Can tabbies thrive on carrots and onions and beans?

Dear EarthTalk: I don’t eat meat, for a variety of ethical and environmental reasons, and I’d rather not feed it to my cat, either. Do cats have to be carnivores?

John McManus

Needham, Mass.

Unlike dogs and other omnivores, cats are true (so-called “obligate�) carnivores: They meet their nutritional needs by consuming other animals and have a higher protein requirement than many other mammals. Cats get certain key nutrients from meat — including taurine, arachidonic acid, vitamin A and vitamin B12 — that can’t be sufficiently obtained from plant-based foods. Without a steady supply of these nutrients, cats can suffer from liver and heart problems, not to mention skin irritation and hearing loss.

As such, a cat’s ideal diet is made up mainly of protein and fats derived from small prey such as rodents, birds and small reptiles and amphibians. Some cats munch on grass or other plants, but most biologists agree that such roughage serves only as a digestive aid and provides limited if any nutritional value.

Of course, providing your domestic cat with a steady stream of its preferred prey is hardly convenient or humane — and cats can wreak havoc on local wildlife populations if left to forage on their own. So we fill them up on dry “kibble,� which combines animal products with vegetable-based starches, and meat-based canned “wet� foods, many containing parts of animals cats would likely never encounter, much less hunt and kill, in a purely natural situation. Most cats adapt to such diets, but it is far from ideal nutritionally.

Veterinarian Marla McGeorge, a cat specialist at the Best Friends Veterinary Medical Center in Portland, Ore., argues that the problem with forcing your cat to be a vegetarian or vegan is that such diets fail to provide the amino acids needed for proper feline health and are too high in carbohydrates that felines have not evolved to be able to process. As to those powder-based supplements intended to bridge the nutritional gap, McGeorge says that such formulations may not be as easily absorbed by cats’ bodies as the real thing.

Some would vehemently disagree. Evolution Diet, makers of completely vegetarian foods for cats, dogs and ferrets, says that its meatless offerings, on the market for 15 years, are healthy and nutritious, and, if anything, have extended the lives of many a feline and canine, even reversed chronic health problems. Claiming that most mainstream pet foods contain artery-clogging animal fat, diseased tissue, steroid growth hormones and antibiotics no less harmful to pets than to humans, its Web site posts testimonials from loyal customers who claim happy and long-living pets who look forward to their meals.

And Harbingers of a New Age, which makes “Vegecat� kibble and supplements that provide cats with nutrients otherwise only found in meat, says that its products allow owners to “prepare food in your own kitchen, choosing recipes that fit your lifestyle.�

The vegetarian pet debate is a contentious one among vegetarian pet owners and veterinarians and is one not likely to go away anytime soon. The best approach may well be to give some of the non-meat supplements and/or foods a try. If your cat won’t eat them, or does not do well on them — take kitty to a veterinarian for a check-up to see — you can always go back to what you were feeding her before.

Dear EarthTalk: What is the “green cities� movement?

John Moulton

Greenwich

Best described as a loose association of cities focused on sustainability, the emerging “green cities movement� encompasses thousands of urban areas around the world all striving to lessen their environmental impacts by reducing waste, expanding recycling, lowering emissions, increasing housing density while expanding open space, and encouraging the development of sustainable local businesses.

Perhaps the archetypal green city is Curitiba, Brazil. When architect and urban planner Jamie Lerner became mayor in 1972, he quickly closed six blocks of the city’s central business district to cars, delighting residents and business owners alike. Today the automobile-free zone is three times larger and serves as the heart of the bustling metropolis. Lerner also put in place a high-tech bus system, greatly reducing traffic, energy usage and pollution; the move also encouraged density around transit hubs and thus preserved open space in other areas that would have likely turned into suburbia. Today the bus system still goes strong, and three-quarters of the city’s 2.2 million residents rely on it every day.

Another green cities leader is Rekyjavik, Iceland, where hydrogen-powered buses ply the streets and renewable energy sources — geothermal and hydropower — provide the city’s heat and electricity. London, Copenhagen, Sydney, Barcelona, Bogota and Bangkok, not to mention Sweden’s Malmo, Ecuador’s Bahía de Caráquez and Uganda’s Kampala also score high for their green attributes and attitudes.

Green cities abound in North America, too. In 2005, Portland, Ore., became the first U.S. city to meet carbon dioxide reduction goals set forth in the landmark (if ill-fated) Kyoto Protocol, an international agreement forged to mitigate the threat of global warming. Seattle, Wash., also committed to meeting Kyoto’s goals and has persuaded 590 other U.S. cities to do the same under the U.S. Mayors Climate Protection Agreement. And Vancouver, B.C., draws 90 percent of its power from renewable sources while its metro area boasts some 200 parks and more than 18 miles of accessible waterfront.

San Francisco is a leader in green building, energy efficiency and alternative energy, and has been at the forefront of the battle to reduce plastic usage. Austin, Texas, is fast becoming a world leader in solar equipment production and has made great strides in preserving open space. Chicago has invested hundreds of millions of dollars revitalizing its parks and neighborhoods, and has built some of America’s most eco-friendly downtown buildings. It is also working to provide affordable clean power to low-income families. Of course, many would argue that New York City — with its densely packed housing, reliance on mass transit and walking, and recent green policy moves by Mayor Bloomberg — may be the greenest of all.

While there is no formal green cities organization, per se, many groups have sprung up to help urban areas achieve their sustainability goals. GreenCities Events, for one, hosts conferences around the United States at which local experts, policymakers and business leaders share ideas for greening their region. And International Sustainable Solutions takes urban planners, developers and elected officials on tours so they can check out some of the world’s greenest cities to glean first-hand what works and what can be applied back home.