For "recent" extinctions, see Holocene extinction. The first of five great mass extinctions was the Ordovician-Silurian extinction. For instance, there are ambiguities around the timing of sudden extinctions of Australian megafauna. Other lineages have arisen and then become extinct, sometimes during severe mass extinctions. Bolide impacts can be dramatic triggers of mass extinctions. Other human factors have led to declines and even extinctions in seabird populations and species. Overexploitation can lead to resource destruction, including extinctions. Habitat loss is the leading cause of both species extinctions and ecosystem service decline. Many of these extinctions occurred during or shortly after the last glacial period. Rapid environmental changes typically cause mass extinctions. Evidence shows that this adaption occurred due to dramatic mass extinctions in the Permian period. There is no definitive evidence of impacts leading to the three other major mass extinctions. This matches the geologic record of significant extinctions during the Phanerozoic Eon. Since the Cambrian explosion there have been five distinctly identifiable mass extinctions. Hypotheses have also advanced toward linking reversals to mass extinctions.