Yes, biodiversity is changing now. Unfortunately, human activity is causing plants and animals to go extinct at rapid rates, and causing the ranges of other species to be drastically reduced. By some estimates, the rate of extinction is now 100 times greater than the natural rate because of humans, and our modern period is often called “The Sixth Mass Extinction” with reference to biodiversity loss. (Read more about mass extinctions here)
This figure is called the Living Planet Index; it was compiled by the World Wildlife Fund in 2005, and is based on data for several groups of marine, freshwater, and terrestrial animal species. As you can see, abundance of all has declined since 1970 levels.