CLIMATE CHANGE

The climate of the Earth is always changing. In the past it has altered as a result of natural causes. Nowadays, however, the term climate change is generally used when referring to changes in our climate which have been identified since the early part of the 1900's. The changes we've seen over recent years and those which are predicted over the next 80 years are thought to be mainly as a result of human behaviour rather than due to natural changes in the atmosphere.

It is difficult to predict what the long-term effects of global climate change will have on the marine environment but plankton, and phytoplankton, which are fundamental to the marine food chain, become less abundant when seawater warms. There is also strong evidence that the Antarctic ice shelves are receding at an alarming rate, and we do know that this could be devastating for some species.

  

The greenhouse effect could also change the pattern of heat distribution of the Earth's surface, which will alter ocean circulation patterns, precipitation patterns, and storm tracks. As early as 1992 an intergovernmental panel on climate change said "the combination of sea level and temperature rise, along with changes in precipitation and UV-B radiation, are expected to have strong impacts on marine ecosystems, including redistributions and changes in biotic production."

As the Earth warms, sea levels will also rise. There are two reasons for this. One is that water, when heated, expands, the other is that there will be more melting of glaciers and pack ice.

World sea levels and temperatures have fluctuated dramatically through geological history. At the last glacial maximum (18,000 years ago), the Earth was 5°C (9°F) colder and sea levels were some 100m (328ft) below today’s level. As the glaciers retreated, sea levels began to rise rapidly until about 6,000 years ago, when the rate of change slowed significantly. For the last century, global sea levels have risen at about 1 to 2mm per year. Scenarios of sea level rise under global warming vary widely. Estimates of sea level rise by the year 2100 range from 10cm (4ins) to 3.5m (11ft).

Coastal wetlands are likely to suffer the most visible impacts of the rising sea. When sea level rises slowly, the combination of inorganic and organic sedimentation can allow wetlands rise apace. But geological records suggest that little wetland formation is possible at rates of sea level rise exceeding 10mm (0.4ins) per year.

Loss of coastal habitat would have enormous ecological and economic consequences. Coastal wetlands act as sediment traps that stabilize coastlines, protect against hurricanes and storm surges and serve as nurseries for marine life.