“CORAL atolls have proven over thousands of years that, if left alone, they can go up and down with any sea level rise. And if we follow some simple conservation practices, they can continue to do so and to support atoll residents. But they cannot survive an unlimited population increase, or unrestricted fishing, or overpumping the water lens, or unrestrained coral mining.”
These are the conclusions from Willis Eschenbach who lives in Honiara, Solomon Islands. He explains why:
“Much has been written of late regarding the impending demise of the world’s coral atolls due to sea level rise. Recently, here in the Solomon Islands, the sea level rise has been blamed for salt water intrusion into the subsurface “lens” of fresh water under some atolls. Beneath the surface of most atolls, there is a lens shaped body of fresh water which floats on the seawater underneath. The claim is that the rising sea levels are contaminating the fresh-water lens with seawater.
These claims of blame ignore several facts. The first and most important fact, discovered by none other than Charles Darwin, is that coral atolls essentially “float” on the surface of the sea. When the sea rises, the atoll rises with it, and when the sea falls, they fall as well. Atolls exist in a delicate balance between new sand and coral rubble being added from the reef, and sand and rubble being eroded by wind and wave back into the sea.
When the sea falls, more sand tumbles from the high part, and more of the atoll is exposed to wind erosion. The atoll falls along with the sea level. When the sea level rises, wind erosion decreases. The coral grows up along with the sea level rise. The flow of sand and rubble onto the atoll continues, and the atoll rises. Since atolls go up and down with the sea level, the idea that they will be buried by sea level rises is totally unfounded. They have gone through sea level rises much larger and much faster than the current one.
Given that established scientific fact, why is there water incursion into the fresh water lenses? Several factors affect this. First and foremost, the fresh water lens is a limited supply. As island populations increase, more and more water is drawn from the lens. The inevitable end of this is the intrusion of sea water into the lens. This affects both wells and plants, which both draw from the same lens. It also leads to unfounded claims that sea level rise is to blame. It is not. Seawater is coming in because fresh water is going out.
The second reason for salt water intrusion into the lens is a reduction in the amount of sand and rubble coming onto the atoll from the reef. When the balance between sand added and sand lost is disturbed, the atoll shrinks. This has two main causes — coral mining and killing the wrong fish. The use of coral for construction in many atolls is quite common. At times this is done in a way that damages the reef as well as taking the coral. This is the visible part of the loss of reef, the part we can see.
What goes unremarked is the loss of the reef sand, which is essential for the continued existence of the atoll. The cause for the loss of sand is the indiscriminate, wholesale killing of parrotfish and other reef-grazing fish. A single parrotfish, for example, creates about half a tonne of coral sand per year. Parrotfish and other beaked reef fish create the sand by grinding up the reef with their massive jaws, digesting the food, and excreting the ground coral.
In addition to making all that fine white sand that makes up the lovely island beaches, beaked grazing fish also increase overall coral health, growth, and production. This happens in the same way that pruning makes a tree send up lots of new shoots, and in the same way that lions keep a herd of zebras healthy and productive. The constant grazing by the beaked fish keeps the corals in full production mode.
Unfortunately, these fish sleep at night, and are easily wiped out by night divers. Their populations have plummeted in many areas in recent years. Result? Much less sand.
The third reason for salt water intrusion into the lens is the tidal cycle. We are currently in the high part of the 18 year tidal cycle. The maximum high tide in Honiara in 2008 was about 10 cm higher than the maximum tide in 1996, and the highs will now decrease until about 2014. People often mistake an unusually high tide for a rise in sea level, which it is not. There has been no increase in the recorded rate of sea level rise. In fact, the global sea level rise has flattened out in the last couple years.
What can be done to turn the situation around for the atolls? There are a number of essential practical steps that atoll residents can take to preserve and build up your atoll, and protect the fresh water lens:
1. Stop having so many kids. An atoll has a limited supply of water. It cannot support an unlimited population. Enough said.
2. Catch every drop that falls. On the ground, build small dams in any watercourses to encourage the water to soak in to the lens rather than run off to the ocean. Put water tanks under every roof. Dig “recharge wells”, which return filtered surface water to the lens in times of heavy rain. Catch the water off of the runways. In Majuro, they have put gutters on both sides of the airplane runway to catch all of the rainwater falling on the runway. It is collected and pumped into tanks. On other atolls, they let the rainwater just run off of the airstrip back into the ocean …
3. Conserve, conserve, conserve. Use seawater in place of fresh whenever possible. Use as little water as you can.
4. Make the killing of parrotfish and other beaked reef grazing fish tabu. Stop fishing them entirely. Make them protected species. The parrotfish should be the national bird of every atoll nation. I’m serious. If you call it the national bird, tourists will ask why a fish is the national bird, and you can explain to them how the parrotfish is the source of the beautiful beaches they are walking on, so they shouldn’t spear beaked reef fish or eat them. Stop killing the fish that make the very ground under your feet. The parrotfish and the other beaked reef-grazing fish are constantly building up your atoll. Every year they are providing tonnes and tonnes of fine white sand to keep your atoll afloat in turbulent times. You should be honoring and protecting them, not killing them. This is the single most important thing you can do.
5. Be very cautious regarding the use of coral as a building material. An atoll is not solid ground. It is is not a constant “thing” in the way a rock island is a thing. An atoll is an eddy, an ever-changing body constantly replenished by a (hopefully) unending river of coral sand and rubble. It is a process, wherein on one side healthy reef plus beaked coral-grazing fish plus storms provide a continuous stream of coral sand and rubble. This sand and rubble are constantly being added to the atoll, making it larger. At the same time, coral sand and rubble are constantly being eaten away, and blown away, and eroded away from the atoll. The shape of the atoll changes from season to season and from year to year. It builds up on this corner, and the sea washes away that corner.
And of course, if anything upsets that balance of sand added and sand lost, if the supply of coral sand and rubble per year starts dropping (say from reef damage or coral mining or killing parrotfish) or if the total sand and rubble loss goes up (say by heavy rains or strong winds or a change in currents) the atoll will be affected.
So if coral is necessary for building, take it sparingly, in spots. Take dead or dying coral in preference to live coral. Mine the deeps and not the shallows. Use hand tools. Leave enough healthy reef around to reseed the area with new coral. A healthy reef is the factory that annually produces the tonnes and tonnes of building material that is absolutely necessary to keep your atoll afloat. You mess with it at your peril.
6. Reduce sand loss from the atoll in as many ways as possible. This can be done with plants to stop wind erosion. Don’t introduce plants for the purpose. Encourage and transplant the plants that already grow locally. Reducing water erosion also occurs with the small dams mentioned above, which will trap sand eroded by rainfall. Don’t overlook human erosion. Every step a person takes on an atoll pushes sand downhill, closer to returning to the sea. Lay leaf mats where this is evident, wherever the path is wearing away. People wear a path, and soon it is lower than the surrounding ground. When it rains, it becomes a small watercourse. Invisibly, the water washes your precious sand into the ocean. Invisibly, the wind blows the ground out from under your feet. Protect your island. Stop it from being washed and blown away.
7. Monitor and build up the health of the reef. You and you alone are responsible for the well-being of the amazing underwater fish-tended coral factory that year after year keeps your atoll from disappearing. Coral reseeding programs done by schools have been very successful. Get the kids involved in watching the reef. Educate the people that they are the guardians of the reef. Talk to the fishermen.
8. Expand the atoll. Modern coastal engineering has shown that it is quite possible to “grow” an atoll. The key is to slow down the water as it passes by. The slower the water, the more sand builds up. Slowing the water is accomplished by building low underwater walls perpendicular to the beach. These run out until the ends are a few metres underwater. Normally this is done with a geotextile fabric tubes which are pumped full of concrete. In the atolls the similar effect can be obtained with “gabbions”, wire cages filled with blocks of dead coral. Wire all of the wire cages securely together in a triangular shape, stake them down with rebar, wait for the sand to fill in. It might be possible to do it with old tires, fastened together, with chunks of coral piled on top of them. It will likely take a few years to fill in. Here’s a before and after picture of the system in use on a beach (not an atoll), taken three years apart. Note the low height and triangular shape of the wall extending out from the beach and continuing underwater (made of 3 concrete-filled geotextile fabric tubes). This triangular shape does not attempt to stop the water currents. It just slows them down and directs them toward the beach to deposit their load of sand. Eventually, the entire area fills in with sand.
Of course to do that, you absolutely have to have a constant source of sand … like for example a healthy reef … with lots of parrotfish. That’s why I said above that the single most important thing is to protect the fish and the reef. If you have beaked fish and a healthy reef, you’ll have plenty of sand and rubble forever. If you don’t, you’re in trouble.
Coral atolls have proven over thousands of years that, if left alone, they can go up and down with any sea level rise. And if we follow some simple conservation practices, they can continue to do so and to support atoll residents. But they cannot survive an unlimited population increase, or unrestricted fishing, or overpumping the water lens, or unrestrained coral mining.
Willis Eschenbach
Honiara, Solomon Islands
*******************************
Further Reading:
On sea level rise in Honiara: Pacific Country Report Sea Level & Climate: Their Present State Solomon Islands June 2006, http://www.bom.gov.au/ntc/IDO60031/IDO60031.2006.pdf
On global sea level rise levelling off: University of Colorado at Boulder Sea Level Change, http://sealevel.colorado.edu
On Darwin’s discovery: Darwin, C., The Autobiography of Charles Darwin 1809-1882, 1887
“No other work of mine was begun in so deductive a spirit as this; for the whole theory was thought out on the west coast of S. America before I had seen a true coral reef. I had therefore only to verify and extend my views by a careful examination of living reefs. But it should be observed that I had during the two previous years been incessantly attending to the effects on the shores of S. America of the intermittent elevation of the land, together with the denudation and deposition of sediment. This necessarily led me to reflect much on the effects of subsidence, and it was easy to replace in imagination the continued deposition of sediment by the upward growth of coral. To do this was to form my theory of the formation of barrier-reefs and atolls.” (Darwin, 1887, p. 98, 99)
On the results of coral mining and changing the reef: Xue, C. (1996) Coastal Erosion And Management Of Amatuku Island, Funafuti Atoll, Tuvalu, 1996, South Pacific Applied Geoscience Commission (SOPAC), http://conf.sopac.org/virlib/TR/TR0234.pdf
On the same topic: Xue, C., Malologa, F. (1995) Coastal sedimentation and coastal management of Fongafale, Funafuti, Tuvalu, SOPAC Technical Report 221
On parrotfish creating sand: http://www.seacortez.com/fish/scaridae.html
On the cause of erosion in Tuvalu: Tuvalu Not Experiencing Increased Sea Level Rise, Willis Eschenbach, Energy & Environment, Volume 15, Number 3, 1 July 2004 , pp. 527-543
On expanding island beaches: Holmberg Technologies, http://www.erosion.com/
On the dangers of overpopulation: Just look around you …
Photograph via Walter Starck.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Thanks Willis for a timely reminder that the simple solutions to many intractable problems are often right in front of us…..but its easier to blame it on problems we cannot solve at a local scale such as sea level rise.
I have seen the same problems on many cays throughout the Indonesian Archipelago.
I suspect that not that long ago many of the inhabitants of these fragile systems actually understood all of the linkages between sand, fish, and the importance of careful management of the freshwater lens….but somehow all that knowledge has been lost.
Below is a copy of my letter to the International Herald Tribune and published on SepTember 12, 2008, however, they shortened it and deleted the reference to the coral rubble/sand that builds up on the atoll as the water rises, a process that is now impeded by permanent man-made features like road, airports and buildings.
“A SELF INFLICTED PROBLEM
In “Climate change: With millions under threat, inaction is unethical” (Views, Sept. 10) the president of the Maldives, Maumoon Abdul Gayoom, contends that the Maldives are threatened by climate change, yet he fails to acknowledge that coral islands have survived during a rise in sea levels of 120 meters since the last ice age.
Under natural conditions, coral is perfectly able to grow upwards, keeping pace with any relative rise in sea levels.
If someone has to be blamed for the eventual demise of any of the Pacific or Indian Ocean coral islands, it is the inhabitants themselves. They are the ones who are destroying the natural coral habitat by creating roads and buildings, allowing bad fishing practices and many forms of pollution. With dead coral, these islands have no natural mechanism to keep them above water. The inconvenient truth is that these islands are not sustainable under permanent human inhabitation.”
Atolls have not gone up and down in accord with changes in sea level of glacial/interglacial cycles. During most of the past 2.5 million years they have been 100 metre high eroded limestone islands exposed by the lower sea levels of glacial periods. This is attested by distinct wave cut notches along what is now the deep outer reef face of current atolls.
An example of what they may have looked like can be seen at Rennell I., Solomon Islands. Rennell is a raised atoll upthrust by tectonic buckling. The coastline is steep cliffs that were once the outer reef face of the atoll. They are now covered in dense vegetation. The old lagoon is now a freshwater lake and the lagoon patch reefs exist as numerous islands in the lake. Rennell is home to various endemic species so it has been like this for a long time without eroding away.
To see it have a look in Google Earth at 11° 43′ S, 160° 26’E.
I would think that the point is not whether the atolls themselves can survive sea level rise, clearly a 6m rise would just mean more reef and happily more fish. Whatever the local damage done by the inhabitants may be, it doesn’t contribute to sea level changes so regardless of the causes, if sea level does rise a few more meters, a lot of people will be out of real estate.
Thank you Willis and Jennifer, for an excellent presentation on how to live within your chosen environment.
Derek Smith,
“… if sea level does rise a few more meters, a lot of people will be out of real estate.”
and just how long does it take for the sea to rise a meter at the highest measured recent rate of 3.4mm/yr???? In case you are worse at math than I, that translates to .34 meters in 100 years. That rate has been adjusted down to 3.2 and may go lower. The long term rate is closer to 1.5mm.
So, one meter takes about 300 YEARS IF THE CURRENT RATE MANAGES TO REMAIN!!!!
Get over it.
The real problem with atoll dwellers, as I’ve said before, is deck space, not freeboard.
As Willis says, have fewer kids.
Temperatures and sea levels have risen and fallen in this current interglacial yet I can’t find one port around the world that has recently raised its mean sea level datum. Corpus Christi Texas did for historical reasons. I don’t think cities like New Orleans or Venice which are subsiding have even done so.
Estuarine cities like these that are forced to build levies, prevent flood silt from raising land levels and get this sinking feeling. They also sink for other reasons.
The relatively short working life of our average infrastructure means it is not an urgent problem.
Eventually if we can’t raise the bridge I’m sure we’ll lower the river or it will lower itself.
Plan B, not Plan A.
So, one meter takes about 300 YEARS IF THE CURRENT RATE MANAGES TO REMAIN!!!!
Get over it.
bad news, is the majority of your land is about 1.5 metres high, like the Maledives are.
http://en.wikipedia.org/wiki/Maldives#Geography
The Maldives holds the record for being the lowest country in the world, with a maximum natural ground level of only 2.3 m (7½ ft) with the average being only 1.5 m above sea level,
but hey, they will just get over it…
Kuhnkat, your point is well taken and is an obvious one, although it assumes a relatively static rate of sea level change. WE could experience another Younger Dryas event (however unlikely) which would leave these island nations high and dry over a very short time period. In any case I don’t need to “get over it” because I don’t really care. If people wish to live in high risk ares like the Maldives or major fault lines in Turkey etc., that’s their business.
“but hey, they will just get over it…”
Makes you wonder how they got over it for the last 3000 years.
“So, one meter takes about 300 YEARS IF THE CURRENT RATE MANAGES TO REMAIN!!!!”
I think the current rate is a bit slower than that.
http://www.dailymail.co.uk/sciencetech/article-1066712/Uncovered-lost-beach-Romans-got-toehold-Britain.html
That must have been the much touted ‘Roman Warm Period’.
Jennifer, thanks for posting my letter, much appreciated.
Derek, thanks for your comment on the Maldives. However, you seem to have missed the point. The Maldives are atolls. As such, historically they have risen when the sea level rises.
The main problem today in the Maldives is that they have mined the coral reef mercilessly to build concrete buildings. This, of course, means that the coral rubble and sand which used to rebuild the islands every day are no longer being created in adequate quantities. That means that the island stops growing.
The solution, of course, is to rebuild the reef. There are a number of successful programs around the world doing this, usually involving schoolkids. It is possible to do it, all it takes is the political will.
The Maldives are indeed in danger. However, the danger is from humans, not from sea level rise. Atolls can deal with sea level rise. They can’t deal with reef destruction and overpopulation.
Old SOD,
“The Maldives holds the record for being the lowest country in the world, with a maximum natural ground level of only 2.3 m (7½ ft) with the average being only 1.5 m above sea level,”
So, in 300 years you don’t think the coral can keep up with that smokin’ 3.4mm/yr???
Why don’t you linky us with average growth rates for coral atolls???
So, in 300 years you don’t think the coral can keep up with that smokin’ 3.4mm/yr???
Why don’t you linky us with average growth rates for coral atolls???
gratulations kuhnkat, you did qualify for the most stupid post of the week award!
people were told to get over a sea level rise of 1 metre. i decided to point out, that some epople will not get over it easily.
corals don t get into this at all. unless you assume, that the majority of those islands is build on top of growing corals.
apart from that, CO2 increase will have an effect on corals growth.
sod, please note: 1. The majority of those Maldives are indeed on top of growing corals.*
2. And yes, CO2 increase will have an effect on corals growth, it caused their growth in the first place, allows their continued growth wherever they are not mined by the people of the Maldives and elsewhere (eg PNG) for building and fishing purposes, and without it they would die.**
*”With around 2000 coral reefs, sandbars and coral outcrops, Maldives coral islands are a delight for scuba divers, snorkeling enthusiasts and people who love marine life. The coral reefs and atolls provide shelter for many species of fish, and other marine creatures. You can see numerous colorful fish swimming round the coral reefs in Maldives, while swimming or snorkeling in the clear blue water of the Indian Ocean around Maldives coral islands.
With 26 natural atolls or groups of coral islands, the Maldives, is a part of an underwater mountain range that includes the Lakshadweep Islands and the Chagos Islands. The coral reefs and atolls that make up these islands, have grown on and around the peaks of this underwater mountain range”. Thanks to Google, http://www.tourisminmaldives.com
**”Coral is a marine polyp that lives in large colonies. Its hard outer shell forms the structure of the coral reef. The live polyp within keeps adding to the reef as it keeps building its shell” (from CaCO3 etc) (ibid.).
Tim, what you write is simply stupid!
sod, please note: 1. The majority of those Maldives are indeed on top of growing corals.*
the corals are growing AROUND the island. not beneath it. you are simply wrong!
2. And yes, CO2 increase will have an effect on corals growth, it caused their growth in the first place, allows their continued growth
why don t you simply test this? just fill your aquarium or that of a friend with one of the low ph mineral waters. (propel fitness water?)
http://www.phconnection.com/Bottled_Water_pH_List.html
the plants will love it and the fish will adapt soon.
Sod knows more about the Maldives than themselves! Sure, new corals are growing around the isalnds made up of old growth corals, or would but for the idiot President busy digging them up, and when alowed will of course produce an admirable sea wall. As to his second point, what is the chemical composition of corals? Get back to Darwin mate!
This was a good post that was degraded by anti-human bias. It is not the number of people that impacts on the environment but, rather, what they do. If residents of coral atolls sourced their water from sources other than ground water there would be little impact on the lens. There are a number of alternatives in practice elsewhere.
If houses were constructed on stilts over the lagoon (as is common in the Philippines, Kalimantan and Suluwesi) then rainwater could be captured in tanks with no adverse impact on ground water. Indeed, the other great killer of coral, fresh water, would actually be reduced. Rainfall on the land area of most coral atolls is far in excess of human needs and the area of sheltered lagoon is far in excess of land area.
Another approach would be to enclose an existing area of salt water lagoon with a suitable bund, pump the sea water out, seal it with dam liner, and then allow the rain to fill it with fresh water. It would not alter the hydrology of the existing fresh water lens and provide a large, cheap storage of a rainwater resource that is currently not even recognised as being available.
Another option would be to use the same membrane but with floating sides so the volume of fresh water inside could vary without any interaction with the lagoon bed at all. A clear plastic membrane would even allow sunlight to pass through the fresh water onto the lagoon bed below with minimal impact on the ecology of that small area of the larger lagoon ecosystem.
The intelligent choice would be “all of the above and more”.
It is really quite intellectually lazy to identify a problem created by an existing human behaviour but instead of finding a behaviour modification or other technical solution that would fix the problem, to simply demand fewer humans. It is a triple A rated cop-out. And it invites the response that if humans are the problem then lets start by eliminating the least imaginative ones, ie, yourself.
It is interesting to note, in light of the recent tragedy of the Samoan tsunami, that houses on stilts in the lagoon would fare much better than those on the concrete slabs on the shoreline. The real damage by wave action comes when it’s lower half (below water line) meets solid land. It lifts and the rolling action becomes more violent. Houses on stilts would need to be a few metres above sea level to avoid storm action etc. And when the stilts extend a few metres below sea level to the lagoon floor it leaves a lot more room for all but the largest tsunamis to pass underneath. Providing solid barriers, like house walls, against overwhelming natural forces has never been clever practise.
There are reports that some of the tourist facilities on stilts over the lagoon did not fare well in southern Samoa. But these facilities have been designed to maximise proximity to water and appear to have compromised structural integrity, and building materials for aesthetic appeal. They are less likely to make that mistake again.
At present, some 24 hours after the event, there is still no word from the low atolls of Tokelau 450km north of Samoa, maximum altitude 5m above SL.
You may find this interesting,
Who is Willis Eschenbach?
http://www.populartechnology.net/2013/10/who-is-willis-eschenbach.html
As of 2012 Mr. Eschenbach has been employed as a House Carpenter.
He is not a “computer modeler”, he is not an “engineer” and he is certainly not a “scientist” (despite all ridiculous claims to the contrary).
“A final question, one asked on Judith Curry’s blog a year ago by a real scientist, Willis Eschenbach…”