The US‐Mexico borderlands used to host a wide range of natural and social environments, many of which have become irreversibly altered by the structures built to reinforce geopolitical boundaries. To rethink the form and purpose of these borderlands is a political objective of utmost importance, yet most future thinking about the border has remained restricted to imagining new versions of border walls euphemistically rebranded as “sustainable” alternatives. This essay analyzes the limitations of popular design projects that effectively greenwash the securitization imperative of the nation‐state. It then turns to a lesser‐known speculative project that reimagines the borderlands from the perspective of underground tunnels through a multimedia model. The essay draws on the insights of critical environmental media studies to illustrate the affordances of specific media forms for articulating future worlds with a greater focus on care. This analysis proposes ruinous speculation as an affirmative form of future thinking that orients toward infrastructures that enable human and nonhuman worlds to thrive and away from infrastructures that reinforce the violent hierarchies of the geopolitical divide.