Nature has funny ways of doing things. Rhinos, elephants and lions have no natural predators, but as the great flowchart in the link shows, this doesn't matter. Both the survival and demise of the species are consequences of human actions.
While around 18,000 new animal, insect or plant species are discovered yearly, other species are on the edge of extinction — including some that are newly discovered and others that have been around in some form for million of years.
The African continent alone has more than four large mammals whose populations are, for the most part, declining at a worrisome pace. They include the gorilla, elephant, lion and rhino. The latter three are particularly in danger due to illegal poaching, with byproducts typically being exported for medicinal or other consumer use — part of a multi-billion dollar industry.
There are many laws and international conventions that regulate poaching and the trade of illegally sourced products, but governments across the world and international agencies have to step up on the task of enforcing these treaties.
If we do it sooner, rather than later, we will be able to witness and research animals in there natural habitat for many generations to come.
Check out the flowchart yourself: