IN A RURAL TOWN IN East Texas, a battle is being waged between a multinational energy corporation and an alliance of rural landowners and environmental activists.

A gravel road leads to the battleground. Towering oaks punctuate the gray October sky and the damp ground is overgrown with moss. It’s a fairy tale-like scene, marred by yellow police tape and the grating of heavy machinery slicing through trees and heaving up soil.

This forest near Winnsboro is the unlikely epicenter of a growing movement to halt the Keystone XL pipeline, slated to bring oil stripped from the tar sands of Canada to the Texas Gulf Coast. In an effort to stop the steady progress of the pipeline, protesters have taken to the trees—living on wooden platforms 80 feet in the air. Their platforms dot the tree canopy within an easement obtained by TransCanada, the corporation building the pipeline.

The tree-sitters have been living in this tree village, which they’ve dubbed “Middle Earth,” for a month. Their world is confined to the 4-by-6-foot platforms and the ropes connecting them. They’re able to zipline between platforms, but the structures only offer enough room to sit or lay. If they want to stretch their legs, they use a catwalk—nicknamed “Helm’s Deep”—that extends 100 feet across the tree village’s northern boundary. Below, a police officer asks anyone who approaches the easement for identification and waits to arrest any protesters who might come down.

In this increasingly tense showdown, the stakes couldn’t be higher. Presidential candidate Mitt Romney promised to build Keystone XL himself if elected to curb U.S. dependence on foreign oil. On the other side of the debate, environmentalists view stopping the pipeline as essential to keeping vast amounts of carbon in the ground and out of the atmosphere. And landowners, farmers and even some tea party types up and down the pipeline route are raising a host of objections, from potential contamination of aquifers to the trampling of private-property rights.