A WORLD OF GARDENS 
109 
and in time the prairie disappears to be replaced 
by a forest. 
When trees and prairies are allowed to grow 
by themselves, they still follow this succession. 
The thousands of new settlers coming to Amer¬ 
ica, however, changed all this. First of all, 
they needed homes and fire; so they chopped 
down trees to build log cabins. Later they 
built board houses. They burned wood to heat 
their homes and to cook their food. The next 
thing they needed was food; so they plowed 
up the prairies for farms. Often times a forest 
would interfere with a man’s farm, and he 
would kill the trees to get them out of the way. 
At first no one realized what a serious mis¬ 
take these people were making. Only about 
fifty years ago, the citizens began to wake up. 
They discovered that their fine forests were dis¬ 
appearing. The forests in the eastern United 
States are about gone. Wood has become very 
expensive, although we need it more than ever. 
Trees cannot be replaced in a year like corn or 
wheat. It takes fifty to a hundred years, at 
