Lying in our tent in France one hot night last summer, I found myself musing, like I always do when camping, on how little it was possible to live on during a holiday and how much stuff I had back home. What was it all for? Might it actually be possible, like in films, to pack your whole life into one duffel bag - and if you did, what would your carbon footprint be like?

A group of American students recently helped answer that question. The class, at Massachusetts Institute of Technology, compared the lifestyles of Americans from all walks of life, from the ultra-rich like Oprah Winfrey right down to the homeless. They found that the average American's personal carbon footprint is 20 tonnes.

Much of it was accounted for by personal lifestyle choices, but even Americans with the lowest energy usage account for more than double the average global per capita carbon emissions, due to their share of public services and infrastructure like policing, roads and an energy-hungry military. The floor below which nobody could reach was 8.5 tonnes.

But the baseline carbon cost of public services is far from fixed: it is an area where big strides are being made and, with public pressure, greater improvements are possible.

In the UK, the average carbon footprint is a good bit less than in the US - nine to 12 tonnes, depending on which estimate you choose - but the issues are broadly similar. WWF, which prefers to deal with the more all-encompassing measure of the ecological footprint, estimates we in Scotland are living a three-planet lifestyle - using resources at three times the rate the earth can replenish them. We must get that down to one or below if it is to be sustainable. Three-quarters of our eco footprint is accounted for by the choices households make, but we can also influence the carbon cost of public services.

According to Elizabeth Leighton, WWF Scotland Footprint Policy Officer, much work is already being done on reducing environmental impact across public services. "Most councils have gone through a carbon management programme, but some really go-ahead ones like Fife are going further, holding managers to account for carbon emissions in their area," she says.

And with the recent consultation on the Climate Change Bill, which prompted a massive response, there is now the real prospect of legislative changes such as statutory targets of at least 3% year-on-year reductions in greenhouse gases, with an overall target of an 80% reduction by 2050. The carbon impact of public services might seem to belong in the box marked "government responsibility", but public pressure is the greatest agent of change.

Take it further: write to your local councillor, asking to know the carbon footprint of the council's operations and what is being done to reduce it.

To get involved, visit www.wwf.org.uk/core/about/scotland.asp.