On Jan. 25, President Trump signed an executive order instructing construction to begin on a wall along the U.S.-Mexico border. Environmentalists and civil rights activists say the proposed wall on the southern border with Mexico is a threat to the environmental rights of the people who live on both sides of the border."When you have such beautiful wilderness areas as we have here in Arizona, the idea of putting this large wall that prevents the migration of animals, that scars the earth itself, and especially knowing how ineffectual it is, is something that is just sad," said Juanita Molina, the executive director of Border Action Network, an organization that advocates for the health and wellness of people who live along the border. "The reality is that border communities are porous by nature."Molina, who lives in Benson, Ariz., said the wall could cause flooding and debris build-up on both sides of the border. (Chris Clarke of KCET has reported that a concrete wall "would cause catastrophic flooding in the desert.") Molina also said there could be legal and ethical consequences if people try to build on the land of the Tohono O'odham Nation, whose reservation straddles the border, and whose leaders have spoken out for years against a border wall. But even if no part of the wall materializes, she said, the rhetoric around it has already caused rifts in her community."I think that there's a polarization that's happening in our communities now that hasn't happened in many years," Molina said. "The mistrust and the racial divides are very present...This isn't the first time that the establishment hasn't supported our views as a community or supported our views as people of color...Our laws, our freedoms, our cultural evolution is something that is part of our everyday lives and struggle."As of 2010, there were about 15 million people living in border counties on both sides of the Mexico-U.S. border, according to the Wilson Center's State of the Border Report. If growth rates stay the same, the report says, that number is likely to reach 29 million in 30 years.In the four border states on the U.S. side, Texas, California, New Mexico and Arizona, people of Mexican origin make up at least a quarter of the total population, with higher concentrations in counties within 100 kilometers of the divide. In El Paso, Texas, for example, Latinos, primarily of Mexican descent, make up more than 80 percent of the population.According to Raul Garcia, who works at the environmental justice law firm Earthjustice, it's no accident that the border wall would primarily affect people of color. "With Trump's militarization of the border, he's specifically targeting immigrants and Latinos trying to make a life for themselves and their families," Garcia said. He said that communities of color all over the U.S. face similar challenges.Garcia pointed to issues like the water crisis in Flint, Mich., and construction of the Dakota Access Pipeline in South Dakota, where other communities of color have been singularly affected by environmental issues. "We also see it throughout our country when highways are built and minority communities, like Latinos and blacks, are divided and displaced to make way for the privileged upper class folks on the other side of the city," he said.Ira Mehlman, of the Federation for American Immigration Reform, supports the construction of the wall and said that it is an important tool for impeding illegal immigration. He said that FAIR supported the Secure Fence Act in 2006, which authorized construction of a border barrier — legislation, he pointed out, that had support from people like Hillary Clinton, Chuck Schumer and Barack Obama.In terms of environmental risks, Mehlman said that while a wall could have some environmental impact, "so [do] tens, hundreds of thousands trampling across the flora, leaving tons of garbage and debris along the way. So having that traffic is also damaging to the local ecology."But scientists and environmentalists have been warning about the potential negative environmental effects, like restricted animal movement and plant pollination, of a border wall for over a decade, since President George W. Bush signed the Secure Fence Act of 2006. When Donald Trump started discussing the construction of a full-scale border wall during his presidential campaign, those concerns resurfaced.In September 2016, Sergio Avila-Villegas, a conservation scientist at the Arizona-Sonora Desert Museum, told BBC's Science in Action team that "Border infrastructure not only blocks the movement of wildlife, but... destroys the habitats, fragments the habitats and the connectivity that these animals use to move from one place to another."George Frisvold, a professor at the University of Arizona who specializes in environmental policy, said that politically speaking, a border wall "gives this false impression that you're actually doing something, but it has this political attraction because it's completely ineffective" in preventing problems associated with immigration. Environmentally, he said, "Any time you're going to put big structures along the border, and usually it isn't just the structure out there by itself — you have to have some sort of access road for people to go get to it, so you're going to be tearing up natural habitat with structures and roads, and that's going to be disruptive."Mark Magana, the president of GreenLatinos, said he sees Latinos, especially millennials, becoming more involved in the environmental rights movement. He said many Latinos were raised to be cultural conservationists. "[We] grew up respecting, conserving, reusing, re-purposing, being very respectful for what we have," he said. "And that is not because I read about it or...I claim to be an environmentalist. It's because that's what our grandmother taught us...You know, 'Don't turn on the air conditioning. Reuse that piece of aluminum foil...Eat every part of the animal...Find a way to fix that.'"And we have, whether it's because of an agrarian ancestry or because of poverty, many cultures like Latinos have developed this natural culture of conservation. And it's just a respect we have for the little that we have."Earlier this month, Congresswoman Michelle Lujan Grisham introduced the "Build Bridges Not Walls Act," which would prohibit Trump's executive order. So far, it's been endorsed by 59 members of Congress and the Congressional Hispanic Caucus. Copyright 2017 NPR. To see more, visit http://www.npr.org/.