In environmental science, what does "biodiversity" refer to?

Biodiversity refers to the variety of life in a particular habitat or ecosystem. It encompasses the range of different species, their genetic variations, and the ecosystems they form. This diversity is essential for maintaining the balance of ecosystems, as each species plays a unique role in the environment, contributing to processes such as pollination, nutrient cycling, and food webs. High biodiversity typically indicates a healthy and resilient ecosystem capable of withstanding environmental changes.

While the other options may relate to aspects of environmental science, they do not accurately describe the concept of biodiversity. For instance, counting humans in a region focuses on a specific population rather than the variety of life forms present. Similarly, examining genetic similarity among species is a narrower focus that does not capture the full scope of biodiversity, and discussing the quantity of natural resources available pertains to resource management rather than the variety of life itself. Thus, the correct definition of biodiversity is indeed centered on the variety of life within a specific ecosystem or habitat.