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WARMING OCEANS The effects of climate change can already be observed as the world's oceans are getting warmer. The five warmest years in history have all been recorded in the last two decades, and there has been an unprecedented increase in the number of coral bleaching events during this period. Bleaching has most commonly been reported in the tropical Eastern Pacific, especially affecting the reefs of Costa Rica, Panama, Colombia, and the Galapagos Islands. The worst bleaching episodes have coincided with a strange we ather event known as El Niño. El Niños are periodic natural weather cycles that originate in the Pacific but can cause water temperatures to rise and extreme weather (hurricanes, droughts, and floods) around the world. The worst coral bleaching has happened when the effects of an El Niño have been superimposed on the recent global warming caused by greenhouse gas pollution. Even now, in 1997, coral bleaching is being observed in many places, including the WWF supported Saba Islands Marine P ark in the Netherland's Antilles. Other reefs in the Caribbean, for instance, the Bonaire Marine Park, have still not recovered from bleaching in 1994. WWF scientists are concerned that other reefs where conservation efforts are underway with local commun ities may also be threatened. These include Tanzania's Mafia Island and Japan's Shiraho reef. Warming waters aren't the only threats posed to coral reefs by climate change. Many scientists believe that global warming will herald a new era of extreme and unpredictable weather. Tropical storms may increase and so too would the consequent physical da mage to coral reefs. Hurricanes Hugo and Marilyn hit the U.S.Virgin Islands National Park in 1989 and 1995 respectively and did massive damage to coral ecosystems. Things could look bleak for many reefs around the world. Another effect of climate change will be heavier and more abundant rainfall in some areas. Heavy rainstorms cause serious soil erosion in coastal areas and on islands that can result in damage to reefs. Sediment, freshwater and agricultural chemicals floo d off the land, down rivers, and out into the sea, inundating the fringing coral reefs. One such flood plume from Australia's Fitzroy River caused mass coral deaths on the Keppel Island reefs. Indeed, increased damage to reefs in this way may be one of the most rapid and alarming effects that climate change will have on corals. Rising sea levels caused by global warming could be an additional problem for some reefs. The governments of small island nations, such as; the Maldives in the Indian Ocean and Kiribati and Tuvalu in the Pacific have been calling for international action to slow climate change. Their nations are based entirely on coral atolls no more than two meters above sea level; therefore, rising water levels could have serious impacts.
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