First person

PUBLISHED : Thursday, 05 February, 2004, 12:00am
UPDATED : Thursday, 05 February, 2004, 12:00am

Cheung Kwok-wai, 44, is a senior country parks officer with the Agriculture, Fisheries and Conservation Department. Mr Cheung turned his love of plants into a career and has been a botanist with the department for 12 years. The officer, who spent his early days documenting the history of Hong Kong's plant life, has a mission to save the city's flora from a killer weed.

'I have loved hiking in the countryside since I was young. I love to see Mother Nature in all her glory and this is probably the reason I chose to major in botany at the University of Hong Kong. It may seem boring, if not odd, to study weeds and trees, but it isn't entirely true. There are a lot more than just weeds and trees in my areas of interest.

What interests me the most is plant ecology. To be able to understand the various interactions between plants and all other living organisms in their environment can be fascinating. It is one of the most important areas of modern science and can help us to better understand how humans are changing the face of the world.

These interactions help explain many unknowns in nature, such as why some plants grow faster than others, how some plants resurface after being unseen for years, or why it takes so long for some plants to blossom.

Working with the department for more than 12 years, I have seen greenery in Hong Kong diminishing. While this is unavoidable amid rapid urban development, at least 40 per cent of the vegetation in Hong Kong is protected by the country parks. I am very pleased that as a country parks officer I have managed to protect some of the plants.

My three years with the department's herbarium was the most rewarding experience in my career. Although the plant library is relatively young, with only a 112-year history, this is where I learned the most about Hong Kong's vegetation. Going out with plant collectors in search of strange plants that I couldn't identify myself was great fun. This was also when I first encounter Mikania micrantha, commonly known as mile-a-minute weed.

This invasive weed blankets the ground and trees alike, blocking out sunlight. When the trees and shrubs are dead, food for other woodland inhabitants is reduced. Due to having windborne seed, the killer weed spreads quickly.

Mikania started its rampage through the New Territories in the 1970s and 1980s, putting our country parks in jeopardy. Manual eradication is the most effective measure in Hong Kong. But if the roots are not removed, it will regenerate in warm, moist weather, particularly around November. This is probably why many people describe the noxious climber, introduced from South America, as green cancer. This is a bit of an exaggeration. In its native countries there are insects which eat it, but in Hong Kong it is left alone.

A herbicide, sulfometuron-methyl, has been introduced after a collaborative two-year research project with the forestry administration of Guangdong province. Trials in Pat Sin Range Country Park, Tai Po, proved satisfactory with a 95 per cent kill rate after the first application in April 2002. The herbicide not only killed the weed but opened up ground space and prompted the growth of local plants.

This spraying method is more cost-effective compared with manually removing the weed, but there still needs to be more research on the herbicide before it can be used on a wide scale. It is still too early to say if we have found this is the best way to eradicate the weed, but I am optimistic that we will find the answer.

While it may be unrealistic to think we can make Hong Kong free of Mikania, at least I hope it can be eradicated from some prominent areas so trees can grow healthily and the public can enjoy more woodlands and trees. This will improve the ecosystem and enhance the biological diversity in our environment. This is my wish.'