In many coastal and deltaic areas in the world, thick sequences of unconsolidated sediments have been deposited under conditions of Holocene sea level rise. In sediment-poor coastal and deltaic systems the created accommodation space was filled with peat instead of sediment. As a result, coastal and deltaic lowlands may comprise thick peat sequences and thus store large amounts of Holocene carbon in their shallow subsurface. In contrast to many other peatlands in the world, coastal and deltaic peatlands have been attractive areas for settlement by humans for thousands of years. Presently, they belong to the most densely inhabited areas in the world, exposing the carbon store as such to human influence. Human land use in peaty areas usually starts with dewatering, causing aeration and oxidation of peats. In this way, land use in coastal and deltaic areas is generally associated with release of carbon dioxide from the subsurface store to the atmosphere.