They belong to the planet's most endangered species, but I'll bet Tian Tian and Yang Guang felt more threatened than ever before in their lives when they landed in Edinburgh yesterday.

Rather than being quietly eased into their new quarters after their flight from China, these shy animals were greeted by skirling bagpipes, flashing cameras and the well-meaning cheers of excited crowds. The world's rarest bears could have been forgiven for expecting to see the Reliance logo on their van. Idolised as they are, these pin-up pandas are as imprisoned as any jailbird.

The arrival of the iconic creatures has been claimed as a diplomatic coup for Scotland, and a much-needed boost for Edinburgh Zoo. The photogenic couple are certainly the most exotic beasts Scotland has seen since a sighting of Angelina Jolie and Brad Pitt in Glasgow earlier in the year. Yet lest anyone be under any illusion, these giant pandas are not being treated as animals, not in the true sense of the word. Like royal brides in the Middle Ages they are political pawns, and will be handled accordingly: with great fanfare and ostentatious care, but with no chance of ever being allowed to be pandas as their cousins in Sichuan or Shaanxi would understand the word.

Yesterday, LibDem MSP Willie Rennie expressed the hope that the 10-year loan of these bears will allow Scotland to raise the issue of Chinese human rights abuses. Fair enough. But what about animal rights? These pandas have been catapulted into the ursine equivalent of Big Brother, with no hope of ever being voted out. Unlike Big Brother contestants they do not love the limelight. Quite the opposite. In their home environment, giant pandas live alone, or with their cubs, and mix with the opposite sex only once a year, solely in order to mate.

Now, I'm not accusing Edinburgh Zoo of cruelty. The pandas' keeper is a bear expert, there will be specialist vets on call, and their compound is so well-designed one can almost picture Kevin McCloud emerging from behind a bush to rhapsodise over its charms. But for all its climbing trees, foliage and bathing pools, it is still a cage. The pandas will not be in anything remotely similar to the forests of south-west China where they belong. Instead of the scent of trees, they will smell petrol from the Corstorphine traffic and burgers and chips from the gawping crowds. Eyes will be on them almost every hour. And if, as hoped, Tian Tian gives birth, attention will grow even more intense.

That longed-for cub, by the way, will also be a captive for the rest of its days. That's one of the drawbacks to breeding pandas in zoos: offspring are condemned to a life behind bars. The human equivalent would be taking two youngsters from Possil and putting them into Eton for a decade, then expecting them to be able to fend for themselves back home. The odds on survival would be slim.

Around 1600 pandas live in the wild, and another 300-odd in captivity. Survival of the species may depend on breeding and researching caged bears, so it makes sense – for everyone, that is, except the captive bears. Something like £8 million will be spent on the Edinburgh panda exchange in the next decade. If this were not primarily a business investment for zoo and nation, such a sum could surely be more imaginatively and humanely used to help preserve the pandas' natural environment and protect them in their own terrain. After all, if they cannot be maintained in the wild, do we really want a captive panda population we can only stare at through the bars and never set free again?

No matter how well they are cared for, or how popular they are, or how big a political statement they make, pandas in confinement are not the animals they should and could be. I would rather these bears became extinct than that they lived like this. Of course, apologists for zoos will point out that pandas live twice as long in captivity as in the wild. I'm not much good at arithmetic, but by my calculation that's still only half a life.