If you know how the world's ecosystem works, you will understand 'balance in nature' better. Let me explain. An ecosystem is basically an entire self-sufficient biological system. It consists of all sorts of living things that feed off each other i.e. Plant absorbs sunlight, deer eats plant, tiger eats deer, etc. And the cycle continues. This was a very simple example, though an ecosystem is more complex and made up of many different types of living things, but you get the gist. An ecosystem basically needs no help from the outside of its boundary to continuously sustain itself. A 'balance in nature' therefore, is the continuous balance between all these living things as well as environmental factors. For example, if the only carnivore (meat-eater) in a specific ecosystem is the tiger, and for some reason it is going extinct (maybe man has killed most of them for their fur), then that means the deer will be allowed to flourish and plants will also start to diminish. This is how an imbalance in nature could come about. Another example could be global warming (maybe caused by air pollution from our vehicles), which would cause the ice caps in the mountains to melt, hence causing flooded rivers, which in turn would kill much plant and animal life, and again cause an imbalance in nature. The disruption of the balance of nature can caused by a number of things, but more often than not, it is attributed to something us humans are involved in. Either we're cutting down too many trees and causing deforestation, or we're hunting too many animals of a specific species for sport or trade, etc. We must be careful and respect nature and the precious balance it tries to maintain. Sometimes nature comes back to bite us, through tsunamis, hurricanes, flash floods, etc. We end up asking God why he let that happen, when it was US who ultimately had upset the 'balance of nature'.
