The teeth sucked, the cynics scoffed, the Cassandras said it could be the company's downfall, but Marks & Spencer's decision this week to spend £200m over the next five years to green up the biz may be the most astute move yet from chief executive Stuart Rose. The company says it intends, within five years, to become "zero carbon" selling only ethically produced clothes, reducing waste, recycling everything and cutting back on transport. This marks it apart from the rest, but the reality is that big business now has no alternative but to change course, both to keep its markets and to make money. M&S are only doing what everyone else is bound to do in time.

Here's why:

1. Green is where the new money is. Carbon looks like becoming a parallel currency as the EU emissions trading scheme kicks in and the Kyoto treaty is reworked after 2012 to being in China and India, Brazil and Mexico. UK companies with low emissions will be at a significant advantage over those who have failed to act.

2. The price of energy is certain to rise in the medium and long term. All major oil and gas companies are chucking billions of dollars at finding new fields but none are replenishing their reserves as they used to. On top of that, most of the world's oil regions are increasingly volatile, the demand for energy resources is growing as countries like China and India develop. A far-seeing business acts now, before the full effects of inevitable price rises filter in.

3 Waste, which is a large part of the retail business, is going to be taxed more and more heavily. The days of big stores dumping rubbish in landfills is over. EU rules mean that from now on, every tonne chucked out is going to cost many hundreds of pounds. M&S have taken advice and see a way for their waste to become a resource, either as compost or as a raw material for the plastic or paper industries.

4 Green is now mainstream in Britain at least and any business that doesn't switch runs the risk of looking stupid and old fashioned. The consumer actively demands Fairtrade and higher standards of food and commodity production. The biggest profits are to be made on higher value organic and Fairtrade products are coming down as they become more mainstream, and the companies that move first can benefit the most.

5 It's not very difficult. All the technologies that M&S intend to use are tried and tested, and indeed the company has trialled quite a few already. Plastic bags can be made to biodegrade, packaging can be simplified, the organic, Fairtrade cotton market is booming, clear labelling is a doddle, bio-gas can be generated from composted fruit and vegetables, energy costs can be reduced.

It's not a revolution, but it's state of the art and probably the most comprehensive plan that any of the big supermarkets has come up with yet. Watch the others run to keep up.