Spain would need seven times as much woodland as it currently has in order to absorb all the carbon dioxide emitted annually, 11% of which comes from car exhausts.

This is the conclusion reached by the RACC in a recent report on the effects of cars on the environment, which proposes a 'decarbonisation' of cars via the tax system in order to reduce their impact on the environment and improve the country's air quality.

The president of the RACC, Miquel Nadal, outlined the results of the study in a press conference today and underlined the urgency with which the country need to act, maintaining that it was still possible to do something and that 'being green' would be worthwhile in the end.

CO2 emissions in Spain rose by 90% between 1990 and 2006,  partly as a result of the increase in cars on the road.  This increase is well above the 50% world average, far greater than the 15% laid down for Spain in the Kyoto agreement.

Thanks to technological advances, the majority of cars currently being sold in the European Community produce approximately 30% less contamination per kilometre now than they did 30 years ago, but the study criticises the continued dependency on petrol, which 95% of road transport uses.

Estimates suggest that in 30 years time the 900 million cars currently on the world's roads will have risen to 1,800 million, equating to a huge increase in demand for petrol, which will be in ever-shorter supply and therefore more and more expensive.

Nadal argued in favour of investment in the development of hybrid cars, which could reduce petrol consumption by 50% over the next 15 years and, above all, in electric cars, which would reduce CO2 emissions by 70%.

Apart from encouraging the use of public transport, motorbikes, bicycles and, of course, people using their own two legs, Nadal wants to see 'green driving' taught as part of the driving test so that new drivers learn to drive in a more fuel-efficient way.