Growing cities are not homogenous places.  Diversity is an essential part of the makeup a city. There are two distinct and important meanings to diversity in cities, social diversity and cityscape diversity.

Social Diversity (Diversity of People)

If variety is the spice of life, then diversity is the spice of cities.  Social diversity includes diversity of thought, religious beliefs, races, sexual orientation, educational background, income, and every other way that demographers measure how we divide ourselves up. The strongest cities embrace and capitalize on their diversity.

People want to live in cities where there is diversity.  Recent studies by researchers such as Richard Florida show that young people want to live in cities where gay and lesbian people are accepted. The reason is not as much that they want to live near gays and lesbians, or that they like gays and lesbians any more than they like anyone else.  The reason is that they believe that if a city is accepting of gays and lesbians, they will be accepting of me as well.

Cityscape Diversity (Diversity of Place)

Diversity in cities goes well beyond social diversity. Jane Jacobs has pointed out that cities need to be interesting places to be, with mixture of architectural types and buildings of all shapes and sizes. To people walking on the street, a variety of buildings, trees, and a variety of businesses make for a rich, interesting city space.

Diversity makes life more interesting. Life is boring if every building looks the same. Life is even more boring if every person looks the same, believes the same, and has the exact same background.