Natural elements of the ecosystem are often borderlands, for example rivers or mountains, the Great Lakes.
He wanted to restrict the supply in order to raise its price. Farmers were growing too much of their crops and as result demand started to go down.
Relatives to people who are already here is the answer in this question. People who are already in the country and earn much money to make their family lives immigrate to that country because their life will be stable. So the relative of the person who are already in that country is the reason why there has a large number of immigrants.
