What would Trump's expanded border wall mean for the Southwest?

A U.S. flag put up by activists who oppose illegal immigration flies near the US-Mexico border fence in an area where they search for border crossers October 8, 2006 near Campo, California. The activists want the fence expanded into a fully-lit double-fenced barrier between the US (R) and Mexico. US Fish and Wildlife Service wardens and environmentalists warn that a proposed plan by US lawmakers to construct 700 miles of double fencing along the 2,000-mile US-Mexico border, in an attempt to wall-out illegal immigrants, would also harm rare wildlife. Wildlife experts say cactus-pollinating insects would fly around fence lights, birds that migrate by starlight in the desert wilderness would be confused, and large mammals such as jaguars, Mexican wolves, Sonoran pronghorn antelope, and desert bighorn sheep would be blocked from migrating across the international border, from California to Texas.

Presidential candidate Donald Trump is calling for an expanded wall along the US-Mexico border – but local communities have been through this before.

Republican presidential candidate Donald Trump is calling for an expanded wall along the US-Mexico border as part of his immigration plan, released this week on his campaign's website.

It's not a new idea – and a perennial talking point every election season – but it seems to be gaining traction. According to the most recent CNN poll, one-quarter of registered Republicans now support Trump for president.

"Communities along the border have been through this before," said Melissa Del Bosque, reporter with the Texas Observer who writes the La Línea blog. "Most of the land on the border in Texas is privately-owned so a lot of land owners have been sued by the government and have had their land seized."