the lesser known biology behind the Panama Canal construction

I have wanted to see the Panama Canal from the “inside” for some time. My great uncle, a railroad civil engineer from Iowa, went to work there in the early 1900s, to assist John Stevens (who was appointed by Teddy Roosevelt to oversee the whole canal project) with completing the railroad that would carry tons of dirt away from the canal construction.

Modern day construction of the Panamax canal was approved by Panamanian voters in 2006 and used the same principles that Stevens established in construction of the original two canals a century earlier. The much wider Panamax Canal accommodates “super-ships”, i.e., large cruise ships and container ships that would not fit through the smaller, original locks.

The U.S. took over the Canal project from France in 1904, and within a decade had engineered one of the most difficult and dangerous constructions ever undertaken — a canal to connect the Pacific and Atlantic Oceans through a narrow isthmus of land in Panama. Instead of engineering a flowing river between the two oceans (which are actually 22 cm different in height), Stevens envisioned moving ships through a series of locks to raise ships up from the Pacific to a reservoir and then lower them again to the Atlantic side.

First of the two Miraflores locks from the Pacific. The third (Pedro Miguel) lock is located above Miraflores lake, and ships pass from there through the narrow channel of the Culebra Cut, another engineering feat that created a channel through the mountains of the Continental Divide, and on into one arm of Lake Gatun. See map below.
Approaching the first lock we could see the rail system on which the “mules” that assist ships through the lock travel. In the distance on the right is the 4-story building housing the Visitor Center for the Canal.
Water drains into the first lock to raise the ship to the level of the second lock in just a few minutes, at which point the gates in front of the ship fold back into the sides of the canal — as seen below.
The forward “mule” attached to the bow of the ship by two cables runs in exact tandem with one on the other side, helping to keep the ship in the center of the canal. The ship’s aft thrusters propel it slowly through the lock. There was only a couple of inches between the ship and the side of the canal in this lock.
Looking back (aft) at our passage through the lock and the Bridge of the Americas at the opening to the Canal. Ships can pass in both directions through the two side-by-side canals, but it requires precise programming for the many ships moving east and west. Reservations must be made months in advance. Transit is not cheap and is determined by size and weight of the vessel — it cost $375,000 for our ship to go through the entire passage. To move a private yacht through the canal might cost $2000, and even swimmers must pay a cost — one was charged $.36! Heavily laden container ships can off-load their cargo at the canal entrance and move the containers by rail in order to avoid the high cost of transit on the canal.
Map of the lock system of the Panama Canal by By Thomas R├Âmer/ (OpenStreetMap data, CC BY-SA 2.0), Everything you ever wanted to know about the Panama Canal passage — elevation profile, lock placement, and route of ships through the passage.

But it isn’t the engineering feats that I want to showcase here. The canal could never have been completed without solving the real dangers of working in this part of Panama: yellow fever and malaria, which killed tens of thousands of French and Americans in the early stages of canal construction.

Colonel (Dr.) William Gorgas, the scientist who saved the Canal project by eliminating mosquito-borne disease from the Canal Zone. (Photo from his Wikipedia page)

Along with Stevens, Teddy Roosevelt appointed Colonel William Gorgas (a physician by training) as chief sanitation officer, with the charge of eradicating yellow fever and controlling malaria in the nearly 500 square miles of dense canal-zone jungle. Fortunately, Gorgas knew from previous research on these diseases that they were a result of mosquito-borne infections, and not transmitted person to person through the air like a flu. His campaign enlisted 4,000 workers in “mosquito brigades” to clean up mosquito breeding areas by draining swamps and spreading oil on the surface of standing water, installing window screens and tight-fitting doors in living areas, fumigating living and working areas with pyrethrum insecticide and sulfur, and establishing protocols for administration of anti-malaria medication.

Aedes aegypti, the “yellow fever mosquito” also transmits West Nile Virus, Dengue, and Zika virus. Hundreds of years of trade between Africa and the Americas, especially the transport of slaves, brought these mosquitoes and their virus parasites to the New World. (From “Mosquito of the Month”, VDCI)

Two years after establishing intensive sanitation protocols, the two diseases had nearly been eliminated, and the productive construction of waterways and locks began. Gorgas was as much a hero of the Panama Canal construction as Stevens and the engineers who followed him on the project. Obviously, without controlling the disease and protecting the health of canal workers, the project could never have been completed.

After a long 12 hours of slow progress through locks and Gatun lake, we exited the Canal through the Gatun locks, passing under the Atlantic bridge and on into the Caribbean Sea of the Atlantic Ocean. A long but fascinating process, including all the history and appreciation of the science and engineering that went into it to make the Panama Canal what it is today.

In the “backyard” of the Panama Canal

After 10 days of ship travel, at last we reached the entrance to the Panama Canal and our passage to the Atlantic Ocean and Caribbean. It took almost 12 hours to transit the 50 miles of the canal, through three sets of locks on the Pacific side, into huge Lake Gatun, and then through three sets of locks on the Atlantic side.

We began our journey through the Canal at 6 a.m., just as the sun was coming up.
A couple of female Frigate birds flew over to check us out. These are soaring specialists that cruise the oceans looking for fish and squid, and often steal a meal from other birds (like Boobies). They may follow large ships (i.e., frigates) which often scare up fish in their wake.
The Bridge of the Americas (which goes into Panama City) looms over the entry to the Canal. This is the main entry to both the new Panamax (super large ship canal) and the two older, original canals.

I was particularly interested in getting a look at the islands in Lake Gatun, which was formed by damming the Chagras River at a narrow point near its mouth on the Atlantic side (see map below near Gatun locks) back in 1913. When dammed, the river then flooded a once wide valley forming a large lake with just the mountain tops projecting up forming a series of small and large islands in the lake.

One of the largest islands, Barro Colorado (circled in black on the map), was set aside as a nature reserve in 1923 and has been administered by the Smithsonian since then. With almost 100 years of climate and biological data, it is one of the most studied tropical forest systems in the world.
Small lakes on the sides of the main part of the canal serve as reservoirs for circulating water through the locks.
Drainage systems collect rainwater from the surrounding hills to channel it into the main waterway. Vegetation along the banks of the canal is sparse to allow water runoff, while the hills behind are more mature rainforest.
Larger islands in Lake Gatun have undisturbed tropical rainforest with an amazing biodiversity of plants and animals. The first census in 1982 recorded over 300 tree species in a 100 acre plot on Barro Colorado Island!

This area of Panama receives about 100 inches (i.e., 8 feet!) of rain annually, but almost all comes during the rainy season. During the dry season between December and April, less than 3 inches of rain falls and many of the island streams dry up. The soil becomes so dry, large cracks develop in it. Flowers and insects disappear, trees stop producing fruit, and animals on the island become food limited.

As a result of changes in the forest structure with limited island land surface and the size of the islands themselves, species diversity of animals, and especially birds, is markedly lower than that of intact rainforest on the hillsides of the canal — as you would expect. Researchers have found smaller numbers of under-story bird and mammal species, and there are no large mammalian carnivores to control the herbivore populations. But food is a limiting factor here.

Islands (really hilltops) in Lake Gatun dot the lake surface. It spans 164 square miles in all, and makes up about 20 miles of the length of the waterway from the Pacific to the Atlantic.
Black Vultures soared over the hilltops of some of the islands in the far distance.
Plants growing on top of plants all the way down to the water’s edge — that’s tropical diversity! Imagine trying to hack your way through this forest from one end of an island to the other…

National Geographic produced an interesting video featuring some of the work that has been done on Barro Colorado Island in 2007: Panama Wild — Rainforest of Life. If you like nature videos and want to know more about this area of the world — click on the video below.