http://www.windmeasurementinternational.com/wind-info/wind-energy_faq.php
How much space do wind turbines need?
A standard wind farm of 20 turbines will extend over an area of about 1 square kilometre, but only 1% of the land is used for the turbines, electrical infrastructure and access roads. The rest of the land can be used for farming or natural habitat.

That's about a 9th of an acre per tower. One can hope for millions of acres to be uses, we've got more than 3 billion of them