Biodiversity in flux

OK so what makes for low biodiversity?

EXTINCTIONS

what causes extinctions?

in order
1. habitat destruction
2. habitat fragmentation
3. invasive exotic species
5. over exploitation

Look at extinction rates like a river. The river is fed primarily by ground water, and it generally has a certain stage that it doesn't fall below even if it hasn't rained in a long time. This is called baseflow. Paleo-ecologists have discovered that over the course of life on earth, there is a constant "baseflow" of extinctions. A steady rate that can be considered natural as the world changes. Now there are other events that cause the discharge of the river to increase such as a rainstorm or spring melting in our analogy that temporarily increase the flow, and give it all its variation. These events could be the ebb and flow in the extinction rate over time. But over life's history there have been five floods. in other words mass extinctions.

In nature, floods are inevitable. They are statistically destined to return to any given stream. Just as mass extinctions are destined to return at certain intervals to Earth. But the interesting thing is that after a mass extinction, biodiversity has the tendency to climb to a higher point than its pre-extinction peak.
(Again don't take my word for it, check out Wilson's Diversity of Life)

The most recent mass extinction was the end of the Dino-days caused by a massive collision with the earth's surface. Boy, they must have been surprised! Well, its always possible that another such event will occur and wipe out tons of species. And maybe we'll call that Big Mama of an asteroid Homo sapiens sapiens. If we're still around to call it anything!

In all seriousness we are in the sixth mass extinction. (David Quammen planet of weeds) weep about it if you want. Did you notice that those four things above all seem pretty human caused? Yep. Its our fault. We don't really know what this means for humanity yet, or for Earth. what have we ever realy known? But realistically life is still worth living, right?! Guys?

guys?