Today, global environmental pollution grows serious, severely threatening the existence of humankind.

To take a typical example, about 14 percent of coral reefs of the world disappeared over the past 10-odd years owing to the rise in sea water temperature and the pollution of ecological environment caused by global warming.

If it continues at the present rate, all reefs will totally disappear from the earth in the present century.

A few years ago, whales, dolphins and turtles died in groups in the western and southern waters off Sri Lanka.

It was because a cargo ship loaded with large quantities of chemicals sank to pollute the waters.

Plastic waste called a “white pollutant” already became a major factor threatening ecological environment.

Plastic waste is rampant in all areas of human life.

Plastic bottles are most eye-catching in the seas worldwide.

A truckload of plastic waste is dumped into the sea every minute and thus a large number of plastic pieces are floating on the sea. If they are all linked, it might coil around the earth hundreds of times.

Some countries carelessly burn plastic waste to cause serious air pollution, resulting in hundreds of thousands of human deaths from respiratory diseases every year.

The burning of plastic waste entails huge amounts of greenhouse gas.

The situation compels many countries to make a big effort to protect ecological environment.

They strive to develop a new generation of materials which can substitute plastic while reducing the production and use of plastic goods.

Many countries and regions prohibit the use of disposable plastic products which are indestructible.

Some countries took a measure to ensure that biodegradable bags are used instead of plastic bags.

On the other hand, efforts are made to process plastic waste into fuel and building and other materials.

In Cambodia, tourists from home and abroad throw away about 116 200 tons of plastic waste every year. So it is implementing a plan aimed at decreasing the amount of plastic waste from the sector of tourism by 75 percent till 2030.

Information work is intensified to protect environment and rational measures are taken for the disposal of plastic waste.

The greening of architecture is pushed ahead with as part of the work to protect ecological environment.

Green architecture based on the principles of ecology helps minimize the consumption of resources and energy and provides people with good environment.

The construction of roof gardens and roof greens is promoted as they can not only improve the effectiveness of heat insulation in densely populated cities but also increase oxygen content in the atmosphere, absorb carbon dioxide from it and filter dust out of it.

Especially, roof greening is notable.

Roof greening is classified into flat and cubic types according to greening space, ecological and relaxation types according to purpose and peripheral, fixed and mobile styles according to form.

Many countries set roof greening as an important task to improve environment and are accelerating its implementation.

Experts predict that international efforts will become more positive to protect ecological environment.