 During winter, extra-tropical cyclones sometimes pass south of Geraldton, generating winter gales with gusts of up to 35 metres per second, the wind direction from the northwest initially, then gradually moving around to southerly.Under the Interim Biogeographic Regionalisation for Australia (IBRA), the islands of the Houtman Abrolhos fall within the Geraldton Hills subregion of the Geraldton Sandplains region.The main biogeographic significance of the islands is their isolation, allowing them to provide refugia for such threatened fauna as tammar wallabies ("Macropus eugenii"), Australian sea lions ("Neophoca cinerea") and rare breeding seabirds.