Confusing

In Oregon various groups are attempting to recreate the man-made savannas, created by Native Americans many years ago:

For thousands of years, fires lit by indigenous peoples maintained oak savannas. Such forested grasslands were once abundant across the western US, but agriculture, lumber industry, and fire suppression have combined to bring them close to extinction. In Oregon's Willamette Valley, bringing them back is laborious work that sometimes involves sacrificing stands of other native trees.

The savannas were not the natural ecosystem of the land.