Answer:
Three major environmental challenges in Oceania are:
1. Sea level rising; The rising of the sea level is presenting a huge challenge and danger for multiple island countries in Oceania. This is because some of the islands have very small elevation, and are in danger of getting bellow the water level with the current trends of the sea level rising.
2. Erosion; The climate in Oceania is warm and humid, and those are the perfect conditions for rapid erosion. Since most of the islands are relatively small, any loss of land because of erosion means less arable land, less stable land, less land mass in general.
3. Water pollution; Even though it is not the Oceania's countries to blame for it, the water pollution in the Pacific is increasing and causes more and more damage to the biodiversity in the region. Since the people living in Oceania are heavily dependent on sea food, this is becoming bigger and bigger problem, that can lead to either sea food with toxic materials, or insufficient food from the sea
