We can't build a fence; wouldn't be prudent. It'd endanger wildlife, according to a group of U.S. government scientists that claim fencing along the Mexican border threatens the black bear population.
Of course, our taxpayer-funded "scientists" have no interest in reporting facts that run counter to their bias:
Buenos Aires National Wildlife Refuge, Sasabe, Pima County, Arizona -
Trash — During 2009, an estimated 51-82 tons of litter were left on the Refuge by approximately 20,700 illegal immigrants. Based on Refuge monitoring efforts, each border crosser deposits an average of about 5 to 8 pounds of trash on the Refuge. Trash has significant impacts to wildlife, habitat and public safety, not to mention the loss of aesthetic values.
Wildfire — Several fires are started each year by illegal immigrants resulting in significant environmental damage and cost to the government. Two fires in the vicinity of the Refuge in 2009 burned over 23,000 acres and cost federal and state governments $1.2 million to suppress. Wildfires put both other illegal immigrants and the visiting public at risk as well as potentially impacting critical habitat and listed species.
Livestock Trespass — Illegal immigrants often damage or cut fences or leave gates open, allowing cattle to enter the Refuge. This directly impacts Refuge wildlife habitats and exposes neighboring ranches to disease transmission from untreated Mexican livestock.
These taxpayer-funded "scientists" don't want to talk about things like that, as it conflicts with their agenda. These folks aren't scientists, and taxpayers shouldn't be funding them; they seek to further their ideological agenda under the pretense of science, while feeding heartily from the taxpayer-filled trough.