From The National Geographic:
As of 1995 only 17 percent of Earth’s land remained free of direct human influence, as seen in this map of the vast networks of shipping lanes and roads that crisscross the planet.
“On average, the net benefits to humankind of domesticated nature have been positive,” the authors write in tomorrow’s issue of the journal Science. For instance, leaps and bounds in agriculture have increased food supplies and made for easy access to energy-rich, easily stored grains.
More here.