Settlement activities of the Nok Culture considerably decreased around 400 BCE and ended around the beginning of the Common Era. For a better understanding of the decline of the Nok Culture, we studied the charcoal assemblage of the post-Nok site Janruwa C, dating to the first centuries CE. Janruwa C differs from Middle Nok sites in ceramic inventory and a wider set of crops. 20 charcoal types were identified. Most taxa are characteristic of humid habitats such as riverine forests, while those savanna woodland charcoal types that had been dominant in Middle Nok samples are only weakly represented. The differences between the Middle Nok and post-Nok assemblages do not indicate vegetation change, but rather different human exploitation behaviors. It seems that the Nok people avoided forest environments while in the first centuries CE, other, possibly new populations settled closer to the forest and were more familiar with its resources. The new exploiting strategies might be explained as adaptation to changing environmental conditions. Our results, together with data from other palaeo-archives in the wider region, point to climatic change as a potential factor for the decline of the Nok Culture. We argue that erosion on the hill slopes, maybe due to stronger seasonality, was responsible for land degradation after 400 BCE and that the Nok people were not flexible enough to cope with this challenge through innovations.