What impacted the Aborigines almost immediately when English settlers arrived?

Disease: One of the most devastating impacts was the introduction of foreign diseases, such as smallpox, measles, and influenza. These diseases did not exist in Australia before European contact, and the Aborigines had no natural immunity to them. As a result, epidemics swept through the Aboriginal population, decimating communities. It's estimated that up to 90% of the Aboriginal population died from disease in the first century of European settlement.