The Great American Biotic Interchange and the Panama Canal

It was nearing the end of the tertiary period, when continents had long broken up from the Pangaea that they once made up. North and South America were not connected, but as is the nature of earth everything was still changing. The Pacific plate was travelling eastwards slowly underneath the Caribbean plate, causing underwater volcanoes to form islands (the central American volcanic arc) which along with parts of the sea floor were pushed upwards and together. When finally merged with sediment from the north and south continents around 2.8 million years ago (during the pliocene) a bridge was formed, which is what you know today as Panama or the Isthmus of Panama.

This geological activity led to a significant ecological event- the Great American Biotic Interchange. Just like the movement of humans through ice ages for example, a new opportunity had opened for prehistoric plants and wildlife- to explore and utilise new jungles, waters, land and prey. Focus within ecology surrounds the mammals that this event effected. In their waves, sabre tooth cats, bears, wolves, wolverines, tapir and members of the gomphothere family (extinct elephant like mammals) all travelled south while ground sloths, capybara, giant armadillo, opossums and the notoungulate travelled north. Non-mammal travellers from south to north included the terror bird (a giant flightless, carnivorous bird).

North American migrants were much more successful than south- around fifty percent of land mammals in South America today have descended from North American immigrants of the Great Biotic Interchange, compared to around 20-30 percent the other way. This was due to a few factors- climate (southern mammals found it harder to adapt to colder, drier conditions after life in the tropics) and there were much more northern than southern carnivores. The oceans were affected too - access for the deep sea that once flowed between was closed off, resulting in a change of currents which led to a number of new currents- one of which was the beginning of the gulf stream.

It is worth noting that there there is some scientific discussion about whether or not the isthmus of Panama was indeed formed around 3 million years ago, or in fact many million years prior. (http://advances.sciencemag.org/content/2/8/e1600883.full)

The Panama Canal

A short leap of a 3 million years later intercontinental trade, exploration and colonial missions were expanding. The jungle bridge of Panama that catered for the mass migration millions of years ago now stood in the way. Alternatives to the shipping journey around the entire continent, or across the 47 mile rainforest were being planned by the French empire. It was the late 1800s and over a decade parts of the Panama jungle were deforested and a trench was built, which would essentially close back up with mud during each heavy rain season. The dig had to become as wide 3/4 of a mile, and 100m deep in order to actually maintain a trench through the seasons. Around 22 thousand workers brought in by the French died during this attempt at the canal from diseases such as malaria, yellow fever and dengue together with the dangerous, harsh swamp-like working conditions. There are also known to have been racial injustices within the workforce, which are explored in "Colón Man a Come: Mythographies of Panamá Canal Migration", by Rhonda D. Frederick (see reference at end). "Panama was four times more deadly for the black man than it was for the white", she quotes from McCullulogh (1977). This attempt was abandoned due to bankruptcy and the french leaders, de Lesseps and Eiffel (who the tower was named after) were prosecuted for handling business unlawfully.

Illustration of the dangerous construction site of the Panama Canal, by Benjamin von Eckartsberg.

The project was later picked up in 1904 by America under Roosevelt's lead. America persuaded Panama (which was at the time a part of Columbia) to let them complete the canal in return for support of Panama to become it's own country. This canal project became something much bigger. Using dynamite instead of manpower, 164 square miles of forest, the Culebra mountains, towns and infrastructure that had been built during the French attempt were cut through and removed to create the manmade lake of Gatun. While the building techniques were bigger and stronger than before, some things hadn't changed. The majority of the workforce had arrived from the Caribbean, to be treated as poorly as those before them. But the project went on and a decade later as WW1 began, the first ship was to make the first trip between the Pacific and Atlantic oceans since the fish and sea mammals that had passed through before the Great American Interchange. The canal over the decades has been seen by some as an imperialistic mission as it remained under North American ownership with much less economic benefit to the people of Panama in comparison- after riots though the 60's, they eventually gained control of the canal themselves in 1999.

Today, 5% of all global trade passes through the canal, via around 14000 ships a year.

(There is so much to this historical story- if you are interested in finding out more see the book by Rhonda D. Frederick or 'The Path Between the Seas' David McCullough)

Video illustrating how the Panama Canal works, Business Insider.

References

"Colon Man a Come":

https://www.amazon.co.uk/Colon-Man-Come-Mythographies-Migration/dp/0739108913

"The Path Between the Seas":

https://www.amazon.co.uk/Path-Between-Seas-Creation-1870-1914/dp/0671244094/ref=sr_1_1?s=books&ie=UTF8&qid=1522671517&sr=1-1&keywords=The+Path+Between+the+Seas

https://earthobservatory.nasa.gov/IOTD/view.php?id=4073

https://www.youtube.com/watch?v=PddQvyiBfdc

https://www.youtube.com/watch?v=WR_hCMR2Xvc&t=151s

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2987556/

http://thatslifesci.com.s3-website-us-east-1.amazonaws.com/2016-09-27-When-and-how-terror-birds-invade-EFusco/

http://advances.sciencemag.org/content/2/8/e1600883

(http://blogs.ei.columbia.edu/2014/03/31/the-isthmus-of-panama-out-of-the-deep-earth/)