Do you remember those first moments in Pixar’s WALL-E? The city is deserted and lifeless, buried under mountains of garbage. Only a robot remains, silently stacking trash compressed into cubes, carrying on alone in a world void of life. WALL-E ‘s terrifying vision of Earth isn’t just imaginative fiction – it’s a scientifically accurate prediction of the result of long-term superfluous consumerism and unattended waste. 

The first thing you notice in WALL-E ’s world is the sky – or rather the lack of one. It’s a perpetual yellow-brown haze, similar to the sky Los Angeles saw in September of 2020, known as photochemical smog.

Photochemical smog requires strong sunlight to form – a prevailing circumstance in WALL-E ’s world, where the protective stratospheric ozone layer has long been destroyed, allowing high levels of ultraviolet radiation to bake the surface of the Earth. The primary pollutants for the smog – nitrogen oxides and volatile organic compounds – have accumulated from the centuries of industrial activity and mass consumption that smother the planet. Intense sunlight breaks down these pollutants, driving the chemical reactions that create toxic ground-level ozone (O₃), the smog’s primary component. This creates a devastating circumstance: the shielding ozone layer is gone, while the poisonous ground-level ozone is continuously regenerated. In WALL-E, this process has reached a terminal state – the Sun continuously generates new smog from the vast reservoir of pollution, creating a self-sustaining toxic atmosphere. 

Another major component of smog is particulate matter, a mixture of solid particles and liquid droplets in the air, varying in size and composition. While some particles like dust and smoke are visible, others are microscopic and can be inhaled, leading to critical health conditions. The most dangerous particles are categorised by size: PM10 (10 micrometers or less) and the smaller PM2.5 (2.5 micrometers or less), which can penetrate deep into the lungs and enter the bloodstream, triggering cardiovascular and respiratory diseases. This explains the lack of life on Earth – humans, knowing the hazards of living on the planet, promptly escaped into outer space, and the remaining populations of living organisms collectively suffered from the pollution and went extinct. 

Since such air clearly creates an uninhabitable environment for all life, it is surprising that Hal, WALL-E’s cockroach friend, is alive. WALL-E depicts cockroaches as extremely resilient creatures, embodying the common myth that they will outlive humanity and even nuclear war (given that their food supply doesn’t run short). In the film, Hal is stepped on, squished, and blasted, but comes out alive, barely injured, every time. But how?

A possible explanation is that cockroaches underwent accelerated evolution. Over the seven hundred years Earth was abandoned, immense evolutionary pressure would have caused directional selection in the surviving roaches, favouring only the most resilient individuals. Directional selection is a type of natural selection where one extreme phenotype is favoured, shifting the population’s average phenotype. Take the peppered moths during the Industrial Revolution in the late-18th century . Before industrialisation, light-coloured peppered moths were predominant, camouflaged against pale lichen-covered trees. After industrial pollution darkened tree trunks with soot, dark-coloured peppered moths became favoured and predominant to blend in with its new landscape. Similarly, in a post-abandonment Earth covered in emitted debris, cockroaches with extremely sturdy exoskeletons would have survived. 

Hal’s lineage likely developed a series of adaptations for survival. One possible adaptation is a crush-resistant exoskeleton. Achieved through mutations in genes responsible for chitin structure and sclerotisation, it would produce a carapace with superior tensile strength and elasticity, allowing the cockroach to withstand significant compressive forces from being squished. A second adaptation features a more advanced internal hydrostatic skeleton. Mutations that allow the organism to quickly increase the pressure in its haemocoel transform the body into a sturdy, fluid-filled support system. In this way, it can actively resist compression. A third adaptation is that their inherent flattened, dorsoventrally compressed body form would have been hyper-specialised. This specialised shape helps laterally distribute any force from above, so when something presses down, such as a footstep, the body is not simply crushed. Instead, it pushes outward into the softer material nearby, avoiding direct squashing.

I think Pixar’s WALL-E challenges us to see our present choices not as isolated moments, but as forces that can shape the very habitability of Earth’s future. Although it’s fascinating, our goal should not be to prove that life can adapt on barren wastelands, but instead to preserve a world where such adaptation is never necessary.