OOS 44-8
Can carbon credits fund riparian restoration?
Society is increasingly calling on ecological restoration to renew or sustain the flow of ecosystem services to humans. Meanwhile, payment-for-ecosystem-services (PES) schemes are being developed worldwide to compensate landowners for services like water purification and carbon sequestration. Cap-and-trade programs for greenhouse gases now operational in California and in the Northeast-Mid Atlantic region have PES components in which private landowners and some public agencies can earn carbon credits for reforestation. I asked if the carbon credits earned by riparian restoration along the Sacramento River would be sufficient to offset the costs of restoration plantings. Making use of a chronosequence of riparian restoration sites, I calculated the trajectory of carbon credits earned over two decades, and compared them to costs associated with planting and verification of the credits.
Results/Conclusions
Riparian forests added 3.25 Mg C/ha/yr in tree biomass and approximately 1.07 Mg C/ha/yr shrub, herbaceous, and soil carbon. This rate of carbon sequestration has the potential to earn a maximum of US$3390/ha in credits after 20 years, not counting costs. However, the variability of carbon inventory estimates was so high that the carbon accounting protocol imposed a "confidence deduction" of 100% at all sampling dates, resulting in no credits being earned. Reanalysis of the data, using a different sampling strategy to reduce the confidence deduction, yielded carbon income of US$1379/ha, which represents 70% of actual planting and verification costs. Carbon payments alone are therefore unlikely to incentivize reforestation in this ecosystem. However, conservation easements needed to ensure the perpetuity of the credits would provide an additional source of income for private landowners. Also, public agencies may find the 70% offset of costs a substantial benefit. Finally, this analysis may overestimate the confidence deduction because it is based on a chronosequence and not plots measured repeatedly over time.