What’s your pet’s “carbon pawprint”?

New Scientist has a thought-provoking article about work by Robert and Brenda Vale, two architects who specialize in sustainable living at Victoria University of Wellington in New Zealand and who have looked into the ecological impact of pets. Apparently keeping a dog can be worse for the environment than running an SUV:

They calculated, for example, that a medium-sized dog would consume 90 grams of meat and 156 grams of cereals daily in its recommended 300-gram portion of dried dog food. At its pre-dried weight, that equates to 450 grams of fresh meat and 260 grams of cereal. That means that over the course of a year, Fido wolfs down about 164 kilograms of meat and 95 kilograms of cereals.

It takes 43.3 square metres of land to generate 1 kilogram of chicken per year – far more for beef and lamb – and 13.4 square metres to generate a kilogram of cereals. So that gives him a footprint of 0.84 hectares. For a big dog such as a German shepherd, the figure is 1.1 hectares.

Meanwhile, an SUV – the Vales used a 4.6-litre Toyota Land Cruiser in their comparison – driven a modest 10,000 kilometres a year, uses 55.1 gigajoules, which includes the energy required both to fuel and to build it. One hectare of land can produce approximately 135 gigajoules of energy per year, so the Land Cruiser’s eco-footprint is about 0.41 hectares – less than half that of a medium-sized dog.

I have an iguana (who is vegetarian) so from the point of view of her food her environmental impact is pretty minimal. But just the other day I was doing some back-of-the-envelope calculations that suggested she’s responsible for a quarter to a third of our household electricity consumption, because of the heat lamps that have to be on day and night for her. I’d imagine she’s still not as bad for the environment as an SUV — or a dog — but once she passes away I won’t be getting another reptile.

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