3 When Humans and Nature Collide Imagine Exponentia, a booming city of the early twenty-first century. A hundred years ago, Exponentia was a town of barely 5,000 residents; today, it has more than 100,000, with most of that growth taking place in just the last half-century. | 3 When Humans and Nature Collide Imagine Exponentia a booming city of the early twenty-first century. A hundred years ago Exponentia was a town of barely 5 000 residents today it has more than 100 000 with most of that growth taking place in just the last half-century. A large proportion of the city s residents have high-tech jobs and many of them appreciate the easy access that the city has historically had to beautiful natural areas. As a result of its recent growth however the town-become-city now extends well out into the neighboring farmlands rangelands and mountains and has become part of a larger metropolitan complex see Figure 3-1 . Exponentia is fictional but cities like it can be found across North America as you read the next few paragraphs imagine your local version of Exponentia and fill in the relevant details. Planners are familiar with many of the human challenges that accompany rapid growth such as the need to fund additional roads schools public safety services and water and sewer infrastructure. But how does urban growth affect native species and habitats The most obvious effect of the city s expansion is the loss of native habitat. This is a zero-sum game with three players natural habitats agricultural lands and urban land uses. As one land use expands typically human-inhabited areas one or both of the others contract. Granted these are not completely mutually exclusive categories for example lightly used rangelands and sparsely inhabited regions can serve as good habitat for some native species. But by and large every acre of the landscape can be assigned to one or When Humans and Nature Collide 37 another of the categories and the unmistakable trend and one that shows no sign of changing is that native habitat has been shrinking over time. As the four diagrams of Exponentia shown in Figure 3-1 illustrate human development is not likely to occur in all areas equally. Development proceeds rapidly on relatively flat sites with well-drained soils
