The Western Hemisphere’s two major ecozones are separated by the Isthmus of Panama.
The Isthmus of Panama or know as the Isthmus of Darien is the small strip of land that is situated between the Pacific Ocean and the Caribbean Sea. It links the South and North America and contains the Panama Canal and the country of Panama.
If there are mountains, people can not get over them easily
The Delta is formed at the western edge of the Central
Valley by the confluence of the Sacramento and San Joaquin rivers. It was
created since the last day of the Ice Age. The role of the Delta in the two
major water systems is to deliver water
for irrigation in the San Joaquin Valley and municipal water supply for
southern California.