Limitations of Existing Carbon Calculators for Riparian Forest Plantings

Executive Summary

Forests play a critical role in capturing carbon and reducing greenhouse gas concentrations in the atmosphere. Restoration of forest cover provides efficient, cost-effective carbon capture while also supporting biodiversity and providing flood mitigation, nutrient retention, and temperature regulation, especially when planting native forest cover occurs in floodplains and along rivers and streams. Riparian forest restoration projects usually begin with biodiversity or water quality outcomes as their primary goal, but organizations, policies, and programs focused on climate solutions increasingly recognize the role riparian forests and buffers can play in reducing carbon dioxide. To meaningfully measure how these projects contribute to natural climate solution goals, we need transparent, efficient, and robust tools that can estimate the amount of CO₂ sequestered in riparian plantings.

Many tools exist which can quantify carbon sequestration and storage in the forest sector. But fewer of these 'carbon calculators' are applicable outside of upland forests or for woody vegetation types not used for timber production. like riparian forests or buffers. We tested available carbon calculators to see if, using riparian forest project planting plans, we could reliably estimate the carbon benefits of these projects. We measured trees and woody shrubs in 15 plots across a for a 5-year old, 44-acre riparian forest planting in the southern Willamette Valley. After using allometric equations to estimate the carbon stored in trees and shrubs, we compared the estimates from the carbon calculators to field-based empirical carbon estimates. We expanded upon this case study using data from 5 additional sites, ranging from 5 to 21 years old, for which we had access to planting plans and empirical carbon storage estimates as part of a larger study of carbon in riparian planting in western Oregon.

Suggested Citation

Graves, R.A. (2025). Limitations of existing carbon calculators for riparianforest plantings: how do carbon calculator estimates compare to field-based carbon stock estimates? The Nature Conservancy.