The size of country parks in Hong Kong is irrelevant to the housing discussion. When there is abundant land in the plains, there is no reason at all for going to the hills.

Maybe people targeting country parks have in mind houses with a view for the rich. But even that does not work south of Chi Ma Wan. Just look at the failed "luxurious" Sea Ranch project at Yi Long Wan.

I share the frustration expressed by Jo Wilson ("Clean-ups at beaches make a difference", May 11) and other correspondents about the growing amount of trash in the ocean and on Hong Kong's abundant coastlines.

We agree that cleaning up is a band-aid approach, and we must tackle the issue at the source.

The current situation in Hong Kong is dire, and getting worse. Our beaches, streets, and country parks in this "world city" are dirtier than those in many developing countries. Eight million tonnes of plastic enters the ocean each year, and China, including Hong Kong, has just been named as the No 1 culprit, according to a recent global survey.

But thankfully, as proven by the Hong Kong Cleanup Challenge, citizens are ready to act. We are thrilled to be having our 15th anniversary this year, and the theme is "The Spirit of Collaboration". We are organising Hong Kong's first ever zero-waste week, from June 7-14.

Zero waste is a goal that is ethical, economical, efficient and visionary, to guide people in changing their lifestyles and practices to emulate sustainable natural cycles, where all discarded materials are designed to become resources for others to use, and re-establish the balance of nature.

We are challenging all individuals, schools, offices and businesses to send less to landfills. Whether you simply pledge to use zero disposable plastic bags, bottles, straws, cutlery or takeaway containers, every bit helps. The world's leading zero-waste experts will take part in a series of events, including the Global Zero Waste Summit on June 11 at Cyberport.

The Hong Kong Cleanup has become a civic movement, led by the local people of our city. We will continue to innovate, and come up with creative solutions to clean up Hong Kong.

I refer to Alex Lo's column ("Confusion reigns over Israel's 'capital'", May 6).

The Jewish state of Israel is a very small country and Jerusalem is its capital. Israel declared it as its capital just as any and every other country in the world has the right to do.

The trouble the world finds with that is, like Christian Europe before, today Arab Muslims claim the significance the city of Jerusalem represents for them.

Christianity and Islam have their roots in Judaism, Christians acknowledge this, Muslims do not.

Lo ought not to be confused about Israel's capital.

Before the six-day war, in 1967, when East Jerusalem was under Jordanian rule, there was no outcry nor international effort to declare it a capital of the Palestinian state.

In fact, Jordan ruled all of the territory known today as the West Bank, while Egypt ruled Gaza. From the end of the British Mandate in 1948 until 1967, Arab countries never attempted to create a Palestinian state, nor did the international community.

Jerusalem is an ancient Jewish city first established by King David in 1,000BC and it is Israel's capital.

I congratulate China and Pakistan on agreeing to US$45 billion worth of infrastructure and energy projects. However, I am concerned about the safety of engineers and other workers who will be employed on some of these projects.

I am worried that they could be targeted by organisations such as the Taliban. Some groups will probably try to kidnap some of these workers and then ask for huge ransoms.

Both countries should coordinate their military actions and ensure these people are given adequate protection at those locations where they may be at risk.

I refer to the letter by Jasmine Poon ("Firms do not always behave in ethical way", May 12).

Of course in Hong Kong, there are high-profile and financially successful companies, such as Cheung Kong, which accept corporate social responsibility and adhere to business ethics.

However, there are also firms in the city which, by contrast, have a very bad reputation with officials in the Labour Department. The bosses of these dodgy firms are known for their broken promises to employees leading to low morale and high staff turnover.

Unfortunately, there are still too many of these kinds of lousy companies in the city. Their chief executives would not know the meaning of business ethics and exploit their hard-working employees.

These are the kind of employers who try to avoid making Mandatory Provident Fund payments and fail to provide adequate insurance or annual leave for employees.

Workers at these rogue firms face substandard medical policies and sometimes have to take pay cuts.

I refer to Jake van der Kamp's column ("MTR repeat offender on disclosure law", May 12).

The MTR Corporation always keeps under careful consideration its disclosure obligations under the Securities and Futures Ordinance and the listing rules of the Hong Kong stock exchange.

We note the views expressed by van der Kamp, including assertions that are unfounded.

Regarding certain statements about the estimated construction costs and timing of completion of the express rail link project, van der Kamp says that "the corporation has made no public announcement. This clearly breaches the legal requirement that the public be told in a timely manner"

Van der Kamp may be unaware of the public disclosures we have made regarding the contractual responsibility for the project cost for the express rail link in a series of announcements and press releases issued in 2014 and 2015 and in our most recent interim financial report and annual report.

The MTR Corp believes that it has announced "inside information" where appropriate and will continue to do so in the future.

I refer to the letter by Conrad Wong Tin-cheung, chairman, Hong Kong Green Building Council Limited ("Having green features in buildings should not be mandatory", May 13).

There are increasing demands for energy globally which can cause serious environmental problems. Shopping malls, homes, schools and offices all need air conditioning. And while these demands must be met, most of us still do not pay enough attention to the environment.

I certainly think it would help the environment if more of our buildings incorporated green features.

For example, they could get renewable energy sources from nature, such as solar, wind and water power.

Solar energy, for example, creates no pollution and can also be used for heat insulation.

Wind power is not widespread in Hong Kong, but you do see examples of it on Lantau. Again, it does not cause any pollution or add to the greenhouse effect.

The government has a role to play. For example, it could help with the planting of trees so buildings in areas like the central business district could have rooftop gardens.

Individuals can also do simple things which can make a difference, such as using fans wherever possible, instead of air conditioners.