The Netherlands has low-lying land areas below sea level protected by dikes and dunes, as well as higher land further inland. About half the country is below sea level, with the lowest areas no more than 3 feet above it. The Rhine and Meuse rivers deposited silt and gravel over time, creating fertile farmland. Peat soil was also used for farming, fuel, and salt production. The climate is mild with rainfall throughout the year. Several animal reserves help protect endangered species in the Netherlands like roe deer, red deer, and beavers whose natural habitats have been impacted by water pollution and development.