momoe, this, which I just read, should interest you as well because it's an intersection of this topic with the "availability of fresh healthy food" topic:

Rural Kenyans Are Bringing Their Cows With Them to Cities. What Could Go Wrong?
One of the stranger aspects of Africa's rapid urbanization is the influx of livestock in new, unplanned towns -- and the diseases they bring with them.
By Olga Khazan, The Atlantic, Apr 7 2013

[....] the people who are moving to cities aren't entirely leaving their rural lives behind. Instead, they are bringing their livestock with them, often keeping them right in their backyards, even in densely populated areas.

As a result, low-income countries have started to see a dramatic spike in a class of disease known as zoonoses, which pass from animals to humans. These can cause everything from tapeworms to fatal diarrhea, and they're concentrated near major cities in Africa and India.

A recent study by the International Livestock Research Institute found that zoonoses make up 26 percent of the infectious disease burden in low-income countries, but just 0.7 percent in high-income countries.

Now, researchers are beginning to trace these ailments to the livestock that sleep just over the windowsill from the residents of the developing world's newest cities.

In Dagoretti, one in 80 people keep cattle, and 60 percent of households have poultry. A typical house there might have a shed full of rabbits or chickens under the bed. A cow kept in the yard may graze by the roadside or munch potato peels from a local eatery.

But animals and cities don't always mix well. Throughout history, as cities modernized and developed, any lingering livestock were soon banished to the countryside.

That's not an option for people in places like Dagoretti, where there are still very few grocery stores, and low incomes mean many residents rely on raising and selling their own food. For the town's infants and children, the nutritional benefits of ready access to milk outweighs some of the cow-related drawbacks.

"In cultures where you don't do fridges or freezers, there's a huge demand for milk and meat and it needs to be close to where it's eaten," said Delia Grace, a Nairobi-based researcher for the International Livestock Research Institute.

A cow can also be used as collateral for those lacking the money to get bank loans.

"You can use the cow as surety. With a cow, you can leverage funds, you can get a loan," Grace said.

For these and other reasons, Dagorettians won't -- and probably shouldn't -- get rid of their cows and other animals.[....]

"Locavorism" runs into more obstacles as far as environmental consideration? Gets into all kinds of though provocation, such as: is continued urbanization of the human population good or bad for the environment on the balance?