Their most startling conclusion is that dogs are significantly more damaging to the planet than SUVs.

The authors claim that keeping a medium-sized dog has the same ecological impact as driving a 4.6 litre Land Cruiser 10,000km a year.

They use a rather unusual method of calculating environmental impact.

Instead of measuring emissions of CO2, or CO2 equivalent, they calculate the literal footprint or "global hectare" (gha) - the amount of land it takes to support a given activity.

So they work out that constructing and driving the Land Cruiser for a year takes 0.41 gha.

Growing and manufacturing the 164kg of meat and 95kg of cereals a border collie or c*** spaniel eats every year takes about 0.84 gha.

A bigger dog such as a German shepherd consumes even more - its pawprint is more like 1.1 gha.

By their reckoning, that is more than the environmental footprint of the average Indian person, who uses just 0.8 gha of resources.