GLOBAL WARMING AND ITS IMPACT ON HAWAII’S CORAL REEFS
by Bill Irwin, November 2014
So far Hawaii has been lucky in that we have not had any major disasters caused by Global Warming. We have seen a shift in weather patterns, more frequent flash floods, some beach erosion, and a declining fish catch. Our luck will be running out in the near future for Global Warming is affecting the oceans in ways that will impact the marine life that surrounds our islands. Our coral reefs will become an endangered species unless we do something very soon to reverse the buildup of CO2 in our atmosphere, for CO2 is changing the chemistry of the oceans and is causing our world to warm up both of which adversely affect many forms of marine life, coral more than most.
Our coral reefs are very important to Hawaii. They provide a habitat that is home to a wide variety of marine organisms as anyone who has gone snorkeling in Hawaii can testify to. The reefs provide a source of food which has long been the main source of subsistence for the Hawaiian people. They provide recreation for our people, and businesses that provide that sort of recreation to our visitors are a $304 million dollar a year source of income and jobs. More than half of our visitors go snorkeling at least one time during their visit – our beautiful reefs are one of the draws that make our multi-billion dollar tourist industry work. The reefs also provide protection from the full intensity of ocean waves and currents. Without the reefs the beaches would be more susceptible to erosion and damage to shore side homes and property. The protection they offer is worth millions of dollars every year. The direct contribution of coral reefs to our Hawaiian economy is around $364 million a year. And of course, that beautiful white sand on our beaches is made from coral. Coral, along with some species of marine algae, also produce a chemical (dimethylsulphoniopropionate) which is responsible for creating the unique scent of the ocean and also functions as a seed for cloud formation. Of course clouds bring us rain and reflect a portion of sun light back into space which helps prevent global warming.
CO2 is directly changing the chemistry of the oceans, CO2 combines with water to form carbonic acid and since it is an acid it causes the pH to fall, a process called ocean acidification. Carbonic acid is not a strong acid nor is it much a threat to health as it is in all your soda drinks and gives them a more tart taste. The main problem with increasing the pH of the oceans is that it makes calcium carbonate much less soluble in sea water. There is no shortage of calcium carbonate as it is the main ingredient in white sand and is the main structural material for forming coral and marine organisms that form a hard shell such as oysters and mussels. Calcium carbonate can also enter the oceans from runoff from the land. A mere 0.1 point decline in pH has led to a 26% increase in hydrogen ions, the active part of acids. CO2 in the atmosphere has now reached 400 parts per million which is 100 ppm higher than at anytime in the last 740,000 years. At the current rate of emissions increases, which is 2.07 ppm per year, we will reach 500 ppm of CO2 in the atmosphere by 2063 and if you factor in the rate of increase we could reach that level by 2050. At 500ppm reefs are no longer able to maintain themselves as the rate of calcium uptake and coral growth is less than the normal destructive forces that coral face, reefs will begin to disappear. Presently it is estimated that world-wide reefs are declining about 2% per year. Some places in the Great Barrier Reef of Australia have seen a 20% decline in the past 16 years.
Coral are not the only species that will be affected by low carbonate levels caused by ocean acidification. Crabs and other shellfish make their shells strong by calcium carbonate deposits making it difficult for baby crabs to build a shell. Laboratory studies have shown that the Alaskan crab fishery is in danger and within the next decade may no longer be feasible. Another important group of sea creatures that is being affected are sea butterflies, also known as Pteropods. Pteropods are small marine plankton that have a shell formed from calcium carbonate and grow in great abundance in the southern oceans; they are adversely affected by CO2 at 450ppm. They are important in that when they die they sink to the bottom of the sea floor where they form vast calcium carbonate deposits which are important to the world eco-system and its carbon cycle because this is one of the main means of carbon sequestration.
Another problem our coral reefs face is the warming of the oceans also caused by our over-production of CO2. Coral have two methods of feeding, they can capture small planktonic prey with their tentacles, and they have an algae growing amongst their tissues which provide them with carbohydrates. The coral/algae relationship is a symbiotic relationship in that both receive benefits from the relationship, the coral receive the majority of their nourishment from the algae and the algae receive a safe place to live, CO2 which they need for their photosynthesis activity, and some fertilizer in the form of urea which most animals produce as a waste. The algae are very sensitive to sea temperature and UV radiation from the sun. They don’t like warm water, if sea surface water temperatures get into the 84-86 degree range this can cause the algae to die off. As the algae start to die the coral expel them from their tissues and since the coral tissue are colorless the white structure of the calcium carbonate coral show through. This whitening of the coral is called ‘coral bleaching’. With the loss of their major food supplier the coral begin to weaken and become susceptible to diseases that affect coral which is the major cause of coral death in coral bleaching events. The coral/algae relationship is so sensitive to rising temperatures that even a 1-2 degree temporary rise above the normal seasonal temperature can cause some coral bleaching; the surface temperature doesn’t even have to reach the 84-86° level.
Hawaiian reefs are in decline, a few locations that are more removed from human contact such as Molokini are holding their own. One of the worst areas are the reefs along Maui’s west coast, these reefs saw 25% loss in coral cover in 12 years from 1994-2006. Perhaps the hardest hit was Maalaea Reef which was about 50-75% cover in 1993 then declined to only 8% cover by 2006. The principal causes of Maui’s problems are from over-development of the nearby shore which causes excessive run-off which brings with it sediment which can cause the death of coral and nutrient enrichment from fertilizer and sewerage discharge which cause the invasive macroalgae to bloom in great numbers. Over fishing on the reefs has also reduced the numbers of herbivore fishes which also allows for the overgrowth of the macroalgae, something the coral can’t handle so their numbers decline. Reefs that are closed to fishing show much less invasive macroalgae. The same problems of reef decline due to development are beginning to show in the reefs on the west coast of the Big Island and are only going to get worse unless more care is taken.
Maalaea Reef West Maui: Extensive coral bleaching with invasive macroalgae
The health of the reefs on the Big Island, which are mostly located on the Kona coast, is a mixed story. Some are doing well, others are showing marked declines; reefs south of Keahole Point are for the most part holding their own or even expanding, of the reefs north of Keohole Point 7 of 9 reefs are showing significant declines. The further south you go the healthier the reefs. The area north of Keahole Point is the area of West Hawaii where the majority of hotels, golf courses, and housing development is taking place and the sediment and fertilizer run-off from this activity is causing a problem for coral health. South of Keohole point is one of the least populated areas of Hawaii and most of the population is more inland from the coast. The reefs off Puako seem to have the most serious problems. In the 1970’s coral cover was at 80%, then declined to around 50% cover by 2003, by 2011 it was down to only 34% cover, a loss of over 50% of the coral since the 70’s.
The waters off the Kona coast are also warming up. Mean water temperatures for west Hawaii waters was 79.5° in 2012. In the period 1999-2005 we saw a rapid rise in temperature of 1.8-2.7° following a period of El Niño warming of the Central Pacific, from 2006- 2011 saw a decline back to normal levels, 2012 saw an increase of 0.39°. Several reefs got into the danger zone of 82° during the late summer of 2004 and 2005. In checking the temperature at Kawaihae in Oct. 2013 was showing 85° – the point of wide-scale coral bleaching. I think the temperature was inside the harbor area so was elevated and is not typical for the surrounding areas but does show that our waters can get to a temperature that will no longer support the growth of coral. The long term trend shows warming ocean waters, we have now reached the point that another El Niño period could cause the temperature of our waters to rise into the zone that would cause large scale die off of our coral. In other words, we are at the tipping point – further rise in ocean temperatures or increases in CO2 could cost us the loss of our coral reefs – something we cannot let happen.
Global warming is also causing another problem that will greatly affect Hawaii; the rising temperature is causing glaciers and ice caps at the poles to melt causing the sea level to rise. If the same trend continues we could see a 39 inch rise in sea level by 2100 which would be a tremendous problem for our coastal cities, Honolulu in particular. Since most of our tourist infrastructure of hotels, beaches, and shopping are located on the ocean front most all of this will have to be relocated and rebuilt which is going to be very expensive. An expense our children and grand-children will have to bear. See the link on the projected sea level rise for some maps of what the future of Honolulu might look like.
What we need to do
Hawaii’s reefs face problems from two fronts. The global warming problem caused by too much reliance on fossil fuels producing too much CO2 is a global problem. We all contributed to this problem and one person cannot turn this around, we all must do our part to cut our reliance on fossil fuels. The other problem is local in origin and that is the run-off of pollutants, fertilizer and sediments from the land. We alone are responsible for that and are the only ones who can correct that problem. Global warming is a serious problem and is a threat to our reefs and fishing, we cannot afford to let this happen. Start by encouraging our law-makers to take stronger action to not only cut back on CO2 but try to eliminate it. Let them know that you know it will be a difficult process but that you will support them in this effort and that you want to see a faster conversion to alternate energy sources for Hawaii. Individually we each have to look at our life style and try to be more energy efficient. The good news is that cutting back on our CO2 footprint will save us money and enrich our lives; it is even a good investment. A solar hot water heater should be the first step as you can save on your electric bill and increase the value of your home, if you are a little bit handy with plumbing you can even make your own. The same goes for adding solar panels to your house, the savings on the electric bill and tax credits will more than pay for the system and it is an investment that will make your home more valuable when the time comes to sell. The biggest polluter of our air and oceans is you car. The electric car is the future of our transportation, might as well move to the future as soon as you can – don’t buy another new, gas powered car! If you just have to buy something now and are not ready to go electric then buy a used gas hog – don’t take the responsibility of putting another gas-hog on the road. If you buy a solar charging station for your electric car you can drive the rest of your life for free. No more gas bills for a lifetime, you can save a lot of money there and save our reefs at the same time!
The other problem of local, land based pollution entering the ocean which is causing a real problem for our reefs as the decline of west coast Maui reefs and the reefs north of Keahole Point on the Big Island shows. Soil sediments cover the coral and literally smother them in a mud coating, fertilizers encourage the growth of macroalgae which coral can’t cope with so decline (see the photo of Maalaea Reef above for the effect of macroalgae on coral), and pollutants and the many chemicals we use, many are out-right poisons and none are good for the health of reefs or humans. If you live within a mile or two of the ocean stop using fertilizers on your lawns and golf courses, grass doesn’t need that much help to grow in Hawaii and the fertilizers are causing a real problem. Construction causes a problem with sediments as the disturbed soil is easily washed away and into the ocean. Now that we are seeing increased rain and much more flash-flooding the problem of sediments entering the ocean is even more of a problem. If you are doing a construction project try to do as the highway builders are doing and put run-off barriers around your project to block the flow of run-off from your project and try to get the land covered with grass, buildings, or parking lot as soon as you can – anything to stop the loss of soil from your property. All the other pollutants you are using please dispose of them properly, when you live on an island everything you dump on the ground will eventually make its way into the ocean. The county has programs to take in your hazardous chemicals and dispose of them properly – please take advantage of this service.
We are now at the tipping point where further increases in CO2 will cause the loss of our coral reefs, if we start taking actions to reduce our reliance on carbon based energy now we can turn it around. We also need to look at how our actions on land are affecting coral and fish populations and take strong actions to stop that. As it stands today, us folks living in Hawaii are the greatest danger to the health of our ocean eco-systems and we are the only ones that can save them.
In addition, I would suggest that you study the topic of sustainable agriculture even if you are not interested in farming or gardening. Learn the principals of a sustainable lifestyle and apply that learning to your life, your job, and your work – if we are to have any kind of life for future generations building a sustainable economy, agriculture, and life style is the only solution that will actually work.
References used in the preparation of this report:
All about coral: http://en.wikipedia.org/wiki/Coral
Coral Reef Bleaching: http://www.marinebiology.org/coralbleaching.htm
Coral makes clouds to keep climate sweet: http://www.universityworldnews.com/article.php?story=20131107133611463
Coral Reefs Under Rapid Climate Change and Ocean Acidification: http://www.geneseo.edu/~bosch/Hoegh-Guldberg.pdf
The economic value of coral reefs to Hawaii – on page 9 of: http://coralreef.noaa.gov/Library/Publications/valuesummaryreport.pdf
Decline of West Maui reefs: http://state.hi.us/dlnr/dar/pubs/MauiReefDeclines.pdf
The State of Coral Reef Ecosystems of the Main Hawaiian Islands: http://ccma.nos.noaa.gov/ecosystems/coralreef/coral_report_2005/MHI_Ch9_C.pdf
Long-Term Monitoring of Coral Reefs in the Main Hawaiian Islands (primarily covers the West, Big Island coast, good survey of trends in fish and coral populations): http://state.hi.us/dlnr/dar/pubs/NOAA_2013_WHi_%20Mon_%20Rep.pdf
Ocean Apocalypse – A video presentation of the many problems facing the oceans world-wide. Kind of a long and depressing presentation but if you care about the future of our oceans and Hawaii’s reefs it is recommended viewing. https://www.youtube.com/watch?v=2zMN3dTvrwY
Alaska crab fishery in danger: http://apps.seattletimes.com/reports/sea-change/2013/sep/11/alaska-crab-industry/
Sea Butterflies (Pteropods) are the oceans “Canary in the Coal Mine: http://blogs.smithsonianmag.com/artscience/2013/05/amazing-sea-butterflies-are-the-oceans-canary-in-the-coal-mine/
Southern Ocean acidification, A tipping point at 450-ppm atmospheric CO2: http://www.pnas.org/content/105/48/18860.short
Sea level rise and effect on Hawaii: http://archives.starbulletin.com/2007/09/23/news/story01.html
Regional Decline of Coral Cover in the Indo-Pacific: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000711
Deoxygenation in warming oceans: http://geology.gsapubs.org/content/40/7/671.full
Hawaii’s Climate Change and Marine Disease Local Action Strategy: http://coralreef.noaa.gov/aboutcrcp/strategy/reprioritization/wgroups/resources/climate/resources/hi_cc_las.pdf
On Sustainable Agriculture http://www.sustainable-ag.ncsu.edu/onsustaibableag.htm , http://en.wikipedia.org/wiki/Sustainable_agriculture
A look at the personal economics of going solar to meet your energy needs: http://www.greenpowervideos.com/economics.htm
Hawaii– Incentives/Policies for renewables and energy efficiency: http://www.dsireusa.org/incentives/index.cfm?re=0&ee=0&spv=0&st=0&srp=1&state=HI