Mangrove forests have a very important role as a provider of environmental services and economic support. The existence of mangrove forests in Seruyan Regency has suffered significant damage. The purpose of this study was to determine the most dominant type of mangrove landcover conversion and to calculate the rate of change. The method of analyzing changes in mangrove landcover using multitemporal Landsat images with visual classification. The classification accuracy test reached a value of 88%. The results of spatial analysis with a span of 41 years found a decrease in mangrove landcover area of 69% with an average rate of change of 71 hectares per year. The dominant cause of the decline in mangrove landcover is the landclearing of ponds, which has an average rate of change of 82 hectares per year. This activity has an impact on decreasing the diversity of mangrove vegetation types. In mangrove forests found at least two to five types of mangroves with sparse to dense densities, whereas in ponds as a result of pond clearing they are only found on the edge of ponds with sparse densities.