DAVE - University Of Montana; SMITH, JOSEPH - University Of Montana

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2024
Publication Date: 10/15/2024
Citation: O'Connor, R.C., Boyd, C.S., Naugle, D.E., Smith, J.T. 2024. The carbon security index: A novel approach to assessing how secure carbon is in sagebrush ecosystems within the Great Basin. Rangeland Ecology and Management. 97:169-177. https://doi.org/10.1016/j.rama.2024.08.005.
DOI: https://doi.org/10.1016/j.rama.2024.08.005

Interpretive Summary: Rangeland carbon is often conceptualized as being like intensively managed agricultural lands, in that we need to sequester and store more carbon. However, unlike intensively managed agricultural lands that become homogenous, rangelands are complex and diverse landscapes where soils and plant communities can change in sort distances, thus changing the carbon dynamics. To manage rangeland carbon, we need a new paradigm that focuses on maintaining and securing carbon from disturbances, like fire, and conversions (e.g., annual grasslands and conifer woodlands). Carbon security is the likelihood of carbon being protected and stored over time at a location. We developed the Carbon Security Index (CSI) to monitor changes in carbon security across the Great Basin from 1989 to the present year. We found that the Great Basin has decreased carbon security by 53% over the last 30 years in part because of wildfire disturbance and conversions from native sagebrush rangeland to annual grasslands and conifer woodlands. To help land managers manage carbon we adapted CSI into a management map to easily identify areas of high carbon security so that it can be protected. To manage rangeland carbon effectively we need to think about maintaining the carbon we have and secure that carbon so it is not lost.

Technical Abstract: Rangeland carbon is often conceptualized similarly to intensively managed agricultural lands, in that we need to sequester and store more carbon. Unlike intensively managed agricultural lands, rangeland soils cannot sequester more carbon due to pedogenic and climatic limitations that influence plant community and microbial community dynamics. This requires a new paradigm for rangeland carbon that focuses on maintaining carbon security following disturbances like fire and plant community conversions (e.g., annual grasslands and conifer woodlands). To attain this, we propose the creation of a Carbon Security Index (CSI). CSI is a unitless, scalable value that can be used to compare carbon security across range- land sites and over time and incorporates a plant fractional cover ratio, resistance and resilience, and wildfire probability. Using the Great Basin as a case study, we found that CSI decreased by 53% basin wide from 1989 to 2020. Using the Sagebrush Conservation Design’s sagebrush ecological integrity cate- gories across the Great Basin, we found that CSI in “core”areas remained relatively unchanged between 1998 and 2020 (decreased by 1%), whereas “growth opportunity”areas CSI began to change (decreased by 13%) and “other rangeland”areas CSI decreased by 67%. We found that CSI was able to act as an indi- cator for determining when carbon security would decrease several years prior to a wildfire disturbance, which then rapidly reduced CSI. Finally, we created a carbon security management map to help prioritize potential management for achieving greatest carbon security and locations for restoration. These results show that CSI provides landowners and land managers an opportunity to assess how secure their carbon is on the land and help them prioritize areas for restoration.