Are tourists enticed by these unique attractions threatening their very existence?

The two young sea-lions took not the slightest interest in our arrival. They were playing on the jetty, rolling over and tumbling into the water together, entirely ignoring the human beings edging awkwardly round them.

The two young sea-lions took not the slightest interest in our arrival. They were playing on the jetty, rolling over and tumbling into the water together, entirely ignoring the human beings edging awkwardly round them. Our party then had to step gingerly over hundreds of marine iguanas basking on the rocks, strange creatures with richly coloured velvet coats, looking like something between a giant lizard and a miniature dinosaur, and found nowhere else on earth except here in the Galapagos.

A little further on were the blue-footed boobies, birds with brilliant china-blue feet, again unique. And then there were the flightless cormorants, birds with vestigial wings who, over the generations, have lost the ability to fly because the nutrients at the shoreline are so rich they have no need to leave.

The island of Fernandina lies at the far western edge of the Galapagos archipelago, dominated by a volcano that last erupted only six years ago, and home to some of the most remarkable wildlife in the world. It was late afternoon on one of the last days of the year, and we had come ashore to scramble round the rough dark lava rocks of Punta Espinosa on the island. In the golden afternoon light, with the moon rising above the volcanoes on Isabela Island across the strait, we could be forgiven for thinking that we were guests in paradise.

The creatures you see in the Galapagos are remarkable in their rarity. They are even more so for their lack of fear. They don't run away. They carry on basking or playing or mating or incubating their eggs or fighting for territory with blissful disregard for human beings. It is as if you are walking into a David Attenborough programme, and finding that the real thing is even better than you ever imagined. The closeness of the living natural world, in this environment of volcanic rock and sweeping beaches and sparse vegetation, makes the Galapagos experience special.

The colours help, too. The intense black of the rock, the startling blue of sea and sky, the crimson of the mating frigate-birds, the yellow of the warblers, the brilliant orange of the American oyster-catchers, the glistening silver of hundreds of dolphins swooping round your ship in the dawn light.

We spent eight days in all, aboard a boat called Tropic Sun, visiting all parts of the islands. We lived, ate and slept on the boat and went ashore two or three times a day, to walk the trails, see the wildlife, and snorkel in the sea. The boat was hardly the most luxurious experience we'd ever had, and was certainly not a centre of gastronomic excellence. But that really wasn't the point. It took us to the places we wanted to see; and the expert guide we had, who led us round the trails and explained the flora and fauna to us, was the best we could possibly have wanted.

You need not be an inveterate birdwatcher or naturalist to be captivated by what you see. You simply cannot help being taken over by a sense of wonder at this different and special world.

Darwin's visit, in 1835, aboard HMS Beagle lasted five times longer. He marvelled at the tortoises and the iguanas, but it was the tiny finches that jolted his imagination most vividly. They are still called Darwin's Finches in his honour. There are 13 different species of the finches across the islands (our group managed to see five or six). The fascination is in the beaks. Each species on each island has, over time, developed a differently shaped beak, adapted to the vegetation and the competition in that particular location. These tiny birds with tiny distinctions helped to produce one of the greatest ever advances in the history of scientific thought.

Since Darwin called, these islands on the Equator have struggled to maintain the fragile balance of their ecology. Over the years, the indigenous animal population has been under increasing threat, from wayward fishermen, or from feral dogs, goats and rats escaping from human settlements or boats.

Recently the Ecuador authorities started trying to eradicate the invading species, and have now succeeded in freeing some entire islands from non-native creatures. A giant tortoise breeding programme is in place, rearing infants in a protected environment at a time when they are at greatest risk, and then returning them to the wild. And there are strict laws now in place against harming or destroying the wildlife – though only recently a group of 12 slain tortoises was discovered killed apparently for the Japanese aphrodisiac market.

The most serious ecological threat, however, is posed by the greatest economic boon the islands have ever had: tourism. Ninety boats, ranging in size from 12 passengers to 100, do the rounds of the islands. And on the whole, the schedules are managed well. The itineraries are staggered, so that at most two or three boats might appear at one location at the same time. When you go ashore you have to be with a guide, you cannot stray from the marked trails, and you cannot touch the wildlife. One of the passengers on our boat was roundly and rightly chastised for stroking a young sea-lion – an action with potentially fatal consequences for the sea-lion because of the risk of rejection by the mother.

In a country as poor as Ecuador, the temptation to increase the numbers of tourists is always there. We were told there's been a recent request for permission for a much larger boat to travel round the Galapagos, carrying some 500 passengers. I shudder to think what might happen if such a boat arrived at Punta Espinosa and disgorged everyone on to Fernandina Island at the same time. Not only would the shock of a thousand tramping feet endanger the rock, the sand, and the teeming wildlife that depends on it; but it would seriously degrade the quality of the visitors' own experience.

Herein lies one of the oldest dilemmas about the evolution of tourism. We value, and to want to visit, the unique and fragile environments of the world. Yet in visiting we risk destroying the very qualities that render those places so enticing. This is especially true where the rarity of the place is quite so marked as it is in the Galapagos.

Responsible tourism lies in absolute respect for the location and its inhabitants. It lies in treading carefully wherever we go. It lies in ensuring that the economic contribution we make by going helps to conserve rather than to destroy. And it lies in developing the international networks protecting endangered species and world heritage so that they can make a difference on the ground.

Fortunately, in the Galapagos, Charles Darwin would recognise much of what he saw if he returned today. It is our duty to ensure that he would recognise it again, another two centuries hence.

The Right Honourable Chris Smith, MP, was formerly Culture Secretary, and responsible for tourism in the UK.

He and his partner paid £2,000 each for a package through Green World Adventures in Quito ( This comprised Iberia flights from Heathrow via Madrid to Quito, onward flights to the Galapagos Islands, and eight days' full-board on the Tropic Sun