LOS ANGELES (CN) — The man walked at an even clip through a creek shaded with elms. Holding a fishing rod, he glanced from beneath his cap as he passed an outcropping of rocks where a woman looked up from her packed lunch and asked if he had caught anything.

No, there’s no fish left in this river, he replied matter of factly, barely stopping to take a breath as he crossed onto a dirt trail. He had no time for small talk. Either that or he was eager to find a better place to cast a line. Somewhere. Not here.

The woman, Dianne Erskine-Hellrigel, watched through her large sunglasses as the man receded into the distance, her bright blonde lanyard pigtails brushing against her shoulders. Fishing season started in mid-May, and at another time the fisherman would not have left empty-handed, she said.

Later, as we walked back along a trail in Cattle Canyon dotted with yuccas, we passed an unkempt, bearded man with unruly dark hair, dressed in a long-sleeve shirt and pants. Not for the first time that day, Erskine-Hellrigel, an avid hiker and environmental activist from Santa Clarita with a warm, throaty laugh, was the first to say hello.

As he walked away, she seemed to recall meeting the man before, farther up the canyon. Back then he had been wearing a long velvet coat and was in the canyon mining for gold. Since he did not look like a hiker, she asked what he was doing and he told her he was mining for gold. He glanced over his shoulder and then produced a gold nugget the size of a golf ball from inside a deep pocket – enough to make a living.

But for Erskine-Hellrigel, with the environmental group San Gabriel Mountains Forever, gold dredging and mining pose a grave threat to the Santa Ana suckers and trout in the river.

“Part of the issue is that they’re making a living pulling gold out of here, but all the ﬁsh are dying. They disturb the banks and the water becomes muddy, and the ﬁsh can’t breathe, and so they go belly up,” she said.

Gold panning and dredging are not the only things affecting the environment at Cattle Canyon, at the East Fork of the San Gabriel River, which is part of a $10 million to $15 million improvement project to clean trash, scrub graffiti and remove invasive species of plants. The canyon is a well-trodden area that is a favorite weekend spot for Angelenos looking to escape the city and swim in the river, bathe in pools, or bungee jump from the “Bridge to Nowhere” at the end of a 5-mile hiking trail.

Diapers, trash, graffiti, manmade dams, trails and invasive species of plants are all making a mark in the East Fork, and it is not a good one. But with the improvement project, the San Gabriel Mountains National Monument is taking advantage of its 346,177-acre designation in the Angeles National Forest to make Cattle Canyon and the East Fork safer and less of an eyesore.

Dressed in a black wide-brimmed hat, gray pants and resting on hiking poles, Erskine-Hellrigel looked down into the gaping canyon from a steep road leading to a parking area. She said the 2.5-mile reach on the East Fork would include picnic areas, a new trail, and roving rangers to educate visitors.

For years, environmentalists dreamed of cleaning up the canyon, reviving fish and native fauna, and doing something to prevent visitors from polluting the water with trash and waste.

Then in October 2014, President Barack Obama declared roughly half of Angeles National Forest and a smaller part of the San Bernardino Forest a national monument. Boosted by its new status, the monument raised millions of dollars for the project, the San Gabriel River Confluence with Cattle Canyon Improvements Project, a partnership between the Watershed Conservation Authority and the Angeles National Forest San Gabriel Mountains National Monument.

Now its future is uncertain.

On April 26, President Donald Trump ordered a review of all national monuments that had been declared under the Antiquities Act in the past 21 years, and created a short list of 27 monuments. Six monuments in California are on the list, including the San Gabriel Mountains National Monument, Berryessa Snow Mountain, Carrizo Plain, Giant Sequoia, Mojave Trails, and Sand to Snow.

The Antiquities Act, enacted under President Theodore Roosevelt in 1906, gives presidents broad powers to protect federal land.

Trump called the national monuments created by his three predecessors, Presidents Bill Clinton, George W. Bush and Obama, “a massive federal land grab” that “should never have happened.” His order calls for a review of monuments more than 100,000 acres in size.

This month Secretary of the Interior Ryan Zinke issued an interim report on the nation’s newest national monument, Bear’s Ears Monument in southeastern Utah, and said he wants to shrink it.

Obama designated the 1.3 million-acre monument in his final days in office. The Trump administration and its supporters sharply criticized Bear’s Ears and other designations as abuses of the Antiquities Act, and the oil and gas industry in the Beehive State has fought for access to natural resources in the monument.

But others are alarmed by Trump’s executive order and say any attempt by the president to delist or curtail monuments would be legally unprecedented and roll back protections for lands, oceans and historic and cultural sites.

Erskine-Hellrigel is confident that the San Gabriel Mountains National Monument falls squarely within the Antiquities Act. San Gabriel Mountains Forever had urged Obama to make the forest a national recreation area. U.S. Rep. Judy Chu, D-Los Angeles, introduced legislation that would have covered the entire Angeles National Forest, but Obama refused to go that far.

“Now they’re reviewing the monument it’s a good thing, because it would have looked like a land grab,” Erskine-Hellrigel said on the drive up Highway 210 to Cattle Canyon, about 40 miles east of Los Angeles. “We’re pretty happy and when it comes to all the monuments. I don’t think ours is on top of being tossed out.”

Cliff Hamlow, of the San Gabriel Valley Legislative Coalition of Chambers, representing business interests, also was confident. He pointed to the harmony between stakeholders and members of the San Gabriel Mountains Monument Collaborative.

“I think probably it’s low on the totem pole,” Hamlow said in a telephone interview.

The monument was already on federal land that is part of the National Forest, Hamlow said. It does not have the natural resources that have spurred protests over access from the oil and gas industry.

“There are only two or three ways into it, and I can’t see that business is going to move up the canyon at all. I don’t see it as being a place of business interests. I think it will be a place of natural resource interest and getting young people out of the inner city into a nature setting,” Hamlow said.

David Czamanske of the Sierra Club in Pasadena told the San Gabriel Valley Tribune he did not think there was much threat to the monument, but encouraged the public to comment to ensure it is not delisted or scaled back. The public can send a form letter supporting the monuments or write their own letter at monumentsforall.org.

“In the San Gabriel Mountains, we have no oil and gas, no timber, no commercial interests,” Czamanske said.

Daniel Rossman of The Wilderness Society was more circumspect. He said he was nervous, partly because of the uncertainty surrounding the review process.

“I can’t see a rational argument for removing these protections, but the other part of my mind is on the short list, and there’s no real clear motivation for undoing any of these protections. It’s truly an unprecedented move to call for this kind of review,” Rossman said in a phone interview.

Rossman said the designation would help ensure that mining and dredging remain prohibited in the monument. California officials are considering a plan for a tunnel under part of the San Gabriel Mountains for a bullet train between Los Angeles and San Francisco.

“If it was shown to have significant consequences to the plants and animals, which seems like drilling a tunnel might, then the monument would offer protection and a way for the forest to stop that project,” Rossman said.

In a letter to U.S. Rep. Nanette Barragán, D-Hermosa Beach, the five members of Los Angeles County Board of Supervisors also voiced their concern, and support for legislation that would protect Obama’s designation.

“President Trump’s executive order could wipe away the over 10 years of work that has been done to establish the San Gabriel Mountains National Monument, including the previous and ongoing community engagement to ensure that stakeholders are all involved,” the May 4 letter states.

Erskine-Hellrigel knows the stakes are high.

“The money that we’re getting is because it’s a monument. And so I don’t know if that money would be withdrawn or if more monies that we have promised to us wouldn’t come, and so that would definitely affect it. And the great thing is the monument gives more protection to the endangered species to the endangered plants, to the precious areas, to the historical sites and the heritage sites,” Erskine-Hellrigel said.

More than 15 million Angelenos live within a 90-minute drive of the San Gabriel Mountains and roughly 3.5 million people visit annually. It accounts for 70 percent of open space in a county that is short on large recreational spaces for minorities and children. About 35 percent of the county’s drinking water comes from the mountains.

Tribal burial sites and endangered species including the California condor, Nelson’s bighorn sheep, mountain yellow-legged frogs and Santa Ana suckers, and historical features including the Mount Wilson Space Telescope need federal protection, Erskine-Hellrigel said.

She has faced more than her fair share of challenges. She taught troubled children from homes torn apart by domestic violence or addiction. In 2003 she scaled the summit of Mt. Everest and during an ice storm had to dig an ice cave with a German climber and stick it out for three days until the storm passed.

Having overcome a near-death experience, it is no surprise that Erskine-Hellrigel, a Republican who says she primarily voted for Trump because she could not stomach Hillary Clinton, remains sanguine.

“I don’t like that he’s just trying to undo some of these monuments. I truly think I understand why he listed all of them and I think it’s because he needed to have some proof that Bear’s Ears and Sand to Snow and a couple of the other large ones were not what they should be. And I truly think that underneath it all, he’s not even going to come here and look at this,” Erskine-Hellrigel said.

Other advocates have been “pretty vicious” about defending the monuments, she said. In contrast, her group invited Zinke and he can expect a warm welcome if he takes them up on it.

“I want signs that say, ‘Welcome Secretary Zinke.’ We want to show you the best of the best in L.A. It can only be in our favor to do it that way,” Erskine-Hellrigel said.

In Rossman’s office is a picture of his son Jonathan, taken when he was 18 months old during a hike in the San Gabriel Mountains. Next to it is another picture of President Obama signing the proclamation establishing the San Gabriel Mountains as a national monument. Rossman is standing on the stage behind the president.

“It’s been incredibly important to preserve this place not only for all future generations, but it’s very personal for me because this is a place where I like to hike and explore with my young family,” Rossman said. “We’re really seeing an incredible groundswell of support for preserving the status of San Gabriel Mountains and if I have any confidence at all, it comes from seeing the incredible support that the community’s showing.”

The Department of Interior is accepting public comment on the national monuments through July 10. Zinke is expected to complete the review of all the monuments in late August.

Courthouse News has been providing in-depth features on some of the national monuments targeted for closure or reduction by the Trump administration, including the Grand Staircase Monument in Utah, The Ironwood Forest in Arizona and Cascade-Siskiyou National Monument in Oregon and California.