Since 1500, more than 320 terrestrial vertebrates have become extinct.
And scientists believe this is an indicator that we are reaching our 6th mass extinction tipping point. Did you realize that there were 5 before this time? If not then do a little research, specifically take a look at what the Myans research indicated. You will be amazed and perhaps a little frightened.
By the way, those animals we mentioned, the populations of the remaining species show a 25 percent average decline in abundance. Many believe the situation is dire for invertebrate animal life.
Previous extinctions have included floods, fires, asteroid strikes and other catastrophic events.
How will losing animals cause the next extinction? The lost species represent a relatively low percentage of the animals at risk but their loss would have trickle-down effects that could shake the stability of other species and, in some cases, even human health.
Example: If the large animals become extinct then the smaller animals can and will take their place. For instance; areas will become overwhelmed with rodents. Grass and shrubs increase and the rate of soil compaction decreases. Seeds and shelter become more easily available, and the risk of predation drops.
Consequently, the number of rodents doubles — and so does the abundance of the disease-carrying ectoparasites that they harbor.
“Where human density is high, you get high rates of defaunation, high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission,” said Dirzo, who is also a senior fellow at the Stanford Woods Institute for the Environment. “Who would have thought that just defaunation would have all these dramatic consequences? But it can be a vicious circle.”
“We tend to think about extinction as loss of a species from the face of Earth, and that’s very important, but there’s a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well,” Dirzo said. “Ironically, we have long considered that defaunation is a cryptic phenomenon, but I think we will end up with a situation that is non-cryptic because of the increasingly obvious consequences to the planet and to human wellbeing.”[SOURCE](http://www.sciencedaily.com/releases/2014/07/140724171956.htm)