Barack Obama declared the largest single land monument of his presidency on Friday – the same week that federal officials aggressively targeted rightwing activists who have rebelled against what they characterize as “land grabs”.

Obama nearly doubled the amount of public land he has protected as national monuments with a move to conserve nearly 1.8m acres (0.7m hectares) of the California desert. The executive action came one day after federal authorities arrested and charged the unofficial leader of the anti-government movement in the west and successfully ended a militia standoff in Oregon inspired by these kinds of national conservation policies.

With the unraveling of the anti-government protests and Obama’s large-scale land preservation efforts in California, it has been something of a watershed week in the fight to protect public wilderness against attacks from conservative activists, experts noted.

Cliven Bundy, the Nevada rancher who led a 2014 standoff with the government over his refusal to pay grazing fees, was taken into custody in Portland on Wednesday night and charged with six federal crimes. He had been on his way to the armed occupation led by his sons of a federally protected wildlife refuge in eastern Oregon. The final four occupiers surrendered on Thursday, and a total of 25 people are facing charges in a federal conspiracy case.

Even with the aggressive prosecutions, conservative critics may still be fired up to organize against Obama’s latest land initiative.

“The anti-government movement is going to see these designations as the actions of a tyrannical force,” said Ryan Lenz, a senior writer with the Southern Poverty Law Center (SPLC), a nonprofit that has closely tracked rightwing groups and militia efforts inspired by the Bundys. “They’re going to see this as further proof that these lands are being taken from American citizens. How this manifests is the question.”

Obama, who has protected more land and water than any of his predecessors, designated three new national monuments in southern California on Friday, called the Mojave Trails, Sand to Snow and Castle Mountains.

Mojave Trails – a 1.6m-acre area with mountain ranges, lava flows and sand dunes, and habitat for threatened desert tortoises – is the largest single land monument the president has declared. Combined with adjacent protected sites, Obama’s declaration has created the second-largest desert preserve in the world.

The Sand to Snow monument hosts more than 240 species of birds, and the Castle Mountains monument is a wildlife corridor for golden eagles, mountain lions and bobcats and is home to Native American archeological sites.

The California terrain and politics are different than the conditions in Oregon, where the Bundy militia standoff seized on ranchers’ grievances against the federal government for restricting cattle grazing on public lands to protect rare and endangered species.

But the absence of a frustrated rancher community and high-profile dispute in California may not matter much to anti-government activist groups, which have grown dramatically since Obama entered the White House.

Anti-government militias jumped from 42 groups in 2008 to a peak of 334 groups in 2011, the SPLC reported. “When [Obama] was elected in 2008, almost immediately the anti-government movement boomed,” Lenz said.

Cliven Bundy’s fight significantly energized these ultra-conservative activists – with the number of groups climbing by more than one-third in the last year, according to SPLC – and they have increasingly organized in opposition to federal public land restrictions.

“The movement has been looking for … a fertile battleground to go to war with the federal government, and I think they found it in the issue of land use,” Lenz said.

Obama – whose administration has “big, big ambitions” for more conservation designations this year – has often been a direct target of land-use rights’ protesters.

In a significant push to solidify his lands legacy, the president last year created three new national monuments in Nevada, California and Texas, sparking opposition from local officials and ranchers.

But with three Bundys in jail, it remains to be seen if and how activists may seize on mass conservation efforts like the new California designation. “In the absence of the Bundys, who have taken this ire farther than anything before, who is going to step up?” Lenz said.

Environmental groups backing the desert monuments said they were hopeful Obama’s latest move would not inspire any substantial dissent or rightwing activism.

“The people that live and work in the desert are supportive of this,” said Ileene Anderson, senior scientist with the Center for Biological Diversity. “They see public lands as a benefit … and they want to have these places preserved.”

But, Anderson added, “I don’t know how it would galvanize people outside of the desert.”

