As well as having a love affair with oil as fuel for cars, New Zealanders have a love affair with oil - in the form of plastic shopping bags.

We use 800 million bags each year which works out at around 200 bags per head per year.

Plastic bags are a major and growing environmental concern in New Zealand and around the world.

Plastic bags made of polyethylene take hundreds of years to decompose. They waste oil; litter waterways, beaches and reserves; pose a threat to wildlife, especially marine life; fill landfills unnecessarily; and release toxic gases when burnt.

In Bangladesh, plastic bags blocking drains have caused severe flooding during monsoons. In the once pristine Himalayas, plastic bags flutter over the foothills. Marine animals (especially turtles) and birds are killed by plastic they mistake for jellyfish and squid.

A minke whale washed up on a beach in northern France had 800kg of plastic bags and other packaging in its stomach.

Discarded plastic bags have become so common they have acquired nicknames: in South Africa they are roadside daisies, in China white pollution and in Ireland witches' knickers.

In New Zealand plastic bags litter our coastal, rural and urban environments. They also endanger marine life, including the rare Hector's dolphin.

Plastic-bag pollution also undermines the clean, green image promoted to tourists and the bags contribute to our trade deficit as 90 per cent of them are imported.

In order to reduce these negative impacts it is necessary to address the problem of excessive use. The good news is that, unlike some other environmental problems, the solutions are simple.

Humans are degrading and destroying most of the earth's natural ecosystems, so anything we can do to reduce pressure on the ecological systems that support life has to be a good thing.

Several countries have taken action to tackle plastic-bag pollution. Ireland introduced a tax on plastic bags in 2002 and this has reduced their use by more than 90 per cent; the UK is thinking of following suit.

In Canada, most supermarket chains collect bags for recycling. In 2002, Bangladesh banned plastic bags because they were clogging drains and increasing the risk of flooding, and introduced a $15 on-the-spot fine for using a plastic bag. Many other countries are taking steps to reduce plastic-bag use and find alternatives that are cheap and practical.

Some say the answer lies in biodegradable plastic bags - e.g. ones made of natural polymers such as cornstarch, cellulose and calcium carbonate. If there were more restrictions on the use of plastic, it is possible new technology could play a large part in solving the problem.

However, there are problems with some bio-plastics as they don't always decompose properly or quickly enough. Some alternative products break down into flakes which can harm wildlife, and a degradable bag looks as much like a jellyfish to a dolphin as a non-degradable one.

Recycling is another option. Some New Zealand supermarkets collect plastic bags for recycling, but perhaps they need to do more to advertise this and actively encourage recycling.

The Christchurch City Council collects plastic shopping bags as part of its recycling collection and they are turned into plastic planks for pallets and boxing. It would help if more councils collected and recycled plastic bags in this way.

Manufacturers could also be required to have a minimum amount of recycled material in plastic shopping bags.

New technologies and recycling initiatives are, however, no substitute for reducing our over-use of plastic bags in the first place. Once people are aware of the negative environmental impacts of plastic bags, they often look for alternatives.

Consumer education and campaigns can do much to raise awareness of the problems and encourage shoppers to change their habits. In Ireland, for example, the public overwhelmingly supported a levy on plastic bags. After the levy was introduced there was an immediate and dramatic reduction in the use of plastic shopping bags.

In New Zealand, Pak'nSave's 10c charge for each bag has also resulted in shoppers making less use of plastic bags.

Even without a levy, it's possible to achieve dramatic changes in consumer behaviour.

Consumer education by the Golden Bay Bag Ladies - a group of women concerned about plastic bag pollution in their area - has reduced plastic-bag use in Golden Bay by 50 per cent.

Most people know plastic bags are a problem, are concerned about it and just need a little encouragement to reduce their own use. So what are some of the alternatives?

Cloth bags, designed by the Auckland Waste Managers Forum, are available in many supermarkets, and all the councils in Auckland sell these bags through their council offices and libraries. The bags are made out of unbleached cotton.

The Green Bag Foundation also provides an alternative in the form of the Green Bag which is made from recyclable materials. Ten cents from each bag sold goes towards supporting community groups which are involved in waste-minimisation projects.

You can also reduce your use of plastic bags by asking checkout operators to put more items in one bag or refusing bags for items that already have their own wrapping, e.g. nappies and bags of apples.

Shopping can also be loaded from shopping trolleys into a cardboard box or laundry basket and from there unloaded into the kitchen.

Solutions for New Zealand include raising awareness of the issues, introducing a levy on plastic bags supplied by shops, requiring bags to have a minimum amount of recycled material, supporting the development of bio-plastic materials and encouraging use of sustainable alternatives such as paper bags, cotton bags, the Green Bag and boxes.

Most of these positive measures to tackle excessive plastic-bag consumption are possible, practical and cheap. We can all make simple choices that still allow us to meet our own needs without damaging our environment. Start today.

* Cathy Wright is a freelance researcher and writer.