The Isthmus of Panama is a land bridge whose appearance 3 million years ago enabled the Great American Biotic Interchange, in which animals and plants from the north colonized the south, and vice versa.[1]

In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea levels fall, exposing shallow, previously submerged sections of continental shelf; or when new land is created by plate tectonics; or occasionally when the sea floor rises due to post-glacial rebound after an ice age.

Prominent examples

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Map of Sahul and Sunda, land masses that have provided land bridges at various points throughout the Pleistocene

Former land bridges

Current land bridges

Land bridge theory

The botanist Joseph Dalton Hooker, noting similarities of the floras of Australia, New Zealand, and southern South America in his six-volume Flora Antarctica, published between 1844 and 1859, proposed that land bridges had once existed between these land masses.[2]

In the late 19th and early 20 centuries, vanished land bridges were an explanation for observed affinities of plants and animals in distant locations. Such scientists as Joseph Dalton Hooker noted puzzling geological, botanical, and zoological similarities between widely separated areas, and proposed land bridges between appropriate land masses that allowed species to spread between land masses.[2][3] In geology, the concept was first proposed by Jules Marcou in Lettres sur les roches du Jura et leur distribution géographique dans les deux hémisphères ("Letters on the rocks of the Jura [Mountains] and their geographic distribution in the two hemispheres"), 1857–1860.[3]

Hypothesized land bridges included:[3]

The theory of continental drift provided an alternate explanation that did not require land bridges.[4] However the continental drift theory was not widely accepted until the development of plate tectonics in the early 1960s, which more completely explained the motion of continents over geological time.[5][6]

See also


  1. ^ a b Webb, S. David (23 August 2006). "The Great American Biotic Interchange: Patterns and Processes". Annals of the Missouri Botanical Garden. 93 (2): 245–257. doi:10.3417/0026-6493(2006)93[245:TGABIP]2.0.CO;2. S2CID 198152030.
  2. ^ a b Winkworth, Richard C. (2010). "Darwin and dispersal". Biology International. 47: 139–144.
  3. ^ a b c Corliss, William R. (June 1975). Mysteries Beneath the Sea. Apollo Editions. ISBN 978-0815203735. Chapter 5: "Up-and-Down Landbridges".
  4. ^ Holmes, Arthur (18 April 1953). "Land Bridges or Continental Drift?" (PDF). Nature: 669–671.
  5. ^ Le Pichon, Xavier (15 June 1968). "Sea-floor spreading and continental drift". Journal of Geophysical Research. 73 (12): 3661–97. Bibcode:1968JGR....73.3661L. doi:10.1029/JB073i012p03661.
  6. ^ Mc Kenzie, D.; Parker, R.L. (1967). "The North Pacific: an example of tectonics on a sphere". Nature. 216 (5122): 1276–1280. Bibcode:1967Natur.216.1276M. doi:10.1038/2161276a0. S2CID 4193218.

Further reading