The Andes Mountains are the longest continental mountain range in the world, stretching over 7 countries in South America. It has over 100 active volcanoes and contains great biodiversity, including 30,000 plant species and over 1,000 amphibian species. The climate and ecosystems vary greatly from the wet Northern Andes to the drier Central and Southern Andes. Ancient civilizations like the Incas developed advanced irrigation for agriculture in the mountainous terrain, domesticating crops like potatoes and maize that still play an important cultural and economic role in the region.