Why does artificial light cause so many animal deaths? What makes human-generated noise so destructive to wildlife?
In An Immense World, Ed Yong explores how sensory pollution devastates animal populations worldwide. From bright city lights confusing sea turtle hatchlings to shipping noise disrupting whale communication, human activities are overwhelming animals’ senses in ways we’re only beginning to understand.
Keep reading to discover how we can protect wildlife from sensory pollution and help preserve Earth’s remarkable biodiversity.
Sensory Pollution
Yong argues that, because it can be hard for humans to imagine how other animals perceive the world, we often contribute to sensory pollution, which causes significant damage to all kinds of animals. It forces animals to adapt to attacks on their senses or perish—and for many species, adaptation in a short time frame isn’t possible. Human-caused sensory pollution of animals’ environment is one of the factors contributing to a mass extinction crisis. By understanding how animals sense the world, however, we can help save animals and their environment.
(Shortform note: As outlined in journalist Elizabeth Kolbert’s book The Sixth Extinction, scientists believe we’re in the midst of a sixth mass extinction event. Unlike previous, prehistoric extinctions, the sixth extinction is the result of human activity, including human-caused climate change and ocean acidification, habitat destruction, and the spread of invasive species around the world. In the 50 years from 1970 to 2020 alone, the average size of world wildlife populations has shrunk by 73%, including a 95% decline in Latin America and the Caribbean.)
Human Use of Light Causes Huge Numbers of Animal Deaths
Yong says that humans have artificially lit the night: About 83% of the world lives under light-polluted skies. Blue and white lights are particularly disruptive to animals, but they’re also the cheapest and easiest to produce.
(Shortform note: Blue and white LED lights first became available in the 1990s, and, due to their lower cost, higher energy efficiency, and brighter lighting abilities, they quickly began to replace sodium lamps (which produce a yellow light) in many European streetlights. However, studies show that LED streetlights have significantly increased blue light pollution in Europe. This has resulted in negative changes in animal behavior as well as negative effects on humans’ circadian rhythms and sleep. Researchers say these problems can be mitigated by better lighting design, such as by using LEDs that are less blue-rich and ensuring outdoor lighting is targeted and low-level.)
Human-caused light pollution causes animal deaths on a grand scale, writes Yong. For example, birds die because their migrations are disrupted by bright lights or they crash into brightly lit communications towers. (Shortform note: The number of birds in North America alone has decreased by 30% since 1970, due primarily to habitat loss and climate change, as well as to sensory pollution. Birds are necessary to our economy and food supply because they eat insects that destroy crops, they play a key role in pollination, and they disperse seeds to create new forests.)
Another example of the destructive effects of light pollution can be found in the behavior of sea turtle hatchlings, which die because they can no longer distinguish dark sand dunes from the brighter ocean. (Shortform note: Of the seven species of sea turtles, three are endangered. Sea turtles are critical to maintaining a healthy ocean and fisheries, in part because they maintain the sea grass that provides a habitat to various species of fish.)
Yong says that artificial light may also be contributing to the massive global decline in insects—which could seem like a good thing, but it can alter entire ecosystems. For example, an experiment in which street lights were installed in remote Swiss meadows showed that flowers in those meadows were visited by pollinating insects 62% less frequently than in non-illuminated meadows.
(Shortform note: Research shows that in the last four decades, there has been about a 45% decline in insect populations. Yet insects are the base of the entire food chain, feeding birds, reptiles, and small mammals, which in turn provide food for larger animals. Insects are also crucial to agriculture: They pollinate more than 75% of crops, at a value of up to $577 billion a year. They also act as the world’s cleaning crew by decomposing waste and organic matter. For example, dung beetles are worth about $380 million a year to the US cattle industry because they break down manure and churn rangeland soil.)
Noisy Human Activities Have Degraded Animal Ecosystems
Human activities such as transportation and construction have also altered our quiet places. Human activities have doubled the background noise in 63% of protected spaces (such as national parks).
Yong explains that this affects animals in many ways. Birds have difficulty finding mates because their songs aren’t loud enough to be heard over human noise. Various animals can no longer hear their prey or predators, which can cause them to lose weight and become weaker, or to abandon their normal habitat altogether. Unfortunately, there isn’t always a quieter place for them to go, as 83% of the continental US is less than a mile from a road.
(Shortform note: Other effects of noise pollution on animal behavior include difficulty navigating, reproducing, finding food, and communicating. Noise pollution can cause animals stress, fear, pain, and hearing damage; studies show that long-term exposure to loud noise reduces memory and learning ability in some animals. These effects, in turn, impact animals’ survival, contributing to the decrease in wildlife populations across species.)
The oceans have also gotten much louder, says Yong. Between World War II and 2008, global shipping has made low-frequency noise 32 times louder. This can affect marine animals in all sorts of ways; whales, for example, stop singing and crabs stop eating.
| How Ocean Noise Pollution Endangers Marine Life The effects of human-caused ocean noise on marine animals’ behavior—and survival—are even more extensive than Yong describes. In addition to global shipping, ocean noise is caused by ship sonar and seismic air gun blasts used in oil and gas exploration. Air guns fire every 10 seconds day and night for months at a time, producing the loudest noise of all, at up to 260 underwater decibels. Container ships reach up to 190 underwater decibels. These sounds equal about 200 and 130 decibels in the atmosphere, respectively; by comparison, the launch of a space shuttle is about 160 decibels. And sound travels underwater much faster and farther than in the air. Scientists say these noises can kill marine life gradually or even instantly in the case of zooplankton such as krill, which form the basis of the whale’s diet. Human-caused ocean noises also decrease marine animals’ reproduction, alter migration, impair hearing, cause brain hemorrhaging, and mask communication sounds necessary for survival. Ocean noise pollution has a particularly severe impact on whales and dolphins, who use echolocation to hunt, navigate, find mates, and communicate with one another. |
Human Activity Impacts Every Other Animal Sense
Besides vision and hearing, every other animal sense is also impacted by human activity. Yong cites a few examples: Bats crash into windows because smooth vertical surfaces, which don’t exist in nature, produce echoes that sound like open air. About 90% of seabirds eventually swallow plastic because it contains DMS. DMS is also precisely the smell that—when it occurs naturally—helps seabirds locate krill.
(Shortform note: Researchers have identified three ways in which sensory pollution impacts species fitness (defined as their mortality and ability to reproduce): misleading, distraction, and masking. Bats’ and seabirds’ responses to sensory pollution are examples of misleading, which happens when an animal reacts to a sensory pollutant as if it’s a natural signal. Distraction occurs when an animal’s attention is taken away from what it’s doing, as when traffic sounds distract an animal from hunting. Masking is when sensory pollution overwhelms the stimuli in the natural environment, as when whales can’t hear each other’s songs due to all the ocean noise generated by human activity.)
Humans Can Reduce Sensory Pollution to Help Save Animals and the Environment
Yong argues that understanding how animals sense the environment can help us save it. He adds that, unlike other more permanent types of pollution, such as chemical or radioactive pollution, sensory pollution can be addressed quickly and easily by simply removing the sensory stimuli that humans have added to the natural environment.
There are many simple ways to reduce sensory pollution, but economic and political incentives don’t always exist to make these changes. Examples of changes we could make to protect animals and ecosystems include sound-absorbing berms, porous pavements that absorb vehicle noise, and quieter hulls and propellers on commercial ships (already used in military ships). Even basic measures such as requiring vehicles to slow down in key wilderness or ocean areas can make a huge difference. For example, a 2007 study showed that when commercial ships slowed down by 12%, they produced half as much noise.
(Shortform note: Because sensory pollution is only one of many factors affecting the recent drastic decline in biodiversity, animal species’ survival can also benefit greatly from any efforts to address other factors. For example, warming air and ocean temperatures caused by climate change can shrink or destroy animal habitats; however, we can slow climate change by curbing fossil fuel emissions. In How the World Really Works, scientist Vaclav Smil argues that, while the world is heavily reliant on fossil fuels, there are still many actions governments and individuals can take to reduce emissions, including better home insulation, land and forest conservation, transitioning to electric vehicles, cutting down on food waste, generating electricity from renewable sources, and using nuclear energy.)
Other measures to address sensory pollution are more complex, says Yong. For example, when a heat wave caused a major bleaching event on the Great Barrier Reef, a marine biologist discovered that by playing the sounds of a healthy reef over a loudspeaker, he could attract baby fish back to the reef. While this isn’t a practical solution to implement on a large scale, with over half of the Great Barrier Reef gone, even small solutions help.
Yong points out that the only reason scientists could implement this solution at all is because there are still healthy reefs where they could record underwater sounds. He says that as long as such places exist, we can still save them.
| Why Should We Save Animals and Their Habitats? Throughout An Immense World, Yong focuses on the intrinsic value of animals and the ethical argument that, because human activities cause animals harm, we have a moral imperative to save animals from harm. As he suggests, however, not everyone sees the intrinsic value of a frog or a bee. Some argue that protecting animals and their habitats may have negative economic consequences, such as limitations on land development and resource extraction, increased transportation and industrial costs, or job loss. Aside from suggesting some economically viable solutions to sensory pollution, Yong doesn’t address these arguments. But a large body of scientific research indicates that wildlife conservation and preserving biodiversity doesn’t just benefit animals, it also benefits humans: —data indicates that biodiversity is essential to our food security, our health, and our economy: 1. Food security. Each species plays a unique role in its ecosystem, contributing to the overall health and stability of its environment. The loss of a single species can disrupt ecological balance, leading to negative cascading effects on other species and ecosystem functions. Pollinators such as bees are a primary example of this: Their extinction would drastically affect plant reproduction, which, in turn, would severely reduce our food supplies. 2. Health. Biodiversity helps protect against disease. Research shows that 60% of infectious diseases come from animals. With human activities expanding into animal habitats, animals are forced to live closer to each other and to humans, leading to the spread of zoonotic diseases. Conversely, protecting natural ecosystems leads to lower instances of diseases such as Lyme disease and malaria. 3. Economy. Research shows that more than half of the world’s Gross Domestic Product (GDP) is dependent on nature. Businesses that rely directly on animals and their habitats run the gamut from wildlife tourism to commercial fishing. Natural ecosystems also provide jobs for billions of people globally. |
Exercise: Consider How Your Activities Affect Animals’ Senses
Yong argues that understanding how animals perceive the world can help us reduce sensory pollution and save threatened animals. While some solutions to sensory pollution require systemic changes to law and policy, individuals can also make a difference. Consider how you could alter your own activities to decrease sensory pollution.
- Identify the animals that live in your area. If you live in the city, are there urban wildlife nearby such as squirrels, coyotes, crows, or rats? If you live in the country, are there animals such as foxes, bobcats, wild turkeys, or hawks?
- Identify some of your activities that might affect these animals’ senses, and consider the ways in which they might do so. For example, do you use outdoor floodlights or other night lights that could affect bird migration; leave out trash that could appeal to local wildlife’s sense of smell, potentially disrupting their diets; or use loud leaf blowers that could overwhelm animals’ hearing and cause them to abandon their habitat?
- Finally, consider how you could alter your activities to decrease sensory pollution. For example, you might consider using your outdoor lights only when necessary, rather than leaving them on all night; ensuring your garbage cans are well sealed; or using electric leaf blowers.
