LONDON , England ( CNN ) -- The world has lost almost one-fifth of its coral reefs according a new report released by the International Union for Conservation of Nature ( IUCN ) . Coral reefs could be wiped out in 30-40 years according to a new report . Compiled by the Global Coral Reef Monitoring Network , the report has brought together the work of researchers from 15 countries with data stretching back 20 years . It 's not just climate change -- which raises ocean temperatures and increases seawater acidification -- which is damaging reefs . In some parts of the world overfishing , pollution and invasive species are proving equally harmful . Scientists are warning that reef destruction will have alarming consequences for around 500 million people who rely on coral reefs for their livelihood . Left unchecked , remaining reefs could be completely wiped out by 2050 , the report says . Professor Olof Linden from the World Maritime University in Malmo , Sweden , told CNN : `` We see a great and imminent threat of more reefs being lost . '' Speaking from the U.N . Climate Conference in Poznan , Poland , Professor Linden said that the 19 percent figure is an average . `` For many developing countries like Sri Lanka and countries in East Africa the percentage of damage is much worse . Sometimes three times as high in some places , '' he said . `` In these areas we have local effects like dynamite fishing and other destructive fishing techniques combined the threat of coral mining , unmanaged tourism and all kinds of pollution from agriculture . '' But overall the biggest threat to reef survival is climate change . `` The most destructive climate event to impact the coral reefs so far , '' said Linden , `` was the 1998 El Nino which caused major coral bleaching and disrupted ecosystems all over the planet . '' iReport.com : What little things are you doing to save the planet ? Scientists say reefs have recovered somewhat from those bleaching events . But the Indian Ocean tsunami in 2004 , coupled with coral disease and human effects , have slowed their recuperation . Coral reefs not only provide an income and food for those who live near them , but are also effective natural barriers against storm surges . Despite the report 's pessimism , researchers see some encouraging signs . Forty-five percent of the world 's reefs are currently in good health and the hope remains that damaged reefs can recover and adjust to the changing conditions . `` We must focus on helping corals to adapt to climate change and on diverting people away from destructive practices such as overfishing , '' Linden said .
The world has lost almost a fifth of its coral reefs , states a new report . Climate change , overfishing and coral mining all are contributing to destruction . In some parts of Indian Ocean up to 90 percent of reef life has died .