Here, we outline a conceptual framework for biodiversity dynamics following environmental change. The model incorporates lags in extinction and immigration, which lead to extinction debt and immigration credit, respectively. Collectively, these concepts enable a balanced consideration of changes in biodiversity following climate change, habitat fragmentation and other forcing events. They also reveal transient phenomena, such as biodiversity surpluses and deficits, which have important ramifications for biological conservation and the preservation of ecosystem services. Predicting such transient dynamics poses a serious conservation challenge in a time of rapid environmental change.