Majestic old-growth trees stand within one of the national monuments that President Donald Trump wants to dramatically shrink in size or do away with.

The Giant Sequoia National Monument, which falls within California's Tulare, Kern and Fresno counties, is one of several sites in the crosshairs. The giant sequoia trees are some of the largest and oldest living things on Earth, towering giants with limbs stretching skyward 300 feet in the air.

But a battle brewing far below the treetops could determine the future of the Giant Sequoia National Monument, CBS San Francisco reports.

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Some are on board with the president's plan, saying it could help reduce fire risk in the area.

"Locking them up in a monument and doing nothing, which is essentially what the Forest Service has done for the past 20-plus years, is not in their best interest," Tulare County Supervisor Steve Worthley said.

The Trump administration is considering a plan to shrink the monument by more than two-thirds, from its current 328,000 acres to roughly 90,000, a plan that's found some unlikely allies.

"I don't think anybody had an intent to destroy or diminish this treasure that we have in our backyards," Tulare County Board of Supervisors Chairman Pete Vander Poel said.

Vander Poel voted against the letter sent on behalf of the Board of Supervisors in support of reducing the size of the monument, a proposal so polarizing that only the three supervisors in favor of it would sign their names to it.

Supporters of shrinking the monument say a lack of management coupled with massive tree die-off after years of drought have left it weakened and vulnerable to wildfire.

They say a smaller monument would be better managed and more protected.

But critics say the plan is not really about preserving or restoring a forest, as much as it is about resurrecting the timber industry.

"Taking any kind of designation from the few pieces of protected land, of intact habitat that we have, is a mistake," environmentalist Mehmet McMillan said.

The giant sequoia groves and the land surrounding them is currently protected from logging, but that could change.

There is little dispute that the estimated 8 million dead and dying trees, just in the monument alone, have increased the threat of wildfire but it's not clear if private companies would have any interest in bark beetle-infested wood, even if logging were to resume.

Critics say the answer is to increase funding, not to decrease the size of the monument.

"By taking any kind of protection away in any way is basically a slap in the face," McMillan said.

On Tuesday, lawmakers on both sides of the aisle sent a letter urging the feds to protect monuments like these.

San Francisco-based Earthjustice, a nonprofit environmental law organization, says that in addition to Giant Sequoia, six other California sites could be in question: the Carrizo Plain Monument, Berryessa Snow Mountain, Sand to Snow, San Gabriel Mountains, Santa Rosa & San Jacinto Mountains, and Mojave Trails.

In Arizona, part of the Grand Canyon is also under review.

The order draws special attention to the latest designation, the 1.3 million-acre Bears Ears National Monument in Utah. Republican Governor Gary Herbert and the Utah legislature have asked the Trump administration to rescind the designation of Bears Ears as a national monument.