At present, tree inspectors need to pass an exam with 200 multiple-choice questions. This test needs only sketchy knowledge and can be passed with some luck. A certified inspector with one year's experience may not know how to tackle problems arising from hot and humid weather, for example. Current exams are not suited to local conditions.

This has caused many people to ask for an up-to-date and locally oriented registration system.

A new system could broaden the knowledge of tree workers and landscape managers. Several government departments have people working with the city's trees, but many of them lack experience in a city environment. This might be one of the reasons our trees are so dangerous.

It is easy to see they don't really know what they are doing because they even choose the wrong kinds of trees to be planted. There have been reports that tree workers have made bad mistakes. For example, they chose the Taiwanese acacia, a large species, to be planted at concreted roadsides. These trees cannot send down deep roots and so it is quite likely they will fall over. Every day newspapers also report that officials make mistakes about whether or not a tree should be cut down.

The government should realise how urgent it is to have a system in place to improve the situation.

Chan Yik-tsz, CCC Heep Woh College

Listen to the band, that's what I say

A musical ensemble is a group of musicians. Different groups have different styles and sounds.

In classical music, trios or quartets either blend the sounds of several instrument types - e.g. piano, strings and wind - or group together instruments from the same family, such as string or wind.

In jazz groups, instruments typically include brass (saxophones, trumpets etc.), one or two choral 'comping' instruments (electric guitar, piano or organ), a bass (electric bass guitar or double bass), and a drummer or percussionist.

In rock bands, there are usually guitars and keyboards (piano, electric piano, Hammond organ or synthesisers), and a rhythm section made up of a bass guitar and drums.

I like band music. Some people say it's too noisy, but I find it exciting.

Chu Chun-yin

Light pollution in Hong Kong

Hong Kong is famous for its scenic night views. Buildings decorated with flashing and changing lights and neon signs make the city one of the brightest spots on earth. But such decorative lighting is really just light pollution.

Many people who live in busy districts such as Wan Chai, Causeway Bay and Mong Kok complain about the flashing lights. Bright advertising signs keep them awake at night. The lights make them dizzy and stressed.

Light pollution also contributes to global warming. The electric lights consume lots of power. Electricity is made by burning fossil fuels, which increases the level of carbon dioxide in the atmosphere.

Some night-time birds use the moon and the stars to find their way from point to point during their migrations. But they lose their way when flying through brightly lit areas. It's estimated that each year at least four million birds die because of light pollution. The feeding and mating habits of some reptiles and mammals are also affected by bright lights shining at night.

The government should pass a law limiting the use of advertising lights. For example, no neon signs need to be on past 11pm. Similarly, buildings should not be allowed to display overly bright or flashing neon signs opposite people's homes. Secondly, advertising signs should have time controls allowing them to be switched off or dimmed. This would save a lot of energy.

While some people think all this extra lighting is part of Hong Kong, we really need to consider the rest of the world and the impact we have on it with our actions.

Shara Shek, St Antonius Girls' College