A windbreak, as we generally think of it in Iowa, is a narrow belt of trees planted to give the farmstead protection against winter winds. Much of Iowa’s land is relatively level to gently rolling. There is little native timber except along rivers and streams. This combination permits northwesterly winter winds to make a clean sweep across the land. Something is needed to break their force.
Campbell, R. B. and Grau, R. B.
"Evergreen windbreaks for Iowa farmsteads,"
Bulletin P: Vol. 4
, Article 1.
Available at: http://lib.dr.iastate.edu/bulletinp/vol4/iss88/1