I thought and thought about the tragedy of the Wall. Walls don't have a good connotation due to historical events- the Berlin Wall, the Great Wall of China (watch Mulan, the Huns were not happy. In real life: the Xiongnu.), the wall of Jericho... I think walls just remind people of what they cannot do, and creates tension and hate.
I understand that it is unfair for immigrants to pass freely, but I understand that refugees need to escape to safety, and are often too desperate or poor to escape lawfully. I also see another problem- wildlife fragmentation.
Animal populations can be separated by physical barriers, and this kind of separation can induce extinction. What happens, say, if the already endangered jaguar population is split into two parts by a wall they cannot cross, in which males are on one side, and females in the other? How can they possibly reproduce. The same can happen with genetics. What if all the muscular jaguars get stuck in Mexico? American jaguars would then experience speciation at Darwinian levels! The muscle mass could decrease over time, and eventually, we'll be left with more cheetah than jaguar-looking jaguars- not ideal for a jaguar's niche. Such jaguars might not even be able to survive!
My proposal is that yes- we can use a "wall," but the wall does not have to always be a physical barrier. Sure, in border cities, it might help security to have a structure, but as for rural areas, I believe there should be a different kind of wall. "Wildland."
The Wildland would surround areas by the border. People would not be permitted to use it, or cross- from the American or Mexican side. It's only fair. The area is for CONSERVATION. The buffer zone should exist on BOTH sides of the border, meaning that border security would be moved up a bit. You'd have to cross that security before getting to the security further down, by the actual border. Rangers can thus provide the first level of security. If any PERSON is found inside, they should be tried in court, according to the side they are on. Probably with fees as the punishment, or perhaps labor. Maybe, some kind of program can be implemented into this wilderness area, in which immigrants can work there, and raise money to become full fledged citizens.
Help this idea gain some ground. I intend to send the President a letter, but support is always nice. The media is a powerful thing.
Specifications on the size of the buffer zone and how it would react with rural private owned property, is not fully developed. Yet, conservation efforts will help both countries improve things like water availability, soil quality, and more that we already see as separate issues.