Environmental conservation is a cause with which no one disagrees these days. The challenge lies in getting a consensus on what and how to conserve. When Secretary for Planning, Environment and Lands Gordon Siu Kwing-chue unveiled his plan for a pollution-free new town in North District in November, environmentalists applauded his undertaking to protect the wet agricultural land at Tsung Pak Long, also known as Long Valley, as an area of ecological and cultural value. But they have since learned they were wrong in assuming his undertaking meant barring the Kowloon-Canton Railway Corporation (KCRC) from building a new line through the area. Yes, the area will be protected, but only in the sense that the railway will not be built on the ground; it will be carried on a viaduct instead. The KCRC says it has to stick to the planned route, because options to the north and south will cut through businesses and houses. The company considers that the planned route strikes a right balance between the environment and the impact to the area's residents. Environmentalists are not convinced, however, that enough has been done to preserve one of Hong Kong's few remaining sanctuaries for birds, including some rare species. They want the KCRC to choose another route so the area can be left as it is, even though it would entail paying millions to compensate displaced residents. Local villagers, meanwhile, are dismayed that environmentalists are asking them to give way to the railway - and the birds. The passionate views held by the three sides involved in this controversy reflect deep differences in values. Crudely stated, each puts a different price tag on the environment. For environmentalists, the ecological cost of building a railway through Long Valley is incalculable because it would irreparably damage the area. For the KCRC, a government-owned entity run as a commercial enterprise, there has to be a cap on how much it can afford to pay to protect the environment. For the villagers, keeping their homes undisturbed and reaping the benefits of development are more important than keeping the valley as a habitat for birds. Under any circumstances, balancing their interests and priorities would be hard. But it would help if all are prepared to put a bigger price tag on a piece of land that has hitherto survived excessive human exploitation, so that nature can be allowed to take its course there. And if an agreement could be reached on a 'price' which would make all sides happy, the Government should be prepared to chip in to bridge the differences.