Biodiversity: Concept, Measurement, and Challenge

In this chapter, you will learn about:

• 1. The concept of biodiversity

• 2. Methods of measuring and valuing biodiversity

• 3. Factors that affect levels of biodiversity and global patterns of species abundance

• 4. Preserving and managing biodiversity

Reflecting on conservation biology’s beginnings, Michael Soulé realized that the major factor in conservation biology’s emergence as a distinct discipline was the recognition among biologists of the accelerating and global loss of species – the “extinction crisis” (Soulé 1986). This shift in focus from the problem of “endangered species” to the problem of “loss of biodiversity” might sound like an exercise in biological semantics, but the change in emphasis is significant. Conservation biology’s historical origins were in applied sciences such as forestry, wildlife management, fisheries, and range management (Chapter 1). Such disciplines, emerging as distinctive professional communities from the 1930s through the 1950s, were traditionally species- specific in their approach to management and their understanding of species’ values. In this environment, studies of species’ natural history and habitat requirements received priority. Resource management disciplines began to influence environmental law in the 1960s and 1970s, and the legislation drafted in this period reflected a similar emphasis. The US Endangered Species Act (Chapter 3), with its emphasis on individual species as the primary targets of conservation efforts, is the best, but not the only example of this type of legislation. Other conservation legislation, such as the Sea Turtle Act (Public Law 101-162) and the Marine Mammal Protection Act of 1972, displayed a similar focus.

The emergence of conservation biology reflected a shift in emphasis and a break with historic perceptions about the nature of the “endangered species problem.” The traditional view of recent extinctions as a collection of tragic, individual case histories was replaced with a conviction that the global extinction crisis was caused by fundamental disruptions of ecosystem processes. Extinctions came to be perceived not as a sad parade of passing species, but as losses in genetics, community attributes, and ecosystem properties. With changes in perceptions of what was being lost came changes in perceptions of why species were being lost. New studies shifted emphasis from natural history to identifying the ecological processes that contributed to emerging patterns of extinction. The extinction crisis created an urgency to develop an alternative concept to that of “endangered species.” That concept was biodiversity.