The Dangerous Disappearance of Delta Dirt

Abstract

Across the Sacramento-San Joaquin Delta, spongy soil is sinking at a rapid rate! This issue, known as subsidence, happens in places with peat soils that have been drained. Peat soils are created over thousands of years by decaying wetland plants. Following European colonization of California, the Delta’s wetlands and their peat soils were drained, and levees were built to keep the land dry. Farms now thrive on this fertile landscape. However, as drained soils are exposed to oxygen, tiny microbes rapidly consume the peat soil, which makes the land sink. Now, many Delta islands look like giant salad bowls up to 9 m deep, with fragile levees holding the rivers back. This puts communities, farms, ecosystems, and water supplies at risk from floods. The microbes in the soil release carbon dioxide into the atmosphere, which contributes to climate change. Scientists and land managers are creating new wetlands to combat subsidence in the Delta.