The East Kalimantan Programme has focused on connections between natural processes, biological variability and human activity in the deltas of the rivers Berau and Mahakam. The physical processes, mangrove dynamics and socioeconomic developments in these two Indonesian coastal regions have been investigated to reveal the impacts of changes in land-use, hydrological processes and geomorphological developments in upstream areas. The two deltas show contrasting conditions. The Berau Delta has a relatively small catchment area, whereas the Mahakam catchment covers a significant portion of the island of Borneo, and includes a number of lakes buffering the river discharge. These differences are reflected in distinct time scales at which delta developments take place. Although economic activity has started much earlier in the Mahakam Delta, geological records still show relatively few signs of human influences. The human control on the Berau Delta, despite being considered relatively pristine, is rapidly gaining strength.