In nature, animal populations are limited by a number of constraints, such as the supply of food and water and space (territory). Additionally, other balances are put in place in the form of disease and predators. These factors keep animal populations in check and prevent them from overpopulating and experiencing a distributed suffering.
Humans were once governed by these same principles, but since the introduction of the first technologies (fire and tools), things have been changing. Humans have steadily marginalized the threats posed by predators by creating weapons and destroying populations of dangerous animals. Disease, an arguably more effective population control, has also been marginalized through the advancement of medicine. The development of water purification, farming techniques, and the utilization of vertical space have allowed humans to overcome the other constraints as well.
Now, because of mankind overcoming the limitations of the natural constraints placed on population growth, the human population on the Earth is exploding. A single country, China, now has about one-and-a-half billion people. As the population expands, there seems to be no sign of it stopping either. The population of the Earth is expected to extend into the tens of billions in the 21st century.
Clearly, there is a limit to human expansion. There is a limited amount of clean water, limited amount of land to catch solar energy and grow food, and a limited amount of space. However, if we allow the human population to grow unchecked until we reach the limits of our resources, the human race as a whole will suffer greatly. Since nature isn't really regulating our population anymore, who or what is?
Many modern problems can be traced back to overpopulation as a cause. Drinking water shortages, environmental destruction, starvation, poverty, disease, overfishing, and the increasing scarcity of natural resources such as oil are all problems that are directly caused by or worsened by overpopulation. One of the greatest threats facing mankind is the finite oil supply, since we have overextended ourselves to the point where we need oil to fuel our agriculture. Since oil is a limited resource and will run out at some point, we need to develop alternative energy or watch our agricultural production collapse when we run out of oil.
How large will we allow the human population to grow before we draw the line? Already, the Earth's resources are being strained due to things like overfishing, pollution, and non-sustainable growth of cities. Already, hundreds of millions of people suffer in poverty because their country does not have enough resources to support all the people inside. Strangely, the most populated countries in the world also have some of the lowest per capita income. Additionally, one could argue that systems of charity that give resources to overpopulated nations with hardly any resources are only encouraging further population growth, resulting in more suffering.
China has finally started to limit its ridiculous growth rate by limiting the number of children families can have. This has had some success in stabilizing their population, but other countries have failed to adopt similar initiatives. Now we have to ask ourselves, do we want to have a decent population size on Earth that can live comfortably or do we want an utterly massive population that the Earth can barely support and suffers as a result?
Placing limits on population growth is obviously a touchy subject. After all, who wants their government telling them how many children they can have? However, as human longevity increases along with the population, there has to be some point where governments step up and decide to do something about it. Obviously it would be highly unethical to massacre people to decrease the world population, but governments can still verbally discourage their population from growing or take steps like China to stem birth rates.
Population control is a touchy subject, but it is not something we can just ignore anymore. In the coming century or two, difficult choices will have to be made about the future of the planet and how to deal with uncontrolled population growth. If we want to defy the balance of nature, we have to take responsibility for ourselves and ensure that we are not making mistakes that will result in widespread suffering.