Andrew Laxon reports in the final of a five-part series on ethical shopping
Can my weekly shopping list really help save the world?
In theory yes, because if people refuse to buy products which damage the environment, companies will have to change their production methods to stay in business. One of the best-known examples occurred in 2009 when Cadbury started using palm oil in its chocolate bars. Much of the world's palm oil comes from Malaysia and Indonesia, where the rainforest habitat of endangered orang-utans is cleared to grow the crop. After a consumer revolt, which included Auckland Zoo taking Cadbury bars off its shelves, the company reversed its decision.
How do I know when a product is good or bad for the environment?
Look for hard evidence, preferably a rating from an independent agency, says Consumer research writer Jessica Wilson, and ignore meaningless claims like "sustainable" or "eco-friendly".
This may involve some online research before you reach the supermarket but there are some handy cut-out-and-keep guides. One is the Best Fish Guide produced by Forest and Bird, which includes a colour-coded ranking list from "best choice" (skipjack tuna, blue cod, trevally) to "worst choice" (snapper, southern bluefin tuna, orange roughy). In response to customer complaints about tuna-catching methods, Foodstuffs (Pak'n Save, New World, Four Square) made its Pams brand of tuna "FAD free" last year. This means the fish was caught without the use of "fish aggregation devices", which lure large schools of tuna to one spot and then scoop up everything in giant nets - killing turtles, sharks, juvenile fish and other wildlife in the process.
Is it better to buy local?
Sometimes but not always. The latest fad in Britain is "food miles", which calculates the distance food has travelled to reach your plate and therefore its production of carbon emissions. Some British supermarkets even put warning labels on air-freighted food, although to the horror of New Zealand exporters who say food grown here has a lower carbon footprint than energy-inefficient British farming.
Former Green MP and food campaigner Sue Kedgley agrees the food miles argument often doesn't stack up but says if we don't buy local food we will lose it. "We had a flourishing garlic industry, in came the container loads of cheap Chinese garlic ... and there's only four or five hanging on in Martinborough."
Shoppers who want to buy local face a trade-off between price, patriotism and possibly taste. For instance, an 820g can of Budget peaches from China cost $2.15 at New World last month, less than half the $4.49 price for the same size can of Watties Hawkes Bay peaches, marketed as "New Zealand grown".
Are there more environmentally friendly alternatives?
You may find more sustainably produced food at places like organic stores and farmers' markets but driving from store to store in a gas-guzzling SUV will not help and few people have the time or money to do most of their shopping like this. One carbon-reducing tip is online supermarket shopping, which works well for clearly defined, short lists. You can also order home deliveries of fruit and vegetables, which provide fresher, better tasting food for about the same price as supermarkets. Although you don't choose the food, you can say no to things you don't like.
If you're serious about saving the world, consider eating less meat and fewer dairy products, which require far more resources than plant crops. A 2010 United Nations report called for a shift towards a vegan diet, saying Western tastes were unsustainable.