Back in 1984 a 'new low price' for a Round-the- World airfare of £1,250 was announced by British Airways/Air New Zealand. Suddenly, jet travel had not only made foreign holidays affordable for mass tourism in the Mediterranean, but also opened up distant horizons for everyday travellers. Now, in the early twenty-first century, the price of a similar ticket has fallen to as low as £700, and a generation of students have grown up with the concept of taking a year out before university to see the world on just such a ticket.

As a result of such affordability of travel, both for leisure and business travel, the World Tourism Organisation forecasts a continuing explosive growth in international travel. Already there are 800 million international visits a year, and WTO predicts this will double again in the next two decades.

Such rapid growth has seen the travel industry grow from its initial 'luxury goods' status to become the biggest industry in the world, ahead even of oil. So with such massive economic considerations at stake, the industry is rapidly expanding its interests globally: airlines are forming global alliances and mergers, and large tour-operating concerns like Thomas Cook, Thomson and Airtours are becoming parts of multi- national conglomerates.

Naturally, such huge growth also precipitates huge infrastructure change. And whilst ever-larger aircraft may somewhat ease congestion at airports, and modern technology may continue to make aircraft quieter, the environmental lobby is inevitably stepping up its efforts to minimise the impact of tourism on historic monuments, on coastlines and on the biodiversity and cultural heritage of host countries - as well as the ozone layer.

When I worked for the large UK tour-operating group Thomson Travel in the late 1980s, a group of MBA students from France did a survey amongst the directors. Apparently I was the only one who was sceptical about their thesis that tourism could be made more 'environmentally friendly'. After all, at its core, the concept of chopping down forests for all the travel brochures (Thomson alone was printing over 30 million brochures a year in those days), and of fleets of aircraft flying millions of charter passengers to the Mediterranean and beyond, was hardly a propitious starting point; let alone the questionable aesthetics of many of the burgeoning tourist developments around the world's coastlines and beauty spots.

But during the 1990s my perspective on this was changed by a number of events and observations.

When I had first joined the travel industry in 1979, Spain was still a relatively poor, developing nation, just emerging from Franco's dictatorship. But by the 1990s it had joined the EU and was as thriving a first- world democracy as any of its northern European partners, with huge social and infrastructure advances for the whole population afforded out of the massive inflows of tourism income to its economy.

The concept of this 'levelling' of the economic playing field for poorer nations which can benefit from tourism (the Caribbean and Indian Ocean islands, such as Mauritius, are other good examples) is a powerful justification for the occasional tourist blackspot, given the economic and social empowerment that this redistribution of wealth can create for the local population over time. And, after all, who is to say that the high-rise red dots on the map representing Palma Nova/Magalluf, Pattaya or Ochio Rios have 'spoilt' Majorca, Thailand or Jamaica in their totality, any more than Blackpool or Bournemouth have 'ruined' Great Britain overall? The balance of the environmental and aesthetic downsides of such tourist playgrounds, versus the broader benefits that can result for local economies, is more evenly weighted as an argument than many a purist conservationist, who objects to tourism development simply on principle, might have us believe.

But even directly in terms of conservation, this flow of tourist income into poorer local communities can also transform their very ability to care for their local environment - an environment which might otherwise be threatened by the lack of basic economic welfare for the local human population, let alone for such relative 'luxuries' as heritage sites or wildlife preservation.

I was struck, for instance, by the transformation of local attitudes towards reef protection in Palawan in the Philippines, when I visited the remote area of El Nido for my honeymoon. Almost overnight, the locals had changed their main occupation from dynamite-fishing (which had disastrous consequences for one of the best reef areas of the world) into dive-guiding for tourists. They were thus transformed from destroyers of the reef into its very guardians, which is good news on a global scale.

This same poacher-turned-gamekeeper transformation due to tourism has also been seen to work in some parts of Africa, where locals have been educated to understand that protecting the wildlife and game - rather than hunting it into extinction - is good for promoting tourism, which in turn creates employment for their communities.

Now that the World Tourism Council has established that one in eight people globally is directly or indirectly employed by the tourism industry, such economic arguments are powerful motivators indeed - and they provide an inducement for local and national governments of tourism host-nations to become directly involved in preserving and protecting what might otherwise become lost to the world.

Another graphic example of this which I have seen in action is at the Cango caves in South Africa, the third largest cave complex in the world. These are now specifically being preserved as a tourist attraction, whereas previously - just like the caves in England's Cheddar Gorge - they were being completely despoiled by the very geologists who were exploring them.

So, far from being seen as inevitably a pariah in terms of conservation, there is in fact a strong argument to suggest that the tourism industry, as the world's largest employer, can and should harness its huge financial muscle directly in favour of conservation and the host economies, to promote local welfare and environmental good. And this argument becomes even more powerful when coupled with the fact that this must anyway be good for the travel industry itself: it will ensure a better balance for the future between the ongoing growth of the industry and the capacity of host nations and local environments to cope, and thus help to preserve the future of the travel industry too.

Evidence that such a harmonisation of interests and balancing-out of apparent opposites is already happening can be seen in a number of movements and initiatives now established or gathering momentum. The Tourism For Tomorrow awards (initiated by the UK's Federation of Tour Operators and sponsored annually by British Airways) now receives widespread international interest, both in terms of submission of entries and of media coverage for the winning tourism projects, which work in harmony with, or directly to protect, the local environment.

Governments and international politics are also playing their part. A recent United Nations initiative (UNEP) is attracting support from European tour operators to co-ordinate new sustainable tourism standards; and the British government's Department for International Development has announced funding for tourism projects which support sustainable environment programmes in poorer countries. The latter follows research which demonstrated that positive links could indeed be encouraged between tourism and poverty- reduction, and also environmental sustainability.

So the interests of conservation and tourism are becoming more in tune with one another as the travel industry matures, and the realisation dawns for shareholders of travel companies that the key 'asset' in their balance sheet which they must protect is the very environment in which they trade, and which their customers wish to enjoy. And in tandem with this, conservationists and scientists have awoken to the huge economic power of the tourism industry which can either work for the good or else cause despoliation and damage if not properly planned and environmentally audited.

Of course, the wheel may eventually turn full circle anyway, as the capacity of the planet eventually fails to be able to absorb further tourism growth, or if governments succeed in their intention to levy 'green taxes' on the travel industry (as they have for instance on petrol) in order to curb this very growth.

Or perhaps the explosive growth of international travel will be seen as only a twentieth-century phenomenon, curtailed in this new century by environmental constraints and by the fact that modern video-conferencing techniques may make business travel less necessary anyway. Furthermore, with the future possibility of our being surrounded by 3-D holograms of a place, with all the sights, smells and sounds recreated artificially, we may want to visit facsimiles of foreign places much nearer to home. Already, Americans can view the false Venetian canals and bridges of the Venetian Palace Hotel in Las Vegas. We may simply book virtual trips to far-flung places, without having to leave home at all.

Now that really would be good for the planet.