[Sust-mar] How green is your pet?

Christopher Majka c.majka at ns.sympatico.ca
Sat Nov 7 09:22:03 EST 2009

Hi folks,

In an article published 23 October 2009 in NewScientist entitled "How  
green is your pet?", Kate Ravilious looks at the ecological impact of  
pets. The results of her research are fascinating. Part of the article  
is based on a recent book by Robert and Brenda Vale at Victoria  
University of Wellington in New Zealand, entitled "Time to Eat the  
Dog: The real guide to sustainable living."

The Vale's analyzed the ingredients of pet food and calculated the  
ecological footprints of pets. For example, a medium-sized dog  
consumes  about 164 kilograms of meat and 95 kilograms of cereals a  
year. It takes 0.84 hectares of farmland a year to generate that much  
food. For a large dog such as a German shepherd, the ecological  
footprint 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. So, a large dog  
has about 2.5 times the environmental impact of a gas-guzzling SUV!

Similar calculations show that the ecological footprint of a cat is  
0.15 hectares (slightly less than that of a VW Golf); a hamster's is  
0.014 hectare; a canary 0.007 hectares; and even a goldfish has a fin- 
print of 0.00034 hectares (3.4 square metres), about the same energy  
usage as two cellphones.

The United States, which tops the list for cat and dog ownership, is  
home to over 76 million cats and 61 million dogs. Taking the estimated  
cat population of the top 10 cat-owning countries, the Vales  
calculated that the land required just to feed these cats is over  
400,000 square kilometres. That's equivalent to 1.5 times the area of  
New Zealand. A further five New Zealands are required to feed the dogs  
found in the top 10 dog-owning countries!

Ravilious also examines other effects of pet ownership. For example, a  
recent article (Mammal Review, 2002, volume 33, page 174) indicates  
that cats annually kill 188 million wild animals in Great Britain,  
i.e., circa 25 birds, mammals, and frogs per cat per year (and surveys  
in Australia and the United States have shown similar numbers). Also,  
cat excrement is particularly toxic. In California a decline in sea  
otters has been linked to a brain disease caused by the parasite,  
Toxoplasma gondii. It is found in cat faeces and ends up in rivers due  
to cat owners who flush their cat litter down the toilet or allow  
their cats to defecate outside. Dolphins and whales have also been  
affected [this is from a study by Gloeta Massie and Michael Black  
presented in 2008 at the annual meeting of the American Microbiology  

Dogs also cause problems by disturbing wildlife in wild areas where  
they are allowed to run off-leash. In Australia  Peter Banks and  
Jessica Bryant of the University of New South Wales (Biology Letters,  
volume 3, page 611) showed that areas frequented by dogs had 35 per  
cent less avian diversity and 41 per cent fewer birds overall compared  
to areas where dogs were not allowed. Studies in Great Britain link  
the decline of some species of birds, such as European Nightjar  
(Caprimulgus europaeus), to disturbance by dogs (The Ibis, volume 149,  
page 27).

A quick calculation I did from some of the data in the article shows  
that the ecological footprint of an average person in Great Britain is  
is ~ 7.5 hectares/year. Thus, a large dog would comprises about 15% of  
that value. David Mackay, the United Kingdom government's new energy  
adviser is quoted as saying, "If a lifestyle choice uses more than 1  
per cent of your energy footprint, then it is worthwhile reflecting on  
that choice and seeing what you can do about it."

The full NewScientist story is available at:




Christopher Majka  <c.majka at ns.sympatico.ca> | Halifax, Nova Scotia,  

* Research Associate: Nova Scotia Museum | http://museum.gov.ns.ca/mnh/research-asfr.htm
* Review Editor: The Coleopterists Bulletin | http://www.coleopsoc.org/
* Subject Editor: ZooKeys | http://pensoftonline.net/zookeys/index.php/journal/index
* Associate Editor: Journal of the Acadian Entomological Society | http://www.acadianes.org/journal.html
* Editor: Atlantic Canada Coleoptera | http://www.chebucto.ns.ca/Environment/NHR/atlantic_coleoptera.html

"Whenever I hear of the capture of rare beetles, I feel like an old  
war-horse at the sound of a trumpet." - Charles Darwin

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