What's the one lifestyle change I could make that would have the most positive environmental impact?

B Levy, by email

First, many thanks to all those who have already responded to this chewy, yet rather fascinating subject. There is a fantastic range of answers and arguments below which prove just how tricky this question is to answer definitively. In fact, the responses to date prove quite comprehensively that there is no single-answer response, although I think it is very telling just how often the issues of rearing children and eating meat have come up during the debate. Is this because they are so emotive, or because they really are up there as the most important issues? A bit of both, I like to think.

I have actually tackled this question before, albeit with a subtly different focus. Three years ago, I was asked: "If I was to do just one thing to help combat climate change, what should it be?"

As with now, some similar themes came up when I went searching for answers. To summarise: cars, babies, steaks and boilers. But there are some additional suggestions below which I think deserve equal attention. For example, GreenerTogether makes the simple point:

Think before you buy anything! Social, economic and environmental impacts.

The "buy less" theme seems popular, as does the "fly less", but I was particularly interested by the response of FC1967 who displayed a real sense of weariness that the self-sacrifice message just doesn't cut it with many people. No real surprises there, I guess, but I thought the concluding point was telling:

The one big change, and the only one that will really make a difference, is to become an environmental activist. Everyone with a conscience should be campaigning at least 10 hours a month.

In the search for more insight, I decided to put B Levy's question to some other interested parties. Again, it's interesting how varied the answers are. First, here's what a Greenpeace spokesperson had to say:



The answer to this question obviously differs from person to person and family to family, depending on what their lifestyles already involve. But for many people the single biggest and most simple way to reduce their emissions will be to reduce flying. Britons already emit more per capita from flying that any other nation on Earth, so there's a lot of room for reductions. People who saw Age of Stupid [an eco documentary] will remember the family with the carbon calculator realising that by taking the train instead of flying they made a real difference.

Friends of the Earth takes a somewhat different tack. As with FC1967, it believes "getting active" is the most profound single step you can take:



Lifestyle changes are important. We should all do what we can to minimise our environmental footprint. It also signals to politicians that we are serious about treading lightly on the planet. But if people want to know the one thing they can do to we want to make the most positive environmental impact Friends of the Earth's advice would be - get active! Friends of the Earth's campaign for a new climate change law - The Big Ask - highlights the success of people power. Over the course of the three-and-a-half year campaign nearly 200,000 spoke to their MP directly - by letters, email, posting a video clip, or in person, calling for a tough new law to tackle climate change. As a result, a new law to slash UK emissions by at least 80% by 2050 was passed in October 2008 - the first national legislation of its kind anywhere in the world. This prompted Nick Robinson, BBC political editor to say: 'People often ask: "Does anything change politics?" Well it has here.' There are lots of issues to get active around. Friends of the Earth is currently running campaigns for the new government to tackle international greenhouse gas emissions, stop deforestation caused by the UK's dependence on imported feeds for factory farmed meat and dairy and to ensure that local councils play their part in cutting carbon.

I also sought the views of the Energy Saving Trust. It said:

Energy Saving Trust believe that everyone can and should make more than one lifestyle change, to help lower our carbon footprint. As we are experts within the home we recommend insulating and driving less, because if everybody took this up then there would be no/very few negative environmental effects. Ditching the car for a year could save around three tonnes of CO2 per year, on average. Installing solid wall insulation could save two tonnes CO2 per year. Replacing your oil central heating with a wood fuelled boiler – 4.6 tonnes of CO2 saved per year providing wood fuel is locally sourced. (All these are based on average or typical behaviours/house types.)

For a different angle, this pie chart may help. From the issues we deal with, transport and space heating are the actions which produce the most CO2 (transport not included on this chart below). Therefore, insulating your house as best as possible to reduce heating needs will have a huge impact on CO2 emissions.



However, personally, I think my favourite response so far has been from BeinnSgritheall. I think just the simple act of talking about these issues with other people is one of the most important agents for change:

Change the minds of those around you. Discuss, argue, debate. Make this a tea break, dinner-table discussion. I suggest that those responding to this article are already doing more than the average - the crucial thing is bring others doing little or nothing into the debate. Everyone I know seems to have a Daily Mail-informed sceptic or denier in their family - but few seem prepared to broach the subject. Yet we can, over time, change the prevailing social mores - smoking being a key example. That should be our aim, one chat at a time.

• Please send your own environment question to ask.leo.and.lucy@guardian.co.uk

On 10 May Leo originally wrote:

It's time to roll up our collective sleeves and face one of the trickiest questions of them all.

Given the variables in all our lives - geography, income, age etc - it's hard to see how we could ever settle on one definitive answer, but let's at least give it a go. Is it ditching the car? Having fewer, or no, children? Eating less meat? Installing solar panels? Living in a smaller home? Donating money to an environmental charity? Participating in direct-action protest? Er, voting for change? The list is long. As always, please share your thoughts and I'll return to join the discussion on Friday.