Much of this border zone is remote and inhospitable - generally too rough to hike through unless you're a black bear or a pronghorn sheep, species that have flourished in the area's deserts and mountains.
And that's the way Mexico wants to keep it.
While the proposed Rio Bravo del Norte Natural Monument is only about nine metres wide, it will connect two large protected areas south of the river. When a third nature reserve, known as Ocampo, is created this year, the protected areas in Mexico will form a "wall" of millions of hectares of wilderness, matching Texas' Big Bend parks metre-by-metre along the border.
"This stretch of border is the safest one we have. It's safe because it has wilderness on both sides," said Carlos Manterrola, who heads the environmental group Unidos Para la Conservacion.
Big Bend National Park has had some problems with migrant and drug trafficking, but superintendent John King says extending protected areas on either side of the border will likely keep the problem from getting worse.
"When you have a roadless area, you make it more difficult for these activities to happen," King said.Full article