Final answer:
Rising sea levels are caused by increased ice melting and thermal expansion due to global warming. This has significant impacts on the environment, including the loss of habitats and coastal flooding. The intrusion of saltwater into freshwater systems can also affect the availability of clean drinking water.
Step-by-step explanation:
Rising sea levels are primarily caused by two factors: increased ice melting and thermal expansion due to global warming. The melting of land ice, such as glaciers, adds water to the ocean, while the melting of sea ice does not contribute to sea level rise since it is already displacing its own volume. As the Earth's temperature rises, the density of water decreases, resulting in a larger volume and higher sea levels.
This rise in sea levels has significant impacts on the environment. Coastal habitats and cities are at risk of flooding and destruction, leading to the loss of valuable ecosystems, displacement of human populations, and damage to infrastructure. Additionally, the intrusion of saltwater into freshwater systems can affect the availability of clean drinking water.