Natural Corridors typically follow geographic features, like mountain ranges or rivers. Most Large-scale Corridors incorporate Natural Corridors, and were once large continuous blocks of habitat.
Natural corridor examples
Riparian zones are natural corridors that help sustain subpopulations within a constantly shifting landscape. The St. Francis’ satyr butterfly on Ft. Bragg is dependent on ephemeral wetlands along stream corridors to disperse into emerging suitable habitat. Suitable habitat is determined by beaver and fire activity, and as a result is constantly shifting. To sustain the larger metapopulation, individuals must be able to travel along riparian corridors to find a developing patch. Without these natural corridors, subpopulations would become isolated and lose their ability to disperse effectively.
Migratory birds and insects have a strong need for corridors, even though they spend much of their time in the air rather than on the ground. Connected corridors provide habitat for resting and feeding, and ensure that species are able to continue on their migratory journey without encountering large gaps of unsuitable habitat. Protection of these “flyways” as natural corridors for migratory species is critical to ensure that they are able to reach desired breeding or wintering grounds. The United States has four main migratory flyways: the Pacific Flyway, Central Flyway, Mississippi Flyway and Atlantic Flyway.
Similar to terrestrial ecosystems like the Greater Yellowstone Ecosystem, marine ecosystems can support naturally occurring corridors within the larger expanse of the ocean. In the Pacific Ocean, two main corridors are used by marine wildlife: the California Current, which flows south along west coast of North America, and a trans-oceanic corridor called the North Pacific Transition Zone, which forms the border between cold sub-Arctic waters and warmer subtropical waters. These areas tend to attract large numbers of individuals due to high prey abundance such as zooplankton and fish, which in turn attract large predators. Species that use these corridors include whales, sharks, seals, seabirds, turtles and tunas.