California has spent decades restoring wetlands in the Sacramento-San Joaquin Delta, hoping that reflooded farmland can rebuild soil, store carbon and help reduce greenhouse gas emissions. A new study published titled Interannual Variability in Greenhouse Gas Emissions Challenges Post-Restoration Net Sink Predictions in California Delta Wetlands in Global Change Biology found that the climate benefits of these projects can take longer to emerge than expected and vary substantially between sites and years. Researchers analysed 44 site-years of continuous measurements of carbon dioxide and methane exchange from six restored wetlands across the Delta. The results showed that restoration does not automatically turn a former agricultural landscape into a consistent greenhouse gas sink. Some wetlands remained sources of greenhouse gases years after restoration, particularly where vegetation establishment was delayed by high or inconsistent water levels. Others transitioned towards net climate benefits more quickly, highlighting the importance of restoration design, water management and long-term monitoring.
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