You see them everywhere, from the Peak to Mui Wo. They are round every corner, along every roadside, hiding behind housing blocks and leaping at you from country walks. Apart from the common grey, the species comes in browns and greens, along with rather more startling reds and purples. Common, ugly and unloved, they can become a source of constant irritation if you let them. 'They' are the thousands of concrete slopes that seem to blight nearly every road and footpath around Hong Kong. Their unattractiveness brings out emotional reactions in onlookers. Angry Sai Kung resident Nigel Blandford wrote this year to the South China Morning Post, complaining that apparently stable hillsides in Sai Kung were being 'systematically stripped of mature, well-established vegetation' and replaced with 'stark, ugly' concrete. Jason Brockwell of Shek O wrote that 'innocent' slopes on the road to his home had received the treatment, making a once-pleasant journey 'like a nightmare trip through a low-budget alien landscape from an early episode of Star Trek '. Ask others and they refer to the scars on the Peak, Old Peak Road, Bowen Road, whole swathes of Kowloon - the list goes on. Mr Blandford appealed: 'Please let's keep the concrete gun, and its resulting ugly scars, as a weapon of last resort.' That, says head of the Government's Geotechnical Engineering Office (GEO) Dr Andrew Malone, is what government policy demands. A guideline was first issued 20 years ago, saying that shotcrete - concrete sprayed on the slope surface as a protective skin - should be used 'only if there is no other safe and practical alternative'. That the guideline was reissued in 1993 suggests it was being ignored. And Dr Malone himself says 'rules and regulations only work up to a point'. 'You have to inspire people to do it,' he adds. The crux of the problem, he says, is the ideal nature of shotcrete to make slopes safe. 'Shotcrete is such a wonderful engineers' solution,' he says. 'It's safe, quick - it's got everything going for it except that it looks awful.' People think tree roots entwined in the soil must be the best stabiliser. But research on how good they are at stabilising slopes has produced 'ambiguous' results, since trees also act as a lever on soil, says Dr Malone. Nature rarely produces slopes as steep as those that are cut by machines: the steeper they are, the worse trees are for holding them. And while the greenery grows, the slope is vulnerable to erosion. With the SAR's steep hillsides cut away to form flat areas for roads and housing, and about 60,000 or so artificial slopes on the Government's list for study, making them safe and keeping them that way, it is not surprising designers turn to the simple solution. About 10,000 slopes were registered before the GEO was formed in 1977, most of which were not up to current standards. Since 1985, the office has done the preliminary work on nearly all these and detailed work on about 2,000. Yet another 25,000 also existed but were unregistered and often unnoticed. These have been gradually revealed by a territory-wide aerial photo study that has contributed to a complete catalogue of artificial slopes just being completed. With the GEO able to deal with a few hundred slopes a year, it has brought in outside consultants to speed up the programme. Meanwhile, slopes produced since 1977 were supposed to be registered by developers, but this was patchy initially and a complete list of who is responsible for which slopes is being collated. For public slopes made since 1977, other government departments such as Highways (alongside roads) and Architectural Services (besides government buildings) are responsible for safety, but they do not have geotechnical expertise to design the slope protection. Instead they hire consultants or GEO to do the work, which is then approved by GEO. Then there are the slopes next to private premises, which are the responsibility of the owners. The GEO will check it for danger, but tenants' or owners' associations must get the work done. Surveys indicate that public perception of their responsibility is low. About 700 dangerous-hillside orders have been sent out since 1985, 200 in the past two years. Private owners opt for the quickest and cheapest method, with the bonus that concrete discourages mosquitoes and snakes. Given this situation, and Hong Kong's torrential summer rains that cause hundreds of landslides a year, GEO must win credit for the few deaths there have been in the past few years. Better building standards, fewer squatter camps - and luck - also play their part. The biggest disaster in recent years was the 1994 Kwun Lung Lau landslip when a retaining wall collapsed above a pathway, killing five people; three died the following year. Compare that with 138 people killed in 1972 and 18 in 1976 that spurred the formation of the GEO, and the hundreds who die in southern China. But GEO engineers agree the price cannot be the concreting of Hong Kong. 'Admittedly it may have been overused,' GEO engineer Alex Li Chi-on says. 'I don't like it.' A tour of Hong Kong Island and Kowloon slopes shows the problems - and the possibilities. On Barker Road, a slope stabilised with huge nails driven into it and the surface seeded in 1991 with a 'woodland' mix of shrubs and trees looks for all the world like a naturally overgrown hillside. There are more like this that people do not realise are artificial, Mr Li says. The Landscape Unit of the Highways Department has developed different mixes for application in summer and winter and to wet and dry sites. Yet next to it is a new concrete slab which, despite the retention of a few trees, scars the landscape. Mr Li says many of these are emergency repairs, with concrete applied to make a dangerous slope safe so that a road can be reopened or a housing block livable. The Barker Road site could only be landscaped because the steep slope could be cut flatter, Mr Li said. In other cases, that means cutting away trees at the top of the slope to plant trees, or cutting back prime land. But things are improving, he says. After Kwun Lung Lau, shotcreting was used liberally to make slopes safe, and many of these contracts are still ongoing. But of 360 slopes being treated, 150 will be planted while 133 will be concreted, and about 80 will get a mixture of both or a masonry wall. Managing director of slopes consultancy Mouchel Asia, Carmaine Siu Koon-hoi, claims about half the slopes his firm designs are green. 'We always try to restore vegetation whenever we can.' The perception that most slopes are concreted probably comes from roadsides, most of which are shotcreted because they are so steep, he says. That's where the strange colours come in. Highways Department technical secretary Chan Kee-man estimates that his department is in charge of about 10,000 slopes. Trials of pigments to make them blend in with the surroundings led to some rather startling pinks and bright greens at first, he agrees, but the browns now in use make the slope difficult to pick out from a distance. Mr Li shows off a slope being painted. It is a very odd purple. But, he insists, give it six months to weather and it will look like the one next door, which has a look more like rock than cement. Creepers planted at the base of other concreted slopes, plants in pots fixed into the surface or nicely decorated retaining walls are other ways of handling the problem. Mr Li has great hopes for a new Japanese system of fibre that can be applied even to steep surfaces to hold the soil while trees take root. In fact, Japan's research on different ways of revegetating slopes has been ahead of Hong Kong's for years. In the early 1980s another Japanese mesh system was tested and it worked on a Hong Kong slope but was expensive. A trial of the new method will be run next year to try to adapt it to Hong Kong's tropical conditions. Mr Li insists that cost is not a factor as seeding can be cheaper than shotcrete. But fundamentally, he admits, the problem is training and attitude. Engineers at GEO want to be sure that what they are doing will work, and are up against the vagaries of nature. He shows the Post one site where further work will be needed after seeding failed. 'Engineers consider vegetation an art rather than a science. Some vegetated slopes work, some don't. The engineer wants to do a calculation to show it's safe. For an engineer to do a green solution in that grey area he has to be brave and probably give the site a lot more attention to make sure it is built properly.' Government House is an interesting example. The effects of ongoing work to stabilise the slope at the bottom of the garden backing on to Lower Albert Road in Central will not be visible when finished, according to the GEO engineer in charge, Dr Ren Gang. No vegetation should need removing while the slope is fixed, he says. 'We fully realise the sensitivity of this site.' Yet just next door, outside the grounds, a slope between Upper and Lower Albert roads was shotcreted this summer, leaving a few trees but removing all the undergrowth. Friends of the Earth research co-ordinator Vincent Chen Rongjun says the GEO needs more ecological staff to counteract the engineering frame of mind. After research with American scientists at South China Agricultural University, he says the key to successful plant stabilisation is plant choice. Seeding is unreliable in Hong Kong because too many exotic species are used or too little attention is paid to the site. 'For different sites we need to select different species. There are many indigenous species but some that grow well in Kowloon may not grow in Hong Kong [Island].' The concrete should be seen as temporary while plants are small and erosion can still occur, but it should be demolished once they take over, he says. Concrete will crack if the underlying ground moves, whereas trees adjust with soil movement. Trees, shrubs and grasses will stabilise the lower, middle and top layers of soil. 'I visit many man-made slopes in Kowloon. I think more than 80 per cent are covered with concrete,' Mr Chen says. Chan Kee-man, the Highways technical secretary, points to turfing along the North Lantau Highway as an example of slopes made easier on the eye. The grass does not stabilise lower layers but discourages water seepage. Dr Malone agrees the Government must try harder in the face of increasing public awareness. Ironically, he says, the manual that standardised methods for slope design encouraged developers to cut steeper slopes, and that should be discouraged in favour of building more bridges and tunnels. But the public is far more worried about safety than aesthetics and he is aware views will change suddenly if another landslide proves deadly. 'It requires a willingness to innovate and we have to innovate very carefully because of a concern about safety,' he says.