What external factors can affect the rate of speciation and extinction?

A changing environment can cause increased rates in speciation and extinction. For example, a changing climate, such as a change from a warmer Earth to a colder Earth that would have happened in the Ice Age, could result in mass extinction of certain groups of species that are not able to adapt to colder temperatures. Other phyla that can adapt will flourish and fill the niches presented by the new conditions. For example, climate change is presumed to have been a factor that resulted in the extinction of the dinosaurs and the rise of the mammals.  

A- a reduction in biodiversity