Beyond the Human Umwelt: Silent and Invisible Sensory Pollution
September 18, 2026
Aldo Leopold famously wrote, “The penalty of an ecological education is that one lives alone in a world of wounds. Much of the damage inflicted on land is quite invisible to laymen.” Today we might say that the penalty of an education in sensory biology is the awareness that much of the damage inflicted on land is quite invisible to humans.
Pit vipers use their ability to sense infrared radiation to locate warm-bodied prey, photo by Bernard Dupont / CC BY-SA 2.0
Biologist Jakob Johann von Uexküll coined the term Umwelt to refer to the environment as it is experienced by a given organism, via the information available to that organism’s senses. Our human Umwelten do not necessarily represent the world as other animals perceive it. Indeed, we completely lack certain senses found in many other species. Many birds are sensitive to the Earth’s magnetic field and the polarization of light, using these cues to guide their migratory journeys. Some snakes rely on infrared sensing to hunt. Shorebirds and ibises use a sense of “remote touch” to detect buried prey. Fish employ their lateral line system to detect objects and movement at a distance through the water. Some species of fish can detect electric fields, and insects can sense electrostatic fields. The list could go on.
Unfortunately, conservation has yet to catch up with the science of sensory biology. As Ed Yong writes at the end of An Immense World, a best-selling, popular science overview of the study of non-human Umwelten, “We are closer than ever to understanding what it is like to be another animal, but we have made it harder than ever for other animals to be.”
Honey bee, photo by Kate McFarland
Implicit Anthropocentric Bias
No matter the extent of our ecological education, our unaided senses cannot reveal the full extent to which anthropogenic activities disrupt the lives of wild creatures, and this bias afflicts the rewilding movement. I am no exception. Like many, I have often defaulted to talking only about light and noise when raising the topic of sensory pollution. This is covertly anthropocentric: Light and noise are salient because they annoy me in my human Umwelt.
Even when we do speak of noise and light pollution, we should be mindful of our sensory biases. Many animals can hear frequencies inaudible to humans, and thus they are vulnerable to have their communication masked by noise that we cannot hear. Whales, elephants, and giraffes communicate in infrasonic frequencies. Some other animals, like mice and rats, use calls at frequencies higher than the range of human hearing. Similarly, light pollution can occur in the ultraviolet spectrum, visible to many birds and bees.
A different form of light pollution that’s invisible to humans is polarized light pollution. Sunlight becomes horizontally polarized when it is reflected by flat surfaces. For hundreds of millions of years, water bodies were the main source of horizontally polarized light on Earth, and some aquatic insects evolved a sensitivity to polarized light that allows them to locate water. In the modern built world, however, artificial surfaces such as asphalt and solar panels polarize light in a similar way – creating an ecological trap that lures insects to unsuitable habitat.
Flat surfaces like asphalt reflect horizontally polarized light, attracting insects who mistake it for water, photo by David H. Funk / Wikimedia, CC BY 3.0
The Olfactory Landscape
Outside of light and noise, one of the better studied forms of sensory pollution is olfactory pollution. In a 2022 article, ecologist Patrick Finnerty and colleagues introduced the concept of the olfactory landscape and describe several ways in which scents can be expected to influence movement ecology. As they describe it, “At any one time, an animal is faced with overlapping odor contours emitted from sources of risk (predators, parasitic infected and/or territorial conspecifics) and reward (mating opportunities, food). […] For an animal navigating its surroundings, these dynamic contours of odor can be exploited, providing information on the spatiotemporal distribution of potential threats and opportunities.”
The authors do not discuss olfactory pollution, however, even though they consider the possibility of deliberately adding scents to landscapes to influence animal movements as part of conservation management strategies (e.g. to nudge grazers away from sensitive flora or predators away from livestock or protected prey species).
Engineer Romain Sordello and coauthors raise the issue of olfactory pollution in their 2025 “Manifesto for multidimensional ecological networks,” in which they call for an “olfactory infrastructure” where anthropogenic odors are reduced at their source. They note that “anthropogenic odors are likely to interfere with the olfactory communication of living organisms, by decreasing the intensity of signals or by luring individuals with wrong information.”
Bumblebee, photo by Kate McFarland
To date, the majority of studies of “odor pollution” have focused on insects’ use of floral odors during pollination. Air pollutants such as ozone degrade the scents emitted from flowers, which pollinators use to find them. Research has suggested, for example, that exhaust pollution can interfere with honeybees’ ability to locate flowers, volatile organic compounds (VOCs) released by fungicides can inhibit bumblebees from recognizing floral scents, and ozone pollution can reduce the ability of fig trees to attract the fig wasps that uniquely pollinate them. Industrial and automotive pollution can also mask the scents of flowers from nocturnal pollinators like moths. In the words of neuroscientist Jeff Riffell, who researched the effects of the degradation of floral odors by nitrogen oxide pollution, “It’s almost like the moths had COVID.”
Pollination has been most studied due to its economic importance, but VOCs emitted by plants play other ecological roles as well, such as deterring herbivores and communicating with other plants. Thus, we might expect even more wide-ranging effects of odor pollution.
VOCs also play important roles in communication between animals. Pheromones enable some animals not only to attract mates but also to recognize other individuals of the same species. In an interesting but concerning study published in Nature Communications in 2024, ethologists at the Max Planck Institute found that ozone pollution interferes with the pheromones of drosophilid flies, leading some individuals to get confused and mate with members of other species, sometimes resulting in sterile offspring.
European robin, photo by Kate McFarland
Functional Fragmentation Revisited
In my recent Rewilding Earth article on terrestrial noise pollution, I emphasized the concept of functional fragmentation. Busy roads, for example, present more than physical barriers to animal movement; the noise of traffic alone can cause some animals to avoid otherwise suitable habitat, sometimes with knock-on consequences for ecosystems.
We can now see that functional fragmentation can occur in other sensory modalities too. If animals rely on smell to navigate olfactory landscapes — such as bees and moths locating flowers — then busy roads functionally fragment the landscape via a second mechanism: exhaust pollution that degrades olfactory information.
Another recently studied phenomenon is electromagnetic pollution, which can potentially pose a functional barrier to migratory birds and bats. Experiments suggest that the levels of electromagnetic radiation present in many modern cities are enough to disorient migratory birds (such as European robins) and bats (like soprano pipistrelle bats). (It should be noted that, while a disorienting effect of electromagnetic noise has been observed in laboratory settings, evidence of its impact in the wild is still lacking.)
A study published in Science shows that manmade electromagnetic noise can disorient pipistrelle bats hours after exposure, photo by John Purvis / CC BY-NC-SA 2.0
That said, electromagnetic pollution might present additional adverse effects on animals with a sense of magnetoreception, beyond masking cues used to orient during migration. For example, one recent study found that anthropogenic magnetic fields appear to impede the ability of zebrafish to react to visual stimuli. This is an example of what is sometimes called cross-modal distraction, and it’s a phenomenon with which we’re all familiar. Imagine, for example, that you’re trying to solve a crossword puzzle, but a car alarm is blaring outside. You don’t need hearing to complete a crossword puzzle; nonetheless, the obtrusive auditory signal might make it hard to think straight. Now imagine that you’re also attuned to magnetic fields, the scent of numerous VOCs, electrostatic fields, ultrasound or infrasound, minute changes in temperature or humidity… What other stimuli might you find obnoxiously distracting in our industrialized landscapes? It is hard for us humans to fathom.
Since Leopold’s time, the conservation movement has helped to open the eyes of “laymen” to ecological damage done to our landscapes. Even so, our human senses can’t reveal the full scope of the degradation. We must not be deaf and blind to the importance of animal senses outside of hearing and vision and, correspondingly, sensory pollution beyond noise and light.
A study published in Scientific Reports found that magnoreceptive zebrafish become distracted from tasks when exposed to a low-frequency magnetic field, photo by Stephen Ward / Wikimedia, CC BY-SA 2.0
Kate McFarland is a former board member of The Rewilding Institute. Her rewilding-related interests subsequently settled on feathered fauna and flyway conservation, with accompanying interests in noise and light pollution mitigation, as well as non-anthropocentric conservation ethics.
