Life is growth. Life is consumption. Life is waste. This is inescapable. Clearly more life, means more consumption.
More people means more consumption and waste.
You might argue that two careful people could consume less than one average person which is true, but statistics don't bear this out. Thus, on average two people consume more than one. 4. It is not known, but I believe is is in the tens of thousands from what I have heard about the destruction of the rain forests. But the rain forest is only one of many environments destroyed. People require space which takes away space for other species.