One of the most noticeable aspects of Bernie Krause is his oversized glasses, which draw attention to his keen eyes. Ironically, Krause has dedicated his life to listening rather than seeing. His vision impairment led him to explore the world of sound—first through music, then through the natural symphonies of the environment. Over the past fifty years, he has recorded the biological orchestrations to which many remain oblivious.

Krause's exceptional ability to listen contrasts with the common societal emphasis on sight. We often find ourselves asking what we saw during nature walks, while the soothing sounds of birds and rustling leaves fade into the background. This tendency to overlook auditory experiences is not just personal; it mirrors a broader scientific trend. While researchers have studied specific animal sounds, Krause and others in soundscape ecology argue that traditional bioacoustics misses the larger picture. Their microphones serve as stethoscopes, capturing the exchanges between humanity and nature.

“The natural world’s voice provides insight into our role within the ecosystem and our impact on it,” Krause asserts. “It reveals our relationship with the environment and indicates our ecological status.”

In this era known as the Anthropocene, marked by significant human impact on Earth, we have various tools to assess our ecological footprint. Typically, these tools rely on visual observations, focusing on specific species and land use changes via satellite imagery.

Krause believes that true ecological measurements should involve listening to natural soundscapes. He has compiled an extensive collection of nature’s sounds, emphasizing that they are more than mere recordings of individual species. He criticizes the traditional focus of bioacoustics as being “decontextualized and fragmented,” likening it to trying to understand a symphony by isolating a single instrument. “Removing one part from a performance diminishes the overall experience,” he explains.

Krause has certainly recorded various species—from seals echoing geomagnetic storms to baboons resonating in stone amphitheaters—but these recordings serve to capture entire ecosystems rather than individual animals.

In his studio, nestled in a California hillside, he shares some of his favorite recordings: sounds from a Florida swamp, an ancient forest in Zimbabwe, coastal mangroves in Costa Rica, and a Sierra Nevada meadow. As the sounds fill the room, spectrograms display the frequency and timing of each note, resembling musical scores.

He notes an intriguing phenomenon: despite the complexity of sounds, they rarely overlap. Each species occupies its distinct frequency range, fitting together harmoniously—much like pieces in an intricate puzzle. Krause coined the term "biophony" to describe this rich tapestry of life’s sounds, which reflects a coevolution of species over time in specific habitats. A vibrant ecosystem allows each species to find its unique sonic space.

“The biophony embodies the essence of life in a habitat,” he remarks. “In a thriving environment, all species locate a niche for their voices.” He plays a recording of an ancient Borneo rainforest, where bats, cicadas, and various birds occupy their designated frequencies.

Zooming in on the spectrogram, each call appears as distinct dots, akin to constellations. “This representation showcases a universe of life,” he says, marveling at its complexity. “It reveals the age and richness of this ecosystem.”

Initially, Krause's insights took time to gain traction within the scientific community. Not a traditional scientist, he has a background as a musician, having performed at Carnegie Hall and contributed to early electronic music.

His concept of biophony resonated with ecologist Stuart Gage, who sought to use sounds for ecological assessment. Together, they recorded Sequoia National Park and explored acoustic complexity as a means to gauge species diversity. This initial collaboration paved the way for the growth of soundscape ecology, which has flourished due to advancements in recording technology.

Researchers now document numerous landscapes globally, converting extensive sound recordings into numerical indicators of ecological health and human impact. While these indices are still in development, Krause’s niche hypothesis remains a theory awaiting validation. “The day will come when we can listen to an ecosystem’s health,” predicts Bryan Pijanowski, a soundscape ecologist.

For Krause, the act of listening is profoundly significant. Current ecological indices vary in complexity, from simple counts of animal calls to more nuanced measures that align with Krause’s biophony concept. Researchers like Jérôme Sueur are quantifying species diversity, while others, including Almo Farina, analyze patterns of birdsong to assess habitat health.

Krause is particularly attuned to the impact of human-generated noise, which can drown out natural sounds. Traditional bioacoustics often focuses on how this noise affects individual species, while soundscape ecology examines its effects across entire communities.

Despite the potential for sound indices to offer insights into ecological health, Krause observes that nearly half of the habitats he has recorded are now compromised, primarily due to human activity. “Listening reveals the stark reality of our changing world,” he states. “As nature becomes quieter, we must ask ourselves: Is this what we desire?”

Krause is a pioneer in soundscape ecology, having developed the niche hypothesis and contributed significantly to the field. However, he remains committed to the authentic act of listening rather than relying solely on technology.

On a cool March morning, he takes me to Sugarloaf Ridge State Park, a site he has recorded since the 1990s. As we ascend the trail, the morning sky comes alive with stars.

The park, home to an observatory, is rich in biodiversity. Krause sets up his equipment in a prime location, prepared to capture the dawn chorus—a universal celebration of life that occurs across habitats at daybreak.

The reason behind this chorus remains elusive. Various theories suggest it serves territorial purposes or is a result of the unique acoustics of the morning air. Nature recorder Martyn Stewart likens it to a “newspaper being read in many languages.”

Soon, a scrub jay starts the performance, joined by other birds. The chorus becomes a rich tapestry of sounds, with each species contributing its unique note. Krause, however, expresses disappointment that the chorus isn’t as vibrant as in years past, perhaps due to environmental changes.

Still, the concert remains extraordinary. The sounds blend beautifully, and while distant jets are audible, they don’t disrupt the harmony. Sugarloaf may not be untouched, but it is protected, allowing life to flourish amidst urban encroachment.

Krause notes, “Though less robust than in previous years, this chorus is still a hopeful testament to seasonal life.” While he mourns the loss of many soundscapes, he remains optimistic about the potential for conservation and recovery. “Wherever we allow it, life can thrive—if only we would listen.”

Brandon Keim is a freelance journalist specializing in science, technology, and nature, with work featured in various prominent publications.

Originally published at Nautilus on April 10, 2014.