Renaturation and reforestation of mangrove forests and their importance as CO2 sinks: Mangroves, the tidal forests along tropical and subtropical coastlines, allocate a disproportionately high amount of carbon per area unit compared to other forest biomes of the world. Thus, mangroves are considered an important nature-based tool for climate change mitigation by their high carbon sequestering capacity. On the other hand, mangroves are one of the most seriously threatened ecosystem of the world due to deforestation and anthropogenic conversion, with loss rates higher than those of tropical rain forests – potential carbon sinks become carbon sources, amplifying climate change. As mangroves achieve many other ecosystem services beside sequestering CO2, initiatives and projects for the rehabilitation of disturbed or lost former mangrove forests increased in recent times. As these measures are labor-intensive and often not successful, they must be critically considered. In addition, as mangroves are spatially restricted by very distinct site conditions, their effect for carbon sequestration on a global scale is limited. On a local scale, however, in particular for countries with low CO2-emissions and extensive coastlines, mangroves can play a more substantial role for climate change mitigation, if deforestation of mangroves is stopped, their areal extent enlarged and additional programs for reducing CO2-emissions are implemented.