Many people, including residents of border towns, environmental activists, privacy advocates and government watchdog groups, have raised concerns about the fence's impact on the environment, economic activity, tourism and privacy.
Some critics question the technology behind the virtual fence. For example, cows have set it off. A concerned rancher also told the Associated Press that a government official had indicated that the tower's warning horn could go off automatically if anything -- human or animal -- gets too close [Source: St. Louis Tribune].
It's also unclear how much the full virtual fence will cost. Companies competing for border security contracts have said it's a $2 billion contract over six years. But the costs of past border fences, such as the one in development since 1994 along parts of the California-Mexico border, have skyrocketed beyond initial estimates. The cost of the new, complete virtual fence could be as much as $30 billion.
Privacy remains a concern for residents of towns near the virtual fence. Many residents of these communities enjoy their secluded living conditions. Given their extremely long range and proximity to some towns, the tower-mounted cameras could be used to look into private homes and businesses. The government says they won't be used for that purpose, but privacy advocates and local residents are concerned. Besides the cameras, underground sensors, helicopters and Border Patrol vehicles could leave border town residents feeling like they're under constant surveillance.
The territory along the Arizona-Mexico border contains important migratory routes for animals and several national parks. The virtual fence's towers, vehicles and helicopters could disturb animals in the area. Questions have been raised about whether the use of radar will adversely affect bats and honeybees. The physical portions of the fence are set to pass through areas frequented by rare animals such as the ocelot.
But illegal immigration exacts its own toll on the environment. Large amounts of litter and waste are strewn along migrant routes. Truckers and off-road vehicles carve illegal roads through canyons and hillsides, disrupting the natural habitats of local animals.
Beyond privacy and environmental concerns, there's the question of whether the way of life for people living along the U.S.-Mexico border will change. We'll look at this in the next section.