It is human nature to grieve over the conversion of beautiful open space into a concrete laden conglomeration of strip malls, housing developments, streets and dubious architecture.
Even when the land in question is of no use for farming or grazing, the encroachment of built up civilization signals a destruction of natural vistas, habitat, and the general idea of untouched and beautiful lands where animals and people can roam free in nature.
There are also concerns about air pollution, the massive waste that people generate, and the massive amounts of water and power that is needed to run even one household, let alone thousands of households. There are concerns about the crime, demands for services and social costs that will increase when the population increases exponentially.
Many criticisms are dealt with or are excessive, given the advancements in urban and suburban planning technologies, models and processes. There are extensive reviews of the environmental consequences of destroying habitat for wild animals and creating habitat for humans and pets. There are requirements for planting trees and shrubs in places that would otherwise be dead zones. There are requirements for open spaces, lakes, ponds, well protected waterways and wetlands, and grassy areas that either maintain existing habitats or create new habitats for animals, insects and birds.
There are benefits to allowing competition for housing that brings down the congestion and the cost of housing for humans. People who would not be able to afford an apartment or home in the cities can find suitable living in the "urban sprawl" that accommodates their incomes. The same critics who are overjoyed at looking at miles of pavement, concrete and towering structures are in awe of the low building profile, closer relationship with nature and organization of the suburban and outlying areas.
From a distant freeway, a housing development might look like a crammed together mass of housing, with no space between tens of thousands of structures. In fact, there are many areas of park and recreation space, permanently protected open spaces, apartment grounds, and backyards that simply do not exist in the cities.
From a distant freeway, a person will not see that land that may have been shrub and grassland is now conditioned and improved to support millions, if not billions of newly planted trees, grasses and ornamental plants that otherwise would not have survived. These plantings and soil conditioning provide healthy, new habitat for an incredible array of bird, mammal and insect species, as well as the microscopic forms of life. In other words, habitat that is lost can result in even better habitat that is gained when solid planning is allowed to happen.
The serious criticisms involve waste generation and management as well as the dependency on fossil fuels for transportation, moving water and for powering homes. It will take much more aggressive work in developing affordable electric vehicles, along with wind, solar and other forms of power generation for the existing and future urban sprawl to be tolerable.
The serious criticisms, however, do not consider that urban sprawl is not unplanned and has not been unplanned for a long time. Suburban communities tend to be self contained, meaning that services, schools and shopping exist with in a very compact area, which cuts the need for a lot of transit into the cities or regional centers. If public transportation gets the attention that it deserves, there will be ways for people to commute to work and to get around without driving fossil fuel powered cars. If electric vehicles become affordable, there will only be a need for power that charges the batteries.
Finally, waste management is now a cultural norm that involves personal habits and values of energy and water conservation, recycling, reuse and resale. Many non urban dwellers understand that it is now everyone's role to manage waste and trash.
In summary, urban and non urban planning is an art and science that exists to deal with criticisms about urban sprawl. Urban sprawl often creates or sets aside plenty of viable and healthy natural habitat. Urban sprawl allows people to get housing that is within their ability to pay, and it is a suitable alternative to milliions of people attempting to change to full rural living, where there is simply not enough land for everyone to own 20 acres for each household!