Coral Reefs

Coral reefs are an ecosystem that have the second biggest biodiversity in the world and have been described as the rainforests of the ocean. For years they have been threatened by man. Physical destruction from boats, fishing and pollution. Now their biggest threat may be from climate change.

15% of the world’s reefs have already been lost and 30% may die in the next 30 years.

Coral reefs are a complex ecosystem – tiny sea anemone-like polyps build coral reefs by secreting brittle, limestone skeletons. Algae support the polyps by converting sunlight and carbondioxide into sugars that feed them; the polyps, in turn ooze waste products that nurture the algae.

Coral grows near the surface of the water. Coral forming polyps.

A rise of sea temperatures by as little as 1 or 2°C can cause a major coral bleaching event where the algae, which feed the coral growing polyps, die. A rise of 3 or 4°C will mean that the algae never returns.

Rises in dissolved, acidic, carbon dioxide in the sea water also means that the polyps are unable to form coral through calcification. Coral is made from calcium carbonate which dissolves in acid. Decomposing algae from bleaching events, will increase dissolved carbon dioxide in the water.

Warmer sea water also leaves the reefs more vulnerable to pollutants and diseases.

Australia’s Great Barrier Reef is at the brink of a major bleaching event at the moment with sea water up to 2°C warmer than normal. This will be the third bleaching in six years, increasing the risk that the reef may never recover.

If we lose our coral reefs we lose not only the wildlife that lives there, income from tourism, but also protection for the coasts from the increased number of storms expected from climate change. This was shown after the Boxing Day earthquake off Aceh, Indonesia caused the devastating Tsunami.

Islands protected by unspoilt coral reefs like Surin Island and the Maldives appeared to have suffered less damage and suffered less casualties. The reefs absorbed most of the power of the giant waves.

Rising Sea Levels – The World

Global average sea levels have risen by 10 – 25 cms over the past 100 years. In the next 100 years they could rise by another 50 cms (maybe more).

This is due, not only to melting polar ice and glaciers adding extra water to the seas, but to the sea water expanding as it heats up.

This could mean total disaster for many islands and coastal areas, especially river delta areas.

A sea level rise of 1 metre could mean estimate land losses of 0.05% in Uruguay, 1% in Egypt, 6% in the Netherlands, 17.5% in Bangladesh and up to 80% for Atoll Majuro in the Marshall Islands.

Bangladesh consists mainly of low lying deltas – rising sea levels, together with increased tropical storms will see millions of people having to flee their homes.

In the Pacific Ocean there many tiny islands that are at risk of being totally covered by the sea. Two islands: Tebua Tarawa and Abanuea (the beach which is long lasting) in the Kiribati group of islands, have already been covered by sea water.

On the right, Tepuka Savilivili is another islet that has been destroyed by rising seas, which washed off the coconut trees and other vegetation.

Tuvalu, a group of nine coral atolls has started to evacuate is population to New Zealand. 75 people are moving annually. This picture shows the centre of the island flooding during a very high tide.

In river delta areas are richly fertile agricultural areas and many large cities. The impact on populations and economies could be very large indeed.

In other areas coastal erosion could increase, and salty sea water could spoil underground aquifers of freshwater that local populations rely on for drinking.

Melting polar ice could also affect ocean water movement. It is thought that the Gulf Stream could be diverted further south by the addition of cold water from the north, changing much of western Europe’s weather patterns.

Even if you live safely on a hill, rising sea levels will affect you. So many large populations of people live in areas at risk of permanent flooding, you will either be paying for their protection, or for their resettlement.