Overpopulation. Some jumbled thoughts

A recent report suggests that the population of the world is due to rise to near 11 billion people by 2100 it is currently standing at just over 7 billion. the greatest growth will be found in Africa and South East Asia.
Nature controls populations with predators but to date none, excluding other humans, has been seen among the human race since the bubonic plague decimated communities in the 14th century.
The increased population will mean more food production, less natural habitat for other animal species. many, now, are already close to extinction and will surely go. There must come a point when the globe is full; there is no where else for mankind to go to except space. But is this the legacy of mankind; to lay waste planet after planet, killing the indigenous species? Have we become the very aliens we always feared, travelling through space destroying every planet we colonise.

However, is it possible that nature will redress the balance. If man doesn't take steps to curb their growth nature will do it, either with natural physical effects such as climate change, supervolcanoes, asteroid bombardment or epidemics. But how and why does nature take a hand in this?
Is it because the universe is a composite of two parts, the part we exist in and another, described by Kant as 'transcendental'. This means that planet earth has a counterpart which exists in a symbiotic relationship, ensuring that there is always a balance to maintain an unknown evolutionary advancement. There is no point to this evolution; it just goes on with the natural eradication of life a possibility. Achieving this balance includes the remedies offered above but one mustn't discount the possibility of mankind being responsible for remedy through wars and scientific advancement such as AI.

All the while, science, medicine, works hard to reduce deaths and prolong lifetimes obeying the mantra that 'life is sacred'. Has 'civilised' man got it wrong? Should all life be sacred or just some? Take murderers for example. Should a paedophile who murders his young, innocent victims be maintained at great expense for his life? What about a killer of public servants in the course of their duties? If people need to be culled why not start with these? 
When the world cannot support everyone, who next shall be sacrificed? Those who behave unsociably by killing, thieving, or otherwise cheating? But wait a minute; perhaps this is contrary to nature! Nature has cheats in the animal kingdom; they play a part in the grand picture so do they serve a purpose. Pol Pot had a vision whereby he emptied the cities of Cambodia and slaughtered all the intelligentsia, totally at odds with conventional behaviour.