As the Earth warms, its ice melts. This global melting is an early and obvious sign of climate change, but its implications go far beyond merely losing snow and ice. For starters, some people and ecosystems depend on the ice — glaciers for water supply in areas of seasonal rainfall, for example, and sea ice for habitat.
The melting of land ice is already raising sea levels. In some fairly likely scenarios, oceans would rise by meters worldwide with devastating results. A sea level rise of just one metre would displace tens of millions of people in Bangladesh alone. All of this melting ice could dilute the world's oceans - changing the salinity enough to hurt fish stocks and disrupt ocean circulation patterns globally.
Then there is the chance that melting ice will cause a feedback effect due to the fact that snow and ice reflect more sunlight than bare ground or water so less ice means more warming (which melts more ice, etc.).