Conserve Wildlife? How?

I was not able to find anything that said why we don't just build buildings up instead of outward, but I had to give a guess I would say that it is probably easier and cheaper to build a building that stretches outward instead of upward.  I did however find some ways that we can help conserve our wildlife this site

Some things that I found out were, one, just how fast wildlife is being destroyed especially over in Africa for example one statistic was that there were 5-10 million elephants in the African plains back in the 1930's and and then by 1989 which is when they were added to the most endangered species list there were only about 600,000 of them left. Statistic from this site.  

For my next post I would like to keep looking for exact reasons why we don't build up instead of out  also more ways for us to help conserve our environment and finally we don't educate more people on this topic.