TAILIEUCHUNG - Perlman - Practical Ecology for Planners, Developers and Citizens - Chapter 2

2 An Introduction to Ecology and Biodiversity Southeastern Arizona is one of the most beautiful parts of North America, with stunning deserts interspersed among pine-covered mountain ranges. The watershed of the San Pedro River, undammed along its entire 140-mile. | I 2 An Introduction to Ecology and Biodiversity E Southeastern Arizona is one of the most beautiful parts of North America with stunning deserts interspersed among pine-covered mountain ranges. The watershed of the San Pedro River undammed along its entire 140-mile 225 km length stands out in this landscape for its exceptional biological richness see Figure 2-1 . In fact this watershed of 3 700 square miles 9 600 square km is arguably as biologically rich as any region of its size in the continental United States or Canada with almost 400 species of birds 82 species of mammals and 43 species of reptiles and amphibians all in an area smaller than By comparison the entire United States contains just 768 bird species 416 mammal species and 514 reptile and amphibian The San Pedro watershed may be the most sought after spot in the United States by bird-watchers and it is widely recognized among biologists as a jewel. But what does it mean to say that an area is biologically rich And once we determine that an area is biologically important then what Biodiversity The Stuff of Life Biodiversity is the term used by conservation biologists to describe the entire diversity of life encompassing all of the species genes and ecosystems on earth or within a given area as in the biodiversity of the San Pedro River watershed .3 In practice biodiversity is sometimes measured simply by counting the number 22 HUMANS NATURE AND INTERACTIONS Figure 2-1. The San Pedro River of southeastern Arizona is undammed along its entire 140-mile 225 km length. This is a perennial stretch of the river that runs year-round. of species found in an area known as the area s species richness as in the brief description above of the San Pedro s biodiversity. However a more precise measure would also consider the number of different ecosystems present as well as the genetic diversity found within individual species. In addition community structure the proportions and arrangements of

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