Global Warming Effects Around the World

Bolinao, Philippines

Top Impact

Ecosystems (Salt water)

Other Impacts

Oceans (Ocean chemistry)

Temperature (Ocean)

Dead corals litter a beach in Bolinao, Philippines

Dead corals litter a beach in Bolinao, Philippines. Global warming—which causes ocean acidification and contributes to coral bleaching—is compounding the threats posed by destructive fishing techniques, coastal development, forest destruction, and aquaculture. These stresses are putting hundreds of coral and fish species and millions of people dependent on Filipino reefs at risk.1

Key Facts

The coral reefs of the Philippines—the second-largest in Southeast Asia—support hundreds of species of corals and fish.2,3,4,5 Already endangered by direct human activity, these reefs are under additional pressure from global warming.2,3,6,18

  • The Philippines lies within the Coral Triangle, which includes more than 75 percent of all coral species and 35 percent of the world's coral reefs.5 The region's reefs are worth more than U.S.$2 billion annually because of the fishing, tourism, and storm protection they provide.5
  • Some 98 percent of Philippine reefs are classified as threatened, with 70 percent at high or very high risk.2,5 Unsustainable practices such as blast fishing and cyanide fishing are thought to be the largest contributors to reef degradation.2,6
  • Climate change is increasing both the temperature and the acidity of the ocean. Rising temperatures increase the risk of coral bleaching. When the Philippines suffered its first mass coral bleaching at the end of the twentieth century, 80 percent of the corals around Bolinao were affected. If we continue on a path of high heat-trapping emissions, acidity levels could begin to deprive corals of the ingredients they need to build skeletons by mid-century.2,3,8,12,18


The coral reefs of the Philippines are the second-largest in Southeast Asia, covering 10,000 square miles (26,000 square kilometers).5 The reefs support extraordinary biodiversity, including more than 400 species of hard coral—12 of which are unique to the area—and more than 900 species of reef fish.2,3,4

Filipino residents depend on these tremendous natural resources for fishing, tourism, and storm protection, valued at more than U.S.$2 billion annually.5

However, human activity—including fishing, coastal development, farming, and fish farming—also poses a growing threat to Philippine coral reefs.6 Environmentally destructive fishing practices are the largest contributor to reef degradation.6 Although techniques such as blast fishing and poison fishing are banned, enforcement is lacking.2 Fishers often use cyanide to stun fish, making them easier to catch. However, when used repeatedly, this technique can kill corals.2

More than 80 percent of the original tropical forests and mangroves in the Philippines have been cleared, with some converted to fish ponds.7 These changes allow more sediment and nutrients to flow onto and smother the reefs.6,7 Destruction of mangroves also leaves coastal areas vulnerable to storms, waves, and erosion.8,9,10,11 (For more information on mangroves, see hotspot on Kolkata, India.)

Nearly two-fifths of Southeast Asia's coral reefs have already been destroyed.8 Today only 10 percent of Philippine reefs are considered healthy or very healthy.5

Global Warming Worsens Existing Threats

The region's reefs cannot afford two additional major stresses posed by climate change. These include further increases in ocean temperatures, which can trigger coral bleaching, and ocean acidification, which at critical thresholds makes it difficult for corals to build shells and skeletons.8,12

Corals' spectacular coloration comes from symbiotic algae, which also nourish them.13 When rising ocean temperatures or ultraviolet light stress the corals, they lose their colorful algae, leaving only transparent tissue covering their white calcium-carbonate skeletons.14 If the stresses are sustained, the corals die.13,15 Even small increases in water temperature can cause coral bleaching.

Since 1950, global mean sea surface temperatures have risen roughly 1° F (0.6° C).16 The intensity and frequency of coral bleaching has increased significantly over the past 30 years, causing death or severe damage to one-third of the world's corals.13,17

The Philippines first suffered mass coral bleaching in 1998-99.3 Reefs off northern Luzon, west Palawan, the Visayas, and parts of Mindanao were affected. The worst bleaching—which affected 80 percent of corals—occurred around Bolinao.3,18

What the Future Holds

Continued acidification of the ocean as it absorbs our carbon emissions poses another danger to corals and other sea animals that need calcium carbonate to build shells or skeletons.13,19,20 Scientists warn of a threshold point where the ocean becomes so acidic that calcium carbonate—in the mineral form that corals use—is unavailable to corals for building reefs.13,21,19,22 Studies show that a doubling of atmospheric carbon dioxide would reduce coral calcification more than 30 percent.13,23

Loss of biodiversity in the Coral Triangle is another expected impact of global warming. As corals die off, the number of species supported by the reef declines, and local extinctions can occur.13,24



  1. Photograph courtesy of Armel Madsen. Pebbles and dead corals littering the beach in Bolinao, Pangasinan, Philippines. Accessed 30 Nov 2010 at photos/ bibedoggie/ 672087332/ in/ set-72157600155722479/
  2. Burke, L., E. Selig, and M. Spalding. 2002. Reefs at risk in Southeast Asia. World Resources Institute. Online at rrseasia_full.pdf. Accessed May 24, 2010.
  3. Licuanan, W.Y., and E.D. Gomez. 2000. Philippine coral reefs, reef fishes, and associated fisheries: Status and recommendations to improve their management. In: Status of coral reefs of the world: 2000. Edited by C. Wilkinson. Townsville, Queensland: Australian Institute of Marine Science.
  4. Wilkinson, C. 2000. Status of coral reefs of the world, 2000. Townsville, Queensland: Australian Institute of Marine Science.
  5. Wilkinson, C. 2008. Status of coral reefs of the world, 2008. Townsville, Queensland, Australia: Global Coral Reef Monitoring Network, and Reef and Rainforest Research Centre.
  6. Chou Loke Ming. 1998. Status of Southeast Asian coral reefs. In: Status of coral reefs of the world, 1998. Edited by C. Wilkinson. Townsville, Queensland: Australian Institute of Marine Science.
  7. Department of Environment and Natural Resources, et al. 2001. International coral reef initiative Country report: Philippines. Paper presented at the International Coral Reef Initiative Regional Workshop for East Asia, Cebu, Philippines, April 2-4, p. 10.
  8. Cruz, R.V., H. Harasawa, M. Lal, S. Wu, Y. Anokhin, B. Punsalmaa, Y. Honda, M. Jafari, C. Li, and N. Huu Ninh. 2007. Asia. In: Climate change 2007: Impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson. Cambridge University Press, pp. 469-506.
  9. Mazda Y., M. Magi, M. Kogo, and P.N. Hong. 1997. Mangroves as a coastal protection from waves in the Tong King Delta, Vietnam. Mangroves and Salt Marshes 1: 127-135.
  10. Mazda Y., M. Magi, Y. Ikeda, T. Kurokawa, and T. Asano. 2006. Wave reduction in a mangrove forest dominated by Sonneratia sp. Wetlands Ecology and Management 14: 365-378.
  11. Vermaat, J., and U. Thampanya. 2006. Mangroves mitigate tsunami damage: A further response. Estuarine, Coastal and Shelf Science 69:1-3.
  12. Nicholls, R.J., P.P. Wong, V.R. Burkett, J.O. Codignotto, J.E. Hay, R.F. McLean, S. Ragoonaden, and C.D. Woodroffe. 2007. Coastal systems and low-lying areas. In: Climate change 2007: Impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson. Cambridge University Press, pp. 315-356.
  13. U.S. Global Change Research Program. 2009. Global climate change impacts in the United States. Edited by T.R. Karl, J.M. Melillo, and T.C. Peterson. Cambridge University Press.
  14. Hoegh-Guldberg, O. 2005. Low coral cover in a high-CO2 world. Journal of Geophysical Research 110. doi:10.1029/2004JC002528.
  15. Donner, S.D., W.J. Skirving, C.M. Little, M. Oppenheimer, and O. Hoegh-Guldberg. 2005. Global assessment of coral bleaching and required rates of adaptation under climate change. Global Change Biology 11(12):2251-2265.
  16. Bindoff, N.L., J. Willebrand, V. Artale, A, Cazenave, J. Gregory, S. Gulev, K. Hanawa, C. Le Quéré, S. Levitus, Y. Nojiri, C.K. Shum, L.D. Talley, and A. Unnikrishnan. 2007. Observations: Oceanic climate change and sea level. In: Climate change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller. Cambridge University Press, pp. 386-432.
  17. Janetos, A., L. Hansen, D. Inouye, B.P. Kelly, L. Meyerson, B. Peterson, and R. Shaw. 2008. Biodiversity. In: The effects of climate change on agriculture, land resources, water resources, and biodiversity in the United States. Edited by P. Backlund, A. Janetos, D. Schimel, J. Hatfield, K. Boote, P. Fay, L. Hahn, C. Izaurralde, B.A. Kimball, T. Mader, J. Morgan, D. Ort, W. Polley, A. Thomson, D. Wolfe, M.G. Ryan, S.R. Archer, R. Birdsey, C. Dahm, L. Heath, J. Hicke, D. Hollinger, T. Huxman, G. Okin, R. Oren, J. Randerson, W. Schlesinger, D. Lettenmaier, D. Major, L. Poff, S. Running, L. Hansen, D. Inouye, B.P. Kelly, L. Meyerson, B. Peterson, and R. Shaw. Synthesis and assessment product 4.3. Washington, DC: U.S. Department of Agriculture, pp. 151-181.
  18. Divinagracia, M.F.B. 2000. Extent and degree of coral bleaching in selected reefs in Central Visayas, Philippines.Thesis for master of science in biology. Dumaguete, Philippines: Siliman University.
  19. Clarke, L., J. Edmonds, H. Jacoby, H. Pitcher, J. Reilly, and R. Richels. 2007. Scenarios of greenhouse gas emissions and atmospheric concentrations. Sub-report 2.1A of synthesis and assessment product 2.1. Washington, DC: U.S. Department of Energy, Office of Biological and Environmental Research.
  20. Orr, J.C., V.J. Fabry, O. Aumont, L. Bopp, S.C. Doney, R.A. Feely, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, R.M. Key, K. Lindsay, E. Maier-Reimer, R. Matear, P. Monfray, A. Mouchet, R.G. Najjar, G.-K. Plattner, K.B. Rodgers, C.L. Sabine, J.L. Sarmiento, R. Schlitzer, R.D. Slater, I.J. Totterdell, M.-F. Weirig, Y. Yamanaka, and A. Yool. 2005. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature 437 (7059):681-686.
  21. Monaco declaration. 2009. Developed at the Second International Symposium on the Ocean in a High-CO2 World, Monaco, 6-9 October 2008. Online at oanet/ Symposium2008/ MonacoDeclaration.pdf.
  22. Feely, R.A., C.L. Sabine, J.M. Hernandez-Ayon, D. Ianson, and B. Hales. 2008. Evidence for upwelling of corrosive "acidified" water onto the continental shelf. Science 320 (5882):1490-1492.
  23. Royal Society. 2005. Ocean acidification due to increasing atmospheric carbon dioxide. Policy document 12/05. London.
  24. Graham, N.A.J., S.K. Wilson, S. Jennings, N.V.C. Polunin, J.P. Bijoux, and J. Robinson. 2006. Dynamic fragility of oceanic coral reef ecosystems. Proceedings of the National Academy of Sciences 103 (22):8425-8429.
Climate Hot Spots
Australia & New Zealand
Latin America
North America
Polar Regions
Small Islands
Key to top impacts color code