California's border with Baja California is a complex region with unique environmental issues. Our Borderlands series takes a deeper look at this region unified by shared landscapes and friendship, and divided by international politics.
It's more and more likely that Donald Trump will become the Republican Party’s nominee in the Presidential election. As a result, it’s time to start taking a serious look at his signature policy proposal — clamping down on immigration, primarily through building a massive wall along the U.S. border with Mexico.
That’s not a straightforward task, primarily because Trump hasn’t exactly been generous with the details of his signature border wall proposal. So far the wall has been vaporware, long on promises that it’ll solve more problems than it creates, and short on any actual specs. When that’s been mentioned to Trump, he’s tended to comb over the bald lack of detail on the wall with a rhetorical wave of the hand.
Still, the wall is a keystone of Trump’s campaign, and so it makes sense to examine the effect the wall would have on the borderlands’ environment. And it doesn’t look good, even without the wall’s chief proponent offering much in the way of any actual details. We’ve come up with three reasons why, and will be describing them in stories this week. First up: the wall’s effect on the climate.
Here’s one of the very few facts we know for sure about Trump’s Wall: The United States’ border with Mexico is 1,954 miles long, stretching from San Diego and Tijuana to Brownsville, Texas and Matamoros, Tamaulipas on the Gulf of Mexico. For 1,255 miles of that length, between the Gulf and El Paso/Juarez, the border follows the Rio Grande, known in Mexico as the Rio Bravo del Norte. The remaining 700 miles runs across some of the most forbidding landscape in North America, through the Chihuahuan and Sonoran deserts, until it reaches the less-inhospitable San Diego coast.
Building a wall like the one Trump vaguely describes along this length of border would be a mammoth undertaking. Just the materials going into the wall would have a huge environmental impact, especially with regard to our planet’s beleaguered climate.
Why’s that? Concrete. The building material of choice for modern construction projects would be just about the only practical material for a large wall along the border, especially given the remoteness of much of the border. And that’s one of the few consistent details Trump has offered when asked to describe the wall: he’s said the wall would be built of concrete and rebar.
Concrete has a big greenhouse gas footprint. That’s due in part to the energy it takes to make cement, the ingredient that holds concrete together when it’s mixed, poured, and allowed to dry. Cement is made by heating limestone and clay to 1,400°F, which takes energy, which generally comes from burning fossil fuels. Those fuels account for a bit less than half of the greenhouse gases released in cement production. The rest is released by the limestone as it’s heated, as its main constituent, calcium carbonate, gives off carbon dioxide in a process called calcination.
The world uses a lot of cement, and the industry is responsible for something like five percent of total world greenhouse gas emissions.
What does that mean for the proposed border wall’s greenhouse gas footprint? It’s hard to nail down precisely, both because of the palpable lack of border wall blueprints made available by the Trump campaign and because the proportion of cement in concrete will vary depending on the application.
But let’s take the National Ready Mix Concrete Association’s 2008 estimate of 500 pounds of CO2 released in the production of a typical cubic yard of concrete as a working figure. That’s on the high end of the NRMCA’s estimate range, which runs from 170 to 500 pounds of CO2 per yard of concrete. But it also excludes greenhouse gases released during activities such as shipping of materials, transportation for workers, and fuel for construction machinery.
How many cubic yards of concrete would the wall use? We’ve got the length, but to estimate its volume we’ll need its average height and thickness. Again, Trump has been frustratingly arm-wavy on two of the wall’s three dimensions. His claims about the wall’s height have ranged from 30 to 65 feet, and that’s not counting either foundations or the depth to which the wall would have to extend underground to deter tunneling beneath it.
Let’s call it 55 feet in height, 50 above ground and five below, and ignore foundations for now. How thick would the wall be? Engineer Ali F. Rhuzkan has suggested that since concrete won’t cure well in the heat and aridity of desert summers, that the wall project would likely require local casting facilities to make modular concrete panels eight inches thick, which would be stacked between pylon supports to make a wall 20 feet high. Presumably, a wall 50 feet high could be built in much the same way, though the panels might need to be a bit thicker.
Or perhaps Trump would farm out the design to a low bidder that would suggest pouring the wall in place, with the subsequent quality control issues that have dogged other Trump-branded projects in the past. Let’s take the easy way out, and assume an average thickness of a foot. At 1,954 miles in length and 55 feet high, that would mean the wall contains 63,049,066 cubic yards of concrete.
Which — at 500 pounds of CO2 per cubic yard — means 14,299,304 metric tons of CO2 emitted just to make the concrete in the wall, not counting the foundation, transportation of materials and labor, and other activities.
Then there’s the rebar, the steel reinforcing bars and mesh used to make concrete structures more durable. In order to work at all to reinforce concrete, rebar must make up at least half a percent of the volume of the wall. That would mean at least 315,250 cubic yards of rebar in the wall, more than four billion pounds of steel. The production of that rebar would have a greenhouse gas footprint of at least 800,000 metric tons of CO2, assuming all the rebar was made of recycled steel. (A project this size might well create a shortage of recycled rebar steel, necessitating the use of virgin steel, which has a greenhouse gas footprint about six times higher.)
So that’s more than 22 million metric tons of CO2 released just to make the concrete and rebar in a border wall a foot thick. If the wall’s two feet thick, multiply those results by two.
What’s that mean in real-world emissions? In order to put that much CO2 into the atmosphere with a typical American-made passenger car, you’d need to drive along the border from San Diego to Brownsville, and back, 13.5 million times. The concrete and rebar in the wall would have a greenhouse gas footprint equivalent to about half of all of California’s electrical power plants running for a full year.
We could do similar calculations for the transportation of materials, the construction operations, the energy needed to truck water for concrete and water for cooling equipment and water for keeping workers alive (more than 7,000 acre-feet per foot of thickness, almost the annual demand of the city of Tucson), carbon lost to the atmosphere from clearing desert vegetation for access and perimeter roads, and a bunch of other factors that contribute to the wall’s greenhouse gas footprint. But you get the idea.
In response to inevitable pesky questions about the feasibility of a wall running the entire length of the border, Trump has allowed that it might only be “necessary” to build 1,000 miles of wall, relying on what he called “natural barriers” to deter migration in other stretches. There’s a problem with that approach, which we’ll get into. But for now, if that downsizing does come to pass, the climate footprint of the wall’s concrete would be cut by a little less than half.
But that concession by Trump — that “natural barriers” already block passage across much of the border — hints at one of the biggest problems with the Wall’s likely climate change footprint, and indeed with the other environmental effects we’ll detail in coming segments of this story.
To wit: there’s already a wall, and it’s not working.
Since 1994, when the Clinton Administration launched a Border Patrol program called “Operation Gatekeeper, relying on a combination of walls and “natural barriers” has been the official federal preference for keeping people from crossing the border without permission. Since then, more than 600 miles of the border has been fortified with steel walls, fencing, and other physical barriers intended to keep people out. The existing border wall was built in sections; the first went up in 1994 and subsequent years in the San Diego and El Paso areas. High-tech surveillance equipment went in along the border as soon as it was developed.
The idea was that the Border Patrol would “harden” the easiest parts of the border to cross illegally, the relatively settled urban areas in the borderlands where kids would often play with friends on the “wrong” side of the line, then go home for dinner. The “natural barriers” left unfenced? Some of them were actual physical barriers, such as Tecate Peak in San Diego County and Baja California, where the steepness of the terrain made it next to impossible to cross.
But some of those barriers were subtler, like the 60-plus waterless, arid miles between the border and Interstate 8 in southern Arizona, which the Clinton-era Border Patrol decided would deter migrants from crossing. People crossed anyway, with hundreds of deaths from heatstroke, accidents, and dehydration resulting each year.
In the 2000s, the Border Patrol hardened the border through Organ Pipe Cactus National Monument and the Cabeza Prieta National Wildlife Refuge, which had until then been more or less unsecured, on the Clinton-era assumption that no one would cross 60 miles of waterless desert plain to get to the freeway beyond. That’s when migrants started picking slower, harder, more tortuous and more dangerous routes through nearby waterless mountain ranges instead.
So all the greenhouse gas footprint of Trump’s Border Wall, if it’s ever built, will likely serve no useful purpose even if you support its intention. The border is already walled off with barriers, geographic and technological, that are far more formidable than a silly 50-foot wall. And those barriers aren't stopping people from coming into the U.S. in search of a better life — or for whatever reason.
That’s something to keep in mind as we discuss other environmental harms of the Border Wall in days to come. If the wall is built, those harms would happen for no reason.