MPR: Species extinction rate speeding up
New plant and animal species are emerging, University of Minnesota ecology professor David Tilman says, but not nearly fast enough to make up for the toll caused by human activity.

“That’s sort of a 1 million to 4 million year process, and yet we are causing species to be lost at rates of 100 to 1000 times faster,” he says.

And

Scientists estimate there are 10 to 30 million plant and animal species on the planet, most of them unidentified. Each year as many as 50,000 species disappear. Most die off, Tilman says, because of human activity. “We take natural habitats convert them to agriculture, to suburbia, to roads, to monoculture forestry. We fish the oceans so heavily we literally have these trolling nets that scrape the bottom of the ocean clean,” he says.

The article is already a few years old, but makes the point well.
Also see this from Wikipedia.