I'm going to hold my hands up right now. I don't ride a bike to work because it's good for the environment, nor do I ponder how to wear a skirt while upon two wheels. My bike of choice is not a Pashley or a Charge Plug, it's an Evil Revolt – at least in my dreams.

I love bikes and I love riding them hard and fast down mountains. Ethical living? Head to Aston Hill on a Saturday and you'll see more rock'n'roll than eco-friendly.

Yes, I'm afraid it's true. I'm a mountain biker, cycling that thin line between loving the environment yet engaging in a sport that, when practised badly, actively destroys the landscape. It's a dilemma also pondered by skiers – is it possible to preserve the mountains you love but ride them the way you want at the same time?

Mountain bikers in Dorking – the south-east's premier spot for trails – have a battle on their hands. Europa Oil & Gas have submitted proposals for oil exploration on top of Leith Hill. It's a move that would severely restrict access to the area for cyclists and drastically increase the number of HGVs. It is hard to think this would be a good thing.

Yet on any given weekend, the carparks in the area are full of 4X4s, driven in from London and the surrounds so people can ride. Not particularly good for the environment. And often, tyre marks can be seen carving up tracks on which bicycles are banned, both for the safety of walkers and the preservation of the landscape. In other words, riding a bike doesn't necessarily make you a saint.

True, there are purpose-built trail centres like 7 Stanes in Scotland and Afan Forest in Wales, and there is great evidence of what can be achieved when mountain bikers and forestry commissions work together. But there is an argument that says if you only ever ride trail centres, you end up a rather cosseted and not particularly hardcore rider. Plus, nothing can beat the feeling of riding stunning scenery in the great, unbounded, outdoors.

So should mountain biking be limited more to trail centres, thus removing the freedom and imagination which draws a lot of people to the sport? Or should we just accept that some environmental damage is a rather horrible side effect of what is, in its essence, a really good way to spend a day?