The greenhouse effect is a natural feature of the earth's atmosphere.

Certain gases, such as water vapour, carbon dioxide, and methane, are called 'greenhouse gases' because they trap solar heat in the lower atmosphere.

Without them, our planet would be frozen and nothing would be able to live on it.

But humans add to these gases, producing pollutants that cause a build-up of the greenhouse gases in the atmosphere.

Most important of the gases produced as a result of human activity is carbon dioxide, which is given off whenever carbon-containing material - such as coal, oil, or wood - are burnt.

As the planet warms up, the ice caps at the North and South Poles melt. When heat from the sun reaches these polar regions, the ice reflects it straight back into space.

If we melt some of the ice-caps, less heat will be reflected. This is likely to make the earth get hotter. More water will also evaporate from the oceans into the air.

Water vapour is a greenhouse gas. So again, extra warming is likely to occur.

As the atmosphere's energy balance changes, there could be dramatic changes in the weather in some parts of the world, causing massive fluctuations in temperature and rainfall, and greatly altering crop-growing seasons.

Mangroves and coral reefs appear to be in the front-line with regard to the impact of global warming on nature.

Sea-level position is central to the functional ecology of a mangrove swamp and a coral reef.

A rise in sea level will disturb every aspect of these two ecosystems, and combined with climate changes and stresses from human disturbances, the world's mangroves and coral reefs are likely to face severe disruption in the next few decades. WWF HK is a local charity environmental organisation established in 1981. Our mission is to build a future in which people can live in harmony with nature. For further information, please call 2526 1011.