It is a laudable objective and a hopeful trend. With between 10 and 30 per cent of all non-business travel by North Americans and Europeans now broadly classified as eco-tourist, the profits are enormous, and so are the potential benefits to both nature and neighbouring peoples.

But its very profitability attracts principals who appropriate the label while dispensing with the substance. In the absence of accepted standards, the integrity of the concept may over time erode, triggering disenchantment and depriving wildland communities of the income they desperately need to avoid being driven to destroy nature for their own survival.

Eco-tourism emerged from such desperation. In the early 1970s, poaching of elephants and rhinosin East African national parks, largely by poverty-ridden local hunters, left herds decimated. Conservationists seeking to stem the slaughter concluded that only by giving neighbouring communities an economic stake in their preservation would they relinquish their hunting tradition. Around the same time, tropical biologists and ecological activists concerned with the wholesale harvest of fragile South American rain forests proposed environmentally conscious tourism as an alternative to the logging and mining that had long been the mainstays of the region's economy.

Meanwhile, many developing countries began to question the social costs of conventional mass tourism. Drugs, AIDS, prostitution, currency speculation, and offensive cultural imports all undermined local values and traditions while 50 to 90 per cent of the profits flowed back to the developed world from which the tourists came.

Developing country governments saw in eco-tourism the possibility of a less destructive and potentially more profitablealternative. A South African study found wildlife tourism 11 times more profitable than cattle ranching, while a Kenyan study estimated that a single elephant herd garnered $ 610,000 a year.

With such bright prospects, over the past two decades eco-tourism has swept the earth's remaining wild places in both the developing and developed worlds. In some countries it has become the largest foreign currency earner, exceeding bananas in Costa Rica, coffee in Kenya, and textiles and jewellery in India.

In 1997 Latin American nations alone invested $21 billion in eco-tourism. Major environmental organisations, international aid agencies, universities, and tour operators have all adopted programmes featuring educational travel to wild places.

But much of what calls itself eco-tourism is in fact ``greenwashing,'' or ``eco-tourism lite,'' notes Martha Honey, author of the newly-published book, Eco-tourism and Sustainable Development: Who Owns Paradise? (Island Press, 1999). A tour outfit can purchase a GreenGlobe logo purporting to represent its commitment to environmental improvement for as little as $ 200 without having to meet any standards for compliance.

By their scale and style alone, some ostensibly ``green'' tourist developments betray their own professed principles. In Costa Rica, for example, a $3.0-billion ``ecodevelopment'' called `Papagayo' is slated to include shopping centres, two golf courses and polo field. On Mozambique's southern coast, a US developer is building an $800-million ``beast-and-beach eco-tourism paradise'' featuring a floating casino, hippos in the golf course ponds, imported wildlife, and Bushmen from the Kalahari desert -- all at the expense of the 10,000 local farmers and fishermen who will be displaced by the development.

Who can afford to visit these luxury resorts? In such a large and varied industry, the entrance fees vary widely but they are never cheap. Some exclusive enclaves run as much as $600 per person per night. others employ a kind of reverse psychology thatappeals to the inner masochist, charging for each additional discomfort or inconvenience.

In East Africa the rapid development of private wildlife preserves has coincided with and to some extent accelerated the deterioration of national parks. Many of these preserves belong to white settlers who, in the aftermath of decolonisation, have reconstituted their estates as private conservation parks in order to retain a colonial lifestyle and their family wealth. Often better financed and managed than the government-run parks, they siphon off the tourist traffic that is vital to the parks' viability without providing much employment to locals or contributing appreciable taxes to the upkeep of neighbouring public lands.

Despite its many pitfalls, however, eco-tourism still holds promise of being substantially kinder to the earth than conventional tourism. But the many eco-tourist experiments that remain committed to its first principles are mostly small operations with meagre resources to market their servicesand no capacity to compete with the big boys. To survive, they will need to establish and enforce rigorous shared standards and to market their uniqueness to a broader public in ways that they can't individually afford.

One remarkably successful model for such a movement is the American organic food and farming industry. Now a $ 3.0 billion market expanding by 25 per cent a year, organic foods have retained the confidence of consumers by virtue of a rigorous third-party certification process set in place by early organic farmers a decade ago that ensures the integrity of the organic label.

Organic food consumers are so fiercely persuaded of the validity of these standards that when a federal agency recently sought to dilute them by allowing bio-engineered foods to be labelled organic, a record 200,000 letters flooded the Department of Agriculture and forced a policy reversal. If eco-tourism is to preserve its integrity, it must adopt such a certification system -- and soon, while the faith and commitmentof conscientious travellers remains intact.