The primary concern about global warming is the melting of the polar ice caps. As the caps melt, ocean levels rise. This will cause coastal areas to flood and reduce the amount of land available, both for humans and terrestrial animals. Another concern is that some animals are sensitive to temperature; even a few degrees can cause major changes in their behavior, physiology, and even gender ratios. Some species of reptile's sex determination is cause by the temperature the eggs are exposed to; if the temperatures are too high, they may be all male or all female.