The Saga of Diego Garcia Continues with:

Division of Ecological Perplexities Presents:
Nature: Red in Tooth and Claw!
The General Ecology of Diego Garcia

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Well, since I majored in Environmental Biology at the University of Montana way back when, I was always walking around wherever I was stationed and looking at the flora and fauna, trying to figure out how it all fit together in that particular ecosystem.  Diego was an especially interesting place, because it was surrounded by an untouched reef of fabulous diversity, while the environment on the island itself was completely artificial - that is altered by human habitation beyond all recognition of its pre-human state.  A lot of the information I have about the island came from the Atoll Research Bulletin No. 149, August 27, 1971 from the Smithsonian Institution, Washington DC, titled “Geography and Ecology of Diego Garcia Atoll, Chagos Archipelago” edited by D.R. Stoddart and J.D. Taylor, and form "Ecology of the Chagos Archipelago" edited by Charles R.C. Sheppard and Mark R.D. Seaward.

As for animal life, the island is composed of coral rubble and sands laid down since the last Ice Age (about 12,000 years ago - the period since then is called the Holocene).  Beneath that, about 60 feet below sea level, there is limestone which was the island during the last Ice Age (called the Pleistocene, which lasted about 2 million years).  Because of the sand & gravel nature of the Holocene deposits, fossil evidence of terrestrial fauna is entirely lacking.  However, it's possible that the islands are very young - according to Stoddart in 1971, the surfaces did not peek above sea level until 2,000 to 5,000 years ago (the Holocene began when the ice sheets melted which caused the sudden 60 foot rise in sea level - it took corals thousands of years to grow up to the new sea level).  A couple thousand years isn't generally considered enough time for endemic species to evolve.  However, it is estimated that during the last ice age, the Chagos comprised some 13,000 square kilometers of land, for at least 200,000 years.  What we see today is a sandy island perched on the very top of the mountain that previously existed.  Because of it's isolation, there may even be remnant populations of animals evolved during the Pleistocene.  Let's face it, the Chagos archipelago, including Diego Garcia, was never very heavily populated, and it's possible something still remains for you to discover!
The island was uninhabited when discovered by the Portuguese explorers in the 1500's, and remained so until the French arrived in the 1790's to establish coconut plantations.  Of course, as was the custom in those days, the French themselves did not do the work on the plantations, but imported slaves, primarily from Madagascar and their colonies of Mauritius and Reunion (the latter two were, like Diego, uninhabited when discovered by the European explorers - and home to the famous, but soon extinct, Dodo birds).  Based on linguistic remnants, it appears most of the slaves ancestors originated in what is today Mozambique.  At any given time, about 500 - 1,000 people lived on Diego Garcia during the "Plantation Era" from 1786 - 1971.

Above left - Calophyllum inophyllum (Takamaka tree).
Above right - a bryophyte growing out of an old stump.
Below left - Ficus benghalensis, commonly called the Banyan Tree.
Below right - A path through young coconut trees (Cocos nucifera).   The invasive coconut can be legitimately called a "weed" on Diego Garcia!

Below:  A Banyan Tree takes over the outdoor latrine at the East Point Plantation Manor House.  This plantation was abandoned in 1971, and this photo was taken in 1987.  The "jungle" works fast!

Originally, Diego was covered by hardwood forests.  Some remnants remain at Point Marianne, Mini-Mini, and around the plantation area.  According to the ARB #149, all the rest of the broadleaf hardwoods were turned into lumber and shipped back to Madagascar and Mauritius by the first French "settlers" in the process of clearing the island for the plantations.   In their place, various plants in addition to coconuts were imported by the French and later the British.  The most common was what everyone called "Scaviola" (Scaevola taccada) bush, which is a broad-leafed succulent growing to about 20 feet tall on DG, mostly along the shore - as seen in the composite photo of the entrance to Barachois La Paille Sec, which we called "Shark Cove" below.

 The Entrance to "Sharks Cove" (a.k.a. Barachois La Paille Sec - which means "dry straw")

My buddy Steve Swayne at one of the entrances to Barrachois Maurice, near the East Point Plantation; 1982.

Above:  The interior of Barachois La Paille Sec with the tide almost out.  The sea grasses you see on the left dry out between tides and probably resulted in the name of the barachois.
Below:  Barachois Barrer (the central barachois of "Turtle Cove") at low tide.

One of the most interesting features of the island were the "barachois" which has no direct translation, but most people convert it to "cove".  For example, the three intersecting Barachois of Sylvain, Barrer, and Courpat are now collectively called Turtle Cove.   In the photos above, Steve is standing in the mouth of Barachois Maurice, which is about half way between GEODSS and the Plantation.  These barachois are lagoons off the main lagoon, and there are several on the southeastern leg of the island, from the south tip around to the northeast to the area of the Plantation (Barachois Lubine).  These barachois were generally dry at low tide, and filled with the high tide.  As tides on DG only ran about 3 feet, these barachois were regularly bathed in shallow water twice a day.  The tide ran swiftly through the gaps, and it was always interesting to watch schools of minnows, small fish, sharks, and turtles come in and leave with the tide.   I assume they were going in to eat (minnows eaten by small fish, which are eaten by small sharks, etc., ad nauseum), and you could clearly watch the Hawksbill turtles chowing down on algae which covered the coral ledges.  However, these barachois should not be confused with estuaries or salt marshes.  They were sea water fed and drained, period.

There is fresh water on the surface of Diego Garcia, but it doesn't "flow" anywhere.  Fresh water marshes around the East Point Plantation were reported by surveys in the 1960s.  There is a large freshwater marsh just NW of the USAF ("SAC") ramp on the airfield.  This apparently was a low spot on the island that when framed by the taxiway, parking apron and road, filled with rain water.  It was filled with aquatic weeds when I was there in 1988, and is reported to be the home of Bufo marina toads today.  There are several unstudied and virtually unknown fresh water ponds on the southeastern arm  of the atoll, running parallel to the ocean-side beach, west of the road, from the southern edge of the Bomb Dump south past the Donkey Gate and on for about 1.25 miles.  They can be clearly seen on "Google Earth" (as seen below).  There is no information that I can find about the origin of these ponds - whether they are natural fissures or "borrow pits" to build the road.  At any rate, when I took the picture of one of these ponds in 1988 (also seen below), there was nothing living in them that I could see other than algae, although there were hundreds of dragonflies in the air above them.  Hopefully, someone has stocked them with bluegill and bass by now, they would make great fishing ponds.

The Brits kept a very close watch on the environmental health of the island, and the east arm is kind of a wilderness area, and visitation by base personnel is limited and controlled.  Most of the lagoon is a designated RAMSAR (wetlands) preserve.  In 1988, there were three horses over on the east side, as well as donkeys.  I did see two of the horses, which were quite wild by that time, over by the Plantation in 1988.  I was told one was a gelding (those damned British Veterinarians must have caught the poor fellow) and the others a mare and a filly (never to become a mare with only a gelding around), so unless a stallion swam down from India, or snuck ashore off the Mary Jane, the horse population is extinct out there now, too.

I know elsewhere in this monologue, I've bad-mouthed the Brits a little.  However, the one thing I think they did pretty well was ensure the island was protected ecologically.  Basically they did this in two ways:  By making the USN keep the industrial pollutants contained and remove them from the island, and by making it a crime, punishable by the Magistrate of the island (the Brit Rep himself), for individuals to molest just about anything but insects (or each other, or, for most of us, ourselves).  For example, a permit was needed to travel to the east arm of the atoll, or to build a fire so that people wouldn't burn down the protective hedges along the coasts.  Once, I watched some BIOT police arrest a young sailor for pissing on a palm tree outside the Acey-Duecy Club (though whether it was for molesting the palm tree, or public indecency, I don't know).  Most especially, it was absolutely illegal to kill Coconut Crabs, Sea Turtles, and Spiny Lobsters.

The Brits attempted to control the predators on the island, to protect the sea birds and Coconut Crabs.  In 1971 and 72, the Governor of the Seychelles, who was also the Commissioner of the BIOT, had the SEABEES kill all a reported 800 dogs left by the Ilois when they were expelled from the island.  Some say they were shot, others that they were rounded up and gassed with exhaust from trucks.  They also killed all the pigs (I hope the pigs didn't die in vain, and at least provided a luau or two) leaving only rats and cats.  The Brits were always trying to kill rats, and made every attempt to control the cat population by rounding them up every once in a while, putting them in wire cages, and throwing them into the lagoon to drown.  Unfortunately, they were always catching the "dorm cats" which were basically pets fed and loved by the Americans, which caused a lot of hard feelings by the Americans.  It was reported that by 2006 there were only 3 cats left alive on the island.  Also, they then figured they had to control the chickens, since the cats weren't around to eat the chicks, and when the chicken population got out of control (because the cats had been drowned), the Brits would let the Filipinos catch them and eat them.

The Brits also tried to pay attention to the "TCN" (third country nationals - the Filipinos and Mauritian workers) on the island.  Though paid a very good wage, compared to what they would receive at home, these people brought their 3rd world concepts of nature with them.  Basically, this meant if they could catch it, they would eat it, and if it meant saving 50 cents for a meal they wouldn't have to pay for in their mess hall, then all the better.  At least as late as the 1980s they were always "poaching," and although no body cared if it was chickens, they also did not distinguish between sea turtle eggs and chicken eggs.  The classic example of what they were capable of was that the northwest end of the atoll was devoid of crabs and chickens, except in the American dormitory area, where the GIs and Sailors protected the cats and chickens.  South of the airfield was generally not visited by the TCNs, and there, the ecology, artificial though it was, was preserved from their appetites.   Unfortunately, this may be a preview of what is to come for Diego.  Unless there is an awakening of environmental responsibility on the part of the government of Mauritius when the island is eventually turned over to them, there is a good chance it will become, literally, a desert island.


A word now about "invasive species".  This is one of the hot topics in the environmental world.  Basically, it means a species not originally native to an area that has been introduced, either on purpose or accidentally, by man's activities.  The problem with invasive species is that they sometimes compete with native species for resources and can alter the natural balance.  Sometimes it leads to extinction of native species, either the competitor species or the prey species.  Modern examples are the Brown Tree Snake eating all the native birds on Guam and Salt Cedars displacing the Red Willow in the Rio Grande basin.  But after a while, nature balances itself out again, although extinction is sometimes the price.  So, generally, introduction of new species is considered a bad thing.

Unfortunately, sometimes it is too late to stop the invasive species, as things have already balanced out.  For example, on Diego Garcia, the terrestrial environment of DG is nothing like what it was before the arrival of humans.  Basically, the island was clear-cut of its native forest and replanted with coconut trees.  Over the next 150 years or so, all the terrestrial land birds were brought in (dove, fodys, mynahs, chickens, etc.) as were the rhinoceros beetles, earthworms, ants, toads, geckos, donkeys, cats, rats, horses, dogs (extinct since 1971), etc.  Also the scaevola was introduced as was the ironwood (pine-type trees) and any flowering trees and flowers you see out there.  These invasive species have now formed a biome in which they co-exist in relative balance.  The problem seems to be that the "native" species, such as coconut crabs, warrior crabs, sea turtles, and nesting sea birds have been impacted by SOME of these invasives, most notably the rat.  The coconut palm grows as a weed everywhere, and the dense jungle created by young trees effectively keeps the native hardwoods from getting re-established.

The UN has an agreement that says that the host nation (in this case the Brits) has an obligation to eliminate ALL invasive species, and some people want exactly that to happen.  Why?  What is wrong with the geckos and donkeys and chickens and earthworms?  Why would we cut down the Plumeria Trees and all the Ironwood?  To "restore" the native balance would basically require a scorched earth policy - take the island down  to coral sand and start all over.  And what was the pre-human ecology of the island?  No one knows for sure!  So why worry about it?  There is NO GOOD REASON!

It is absurd to even contemplate the UN's rules.  Do we want to bring back huge colonies of seabirds and keep sea turtle eggs from being dug up and eaten?  Sure.  So eliminate the cats and rats, and the seabirds and sea turtles will prosper, and that is a noble goal.  Cut down the coconuts and replant hardwoods.  Great idea.  But to go on and on and on as some do about eliminating all invasives, and using recent introductions like the toads and agana lizards to bash the Brits and the  Americans is pure politics.

DG will NEVER be what it was, and there is no good reason to try and make it so.


The real challenge has been the industrial wastes of the Island, and the Brits at least took their responsibilities rather seriously - and required the U.S. to play along.  The potential for pollution on the island came mainly from sewage from human waste, bulk metals, and POL (petroleum, oils and lubricants).  The USN has a very comprehensive plan for keeping the environment as pristine as possible, but let's be honest, unless the 'host nation' insists on conservation management, the US Military won't - it's not part of their mandate.  So the Brits are to be praised for saving Diego Garcia.

The "recyclable storage" area north of Seabreeze Village in 1987 - now it's the Golf Course.

There is a huge sewage plant on the central part of the northwest point of the island, and another near the airfield, both easily visible in aerial photos.  The sewage is treated in a tertiary plant - which is the best there is technically - with the last step disinfecting.  Outfall is down a pipe into the depths of the ocean.  Scientific expeditions in the 1990s and early 2000s report that the outfall is deep enough and diluted enough that the pollutant levels in the surrounding waters is "virtually pristine".

There was at one time a huge dump just north of the airfield, but in the 1980s the monthly supply ship, the Mary Jane, took away a ship load of that metal trash to Subic Bay for recycling on each visit, and most of it was gone by 1988.  It is now the island's 7-hole golf course and as can be seen on the golfing page on this website, the place shows no evidence of its former use.  The Navy still stores up metal and ships it off the island on ocassion.  Typically, the US ships the metal to the U.S., but beginning in 2006 began selling it to recyclers.  For example in 2006, Big Iron Trading Company made 3 trips to DG to salvage 10,000,000 pounds! of scrap metal in their ship the MV IRON BUTTERFLY, and paid $115,000 to salvage the stuff.  I guess recycling pays, but only $23 per ton.

There was also a landfill for biodegradable trash located about 2 miles south of the airfield, near I-Site South.  Again, scientific expeditions have found no trace of pollution from that site into the lagoon or freshwater lenses.

The fuel situation was the most challenging, since it involved the freshwater lenses.  On tropical "desert" islands like DG, fresh water is found just a few feet below the surface, even though there are no springs or streams anywhere.  What happens is that the rains (DG had an average of over 100 inches of rain a year) would seep into the sandy surface and displace or push out the salt water that would normally seep into the aquifer from the ocean and lagoon sides.  The freshwater would settle into a convex "lens" just below the surface.  There are several of these lenses on DG, and the freshwater for the island was extracted from them by an ingenious, computer controlled, complex well field.  The deepest wells are only 15 feet deep, and computers monitor the water pressure in the lenses, to ensure not too much water was extracted from any one lens, which would allow the salt water to intrude, and the process of rebuilding the lens begun again.  Rebuilding a lens could take years - flushing of the huge "Cantonment" Lens on DG would take 4 - 5 years, while the smaller lenses along the narrow portion of the islands would flush in just a year or two.  There are about 125 wells from the airfield north.  Ever wonder where the water comes from on DG?  Here's a diagram showing the three developed lenses (the airfield lenses are not currently in use as of 2008):

Approximate extent and depth of the Cantonment and Airfield fresh-water lenses on Northwest Diego Garcia.   The base uses over 100 shallow “horizontal” wells to produce over 150,000 gallons per day from the “Cantonment” lens.  It is estimated that this 900 acre lens, which is about 70 feet deep at it's deepest, holds 5 billion gallons of fresh water and has an average daily recharge from rainfall of over 2.5 million gallons, of which 40% enters the lens.  The other 60% is lost through evaporation and transpiration from trees - a coconut palm will transpire about 50 gallons a day!

There are also small lenses tapped for water at T-Site and GEODSS.

The airfield wells were drilled after the construction of the new runway, aprons, and fuel pits in the early 1980's.  Unfortunately, there were some leaks in the fuel system, and, as usual on military airfields in the 1970's and early 80's, all sort of solvents, cleansers, etc., were just hosed off the aircraft and the aprons into the nearest ditch.  There was a huge amount of fuel stored on the island, with underground lines leading from the POL pier near Pt. Marianne to the fuel storage areas and pits near the SAC ramp, and north of the airfield.  A lot of fuel leaked out into the freshwater lens at the airfield.  As I recall being told at the time that, there was an estimated one million gallons of JP-5 (which is the military name for "Jet A" fuel, which in turn is basically Diesel No. 2) in the lens, "floating" (because of its lower specific gravity) on top of tens of millions of gallons of fresh water, and that it was extracted using the water wells in place, and shipped back to the P.I. for re-refining, although the POL man at the time (Mel Wasikowski, now sadly deceased) told me that is was useable just as it came out of the ground.  Although this would be a novel way to store fuel for future use, it was not the politically correct solution!  So the fuel was extracted, and I guess by now the airfield lens has been restored.

Editor's Note 31 Mar 08:  Apparently they didn't get it all at first, or there were other leaks or spills.  From 1996 to 2003 the USAF conducted "bioslurping" to recover approximately 40,000 gallons of jet fuel from the "SAC Ramp" area.  Read all about it - direct from the EPA! Click here and go to page 2 of the PDF for the article "Large-Scale Bioslurping Operations Used for Fuel Recovery".


Earth First and Greenpeace, you're out of luck.  As much as you might like to "return" the island to its "natural" state, I don't think it could be done.  The existing ecology is pretty well balanced, with the cats eating the chickens and the rats, etc., and the donkeys kept pretty much in check by salt bloat (and thus dying young) and castrations.  Someone could rehabilitate the seabird population if they could kill all the rats and cats from the donkey fence on southward and up the east arm and replace the fence with a dike - creating a kind of wilderness area.  They could cut down the coconut trees and replant with broadleaf woodland.  Of course, that costs big bucks, and will probably never be done.  And of course, nothing will bring back the extinct local species that apparently lived there before old Don Diego Garcia arrived.  So, all you hard-core environmentalists out there, you've got two choices as I see it - 1)  Educate the 3rd world, and 2) Spend your money on restoration projects, rather than chasing that Norwegian whaling ship all over.  What?  You say #1 isn't politically correct?  And #2 is first priority?  All I've got to say is, if dolphins are so smart, how come they keep getting caught in those nets............(apologies to Dennis Leary).


Cindy Qoth's October 2000 Update - I was reading the Nature pages, and you mentioned geckos.  They are all over the place now!  I really don't recall there being many, if at all before.  It is really kinda creepy making rounds in the middle of the nite and walking some places in BEQ 14, one or twospots with 20 or so of them on the roof of the walkways and walls.  The make sort of a chirping croak...very weird.  At least they are cute.   The Cattle Egrets have taken the place of all the chickens, and are all over.  There is a chicken cull every quarter, where only the roosters are supposed to be taken.  Of course, the hens are, too, and it pissed off alot of people to have bitty chicks left to fend for themselves or get eaten by...things.  The frogs/toads whatever are all over the place...there were more until the rat poison was put out.  The rats were everywhere, so poison was put out.  Then there were less land crabs and frogs,  the flys fed off the rats,  and on up/thru the food chain.  The crabs must be getting hit worst, they eat the dead rats AND the dead frogs.  To top it all off, the chickens are getting inbred, with many more fluffy chickens than I recall being around before.  Fluffy ones don't have grown up feathers, more like downy feathers.

Mike Bodi's Submittal:  The SEABEES take part in the EARTH DAY, 1972:


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