英語聽力：猛瑪象進(jìn)城記—11

At first, the Europeans relied heavily on local food supply by native people. But as they settled in, their farming practices began to shape the landscape of North America.

The plow allowed them to farm larger areas of land, helping to feed the expanding population.

While this new type of agriculture robbed many animals of their habitat, others were to reap the benefits.

Birds such as grackles, cowbirds and red-winged blackbirds exploded in numbers, feeding off the waste remains of farming. These pest birds were already common around small native farms in the east. Now large scale farming of crops such as corn, wheat and barley fuel(s) their numbers to epidemic proportions.

Despite these pests, North America's agricultural kept on booming, becoming big business. Great sways of a once wild landscape have been turned over to farming.