Why is it important that alien grass, trees, and other plants choked out native vegetation?

Me! these questions are based on american people in the south essential questions: question 1: for what reasons will one group of people exploit another? focus questions: question 1: what influenced the development of the south more: geography, economy, or slavery? question 2: what were the economic, political and social arguments for and againsts slavery in the first half of the 19th century.