In the light of evolution II: Biodiversity and extinction

The Earth's biodiversity is a wellspring for scientific curiosity about nature's workings. It is also a source of joy Andy inspiration for inquisitive minds, from poets to philosophers, and provides life-support services. According to Kellert (2), biodiversity affords humanity nine principal types of benefit: utilitarian (direct economic value of nature's goods and services), scientific (biological insights), aesthetic (inspiration from nature's beauty), humanistic (feelings deeply rooted in our inherent attachment to other species), dominionistic (physical and mental well-being promoted by some kinds of interactions with nature), moralistic (including spiritual uplifting), naturalistic (curiosity-driven satisfaction from the living world), symbolic (nature-stimulated imagination, communication, and thought), and even negativistic (fears and anxieties about nature, which can actually enrich people's life experience). Whether or not this list properly characterizes nature's benefits, the fact is that a world diminished in biodiversity would be greatly impoverished.Many scientists have argued that, as a consequence of human activities, the Earth has entered the sixth mass extinction episode (and the only such event precipitated by a biotic agent) in its 4-billion-year history (3, 4). The last catastrophic extinction, which occurred ≈65 million years ago and was the coup-de-grace for non-avian dinosaurs, marine ammonites, and many other evolutionary lineages, happened rather suddenly after a large asteroid slammed into the planet. Today, most of the biotic holocaust is due—directly or indirectly—to local, regional, and global environmental impacts from a burgeoning human population. The first phase of the current extinction episode started ≈50,000–100,000 years ago, when modern humans began dispersing around the planet. The second phase started 10,000 years ago with further population increases and land-use changes associated with the invention of agriculture. A third phase of environmental alteration and bio diversity loss was ushered in by the industrial revolution. E. O. Wilson (5) estimated that the Earth is currently losing … [↵][1]†To whom correspondence may be addressed. E-mail: javise{at}uci.edu or fjayala{at}uci.edu [1]: #xref-corresp-1-1