A、Consumer class rises in developing countries. B、Four-footed livestock are easier to raise. C、Farm animals often provide nutrie

As the world population rises, the demand for meat, eggs and dairy products is soaring in developing countries. The Worldwatch Institute warns that without safeguards the demand could strain the environment and pose public health risks.
    Over the last 30 years, the number of farm animals—and that includes both four-footed livestock like cattle, pigs, goats and sheep, as well as poultry, like chickens—has increased about 23 percent. So now we have about 20 billion farm animals worldwide.
    There are two main reasons for the increase. First, it is the urbanization and rising incomes particularly in developing and emerging countries. China, Brazil, India—they’ve all seen their middle class or consumer class rise over the last 30 years. And what tends to happen when people have a little bit more money to spend is they spend it on higher quality food. They tend to buy more milk or cheese or meat.
3 What is the possible consequence of increasing demand for meat?
4 Why does the number of farm animals increase?