In a world with an ever-growing population and ever-scarcer resources, the sight of shoppers in supermarkets taking a fresh plastic bag for every three or four items of shopping has become increasingly jarring.

That phenomenon is likely to become a thing of the past from today, however, thanks to the implementation of a new law introducing a 5p charge for single-use carrier bags, regardless of what the bag is made of.

The move is eminently sensible. Councils collect around 7.4 million plastic bags every year which end up in landfill. The vast majority need not have been required. Many more litter the countryside, waterways and seas. The tragic sight of seabirds with plastic bags caught around their legs, seals and dolphins with them around their necks and turtles with bags trailing from their mouths (they mistake them for jellyfish), should make every one of us stop and think. Large marine animals such as whales that accidentally swallow plastic bags are apt to suffer a slow death as the plastic causes twisted obstructions in their guts. If a 5p charge on a carrier bag can prevent even some of that unnecessary suffering and death, it is well worth it.

A 5p charge will bring about a change of behaviour among consumers by encouraging people to ensure they always have the means to carry their shopping with them. No sensible person would go out on a blustery day without an umbrella or raincoat; if they did, they would blame themselves for being caught in any downpour. Now all shoppers in Scotland will know if they do not have a bag with them, they will be charged to buy one. It is safe to assume that will concentrate many minds.

The proof of how effective such charges can be in reducing bag use comes from other nations that have already introduced the practice. In Wales and Northern Ireland,single-use carrier bag use has reduced by around three-quarters.

This is a measure whose time has come. A charge on carrier bags was first mooted in 2005 by the then Liberal Democrat MSP Mike Pringle, but his bill was defeated because the Scottish Executive, under pressure from business groups, said the benefits were unproven. That can no longer be said. In the nine years since, there has also been a cultural change, reflecting a growing sense of responsibility among consumers towards the environment.

Recycling has become the norm in most households, "reuse" websites such as Gumtree have revitalised the trade in second-hand goods and austerity has led consumers to appreciate as never before the happy coincidence between preserving the earth's resources and saving money.

It is a neat feature of the law that monies raised from the charge will go to charity. Paradoxically, the hope must be the scheme does not prove too lucrative for charities - if it does, then the charge will not be working effectively as a deterrent to bag use.

This measure has the capacity to bring about significant positive change with no discernible negative impact on the public and, as such, is overdue.