People and people and people!
There is a concept in wildlife biology called carrying capacity. This means that any stretch of wildlife habitat can support only a certain number of particular types of wildlife. Take for instance the tiger. A normal full grown tiger needs about 20 square kilometers of space. Thus s particular wildlife sanctuary can only support a finite number of tigers. Once it exceeds it carrying capacity, the tigers tend to leave the sanctuary to enter areas surrounding it with often fatal consequences as recently seen in Ranthambhore where local villagers poisoned two sub adult tigers which had entered their areas from the now crowded National Park. Unfortunately nobody thinks of extending this analogy to humans. The world population has increased to 6.8 billion and shows no sign that it will level off anytime soon. There is some hope that the world population levels will level off at 9.2 billion according to some estimates, other estimates are far more pessimistic. Occasionally we see idiot re...