Humans can accurately perceive biodiversity through the senses

People don’t need training to pick up on biodiversity – just eyes and ears. A new study finds their snap judgments about forest richness match the numbers ecologists collect in the field.

Thus, our everyday senses give a surprisingly accurate readout of nature’s true diversity, a talent that may help explain why greener, livelier places lift our mood.

The research was led by experts at the German Center for Integrative Biodiversity Research (iDiv).

The team asked volunteers with no ecology background to sort forest photos and sound clips by how “diverse” they felt. Researchers then compared those gut rankings with bird counts and detailed vegetation surveys from the same sites.

Our senses detect biodiversity well

Forty-eight adults completed a visual session using fifty-seven photographs taken in mixed-species woodlands across Germany, Belgium, and Poland. Another 48 adults listened to sixteen 10-second audio recordings from the same patches.

The participants first grouped the images or sounds any way they liked, revealing the features that stood out to them, and then rearranged the material from low to high biodiversity.

The researchers measured the real complexity of each forest in two ways. For pictures they combined tree-species richness, canopy structure, understory structure, and ground-layer cover into a single “actual diversity” score.

For sound they simply counted the different bird species singing in each clip. When the numbers were compared, perceived and measured diversity moved together: a strong correlation of 0.76 for sight and an even stronger 0.87 for sound.

Lushness hints at species count

When volunteers explained their choices, they kept coming back to elements any hiker would notice. Dense foliage, dappled light, bright greens, and a mix of trunks signaled a thriving community.

Using simple image analysis, the team confirmed that a higher “greenness index” matched both the on-the-ground surveys and the ratings people gave.

In other words, the greener the shot, the richer the habitat and the higher the score. By contrast, photos that looked washed-out or evenly lit tended to come from simpler, species-poor areas.

Hearing biodiversity’s quiet signals

Sound told the same story through a different sense. Listeners paid closest attention to birdsong – its complexity, pitch range, volume, and rhythmic patterns.

Four standard acoustic indices, including the well-known Acoustic Complexity Index, rose in lockstep with both perceived richness and the tally of bird species.

Even without technical tools, participants homed in on the same signals: lively, layered choruses meant lots of birds, while sparse or repetitive calls hinted at poorer sites.

Perception and wellness connect

Earlier studies show that how biodiverse a place feels has a stronger link to mental health than the species list on a clipboard. That connection motivated the new work.

Lead author Kevin Rozario, a scientist at iDiv, emphasized the value of understanding how people sense biodiversity.

“It’s important to identify what people perceive with regards to biodiversity, what the contribution of the different senses could be, and under which circumstances people’s perception of biodiversity best aligns with what ecologists measure.”

Rozario noted that perceived biodiversity is thought to play a role in supporting mental health. The new data reveal that alignment is often tight, at least when people can compare several settings side by side.

Biodiversity loss hits the senses

The study also underscores a cultural loss that runs alongside species decline. “Not only are we experiencing an extinction of species, but also an extinction of biodiverse experiences,” Rozario explained.

City living, indoor jobs, and digital leisure mean fewer chances to stand among varied trees or wake to a dawn chorus. Preserving those encounters may matter for public health as much as for conservation biology.

Forest planning with people in mind

One clear takeaway is that mixed forests with layered canopies and active birdlife satisfy both ecological targets and human senses.

“We recommend to conserve and restore diverse forests characterized by a variety of tree species and structures to also provide habitats for different vocalizing bird species,” Rozario said.

“These conservation measures will have the dual benefit of meeting conservation goals while also increasing people’s experience of biodiversity and therefore likely increasing mental wellbeing.”

Planners can even use quick proxies. A handheld camera that registers shades of green, or a portable recorder that crunches acoustic indices, offers a cheap way to flag sites that feel and are alive.

Urban designers might favor plantings that stay green through the year or host birds with distinctive songs, boosting the sensory richness visitors notice.

Building a multisensory picture

The study relied mainly on young, university-educated women and on brief comparisons rather than lone encounters.

Future work will test broader groups and real-time walks to learn how age, culture, and context shape perception.

Researchers also hope to add smell, touch, and even temperature to build a full, multi-sensory picture of how humans read living landscapes.

For now, the message is clear. Ordinary observers, armed with nothing more than eyes and ears, can still spot the difference between a sparse wood and a thriving one – and that instinct lines up with hard science.

Protect the layered greenery and the singing birds, and you protect both biodiversity and the quiet joy people draw from it.

The study is published in the British Ecological Society journal People and Nature.

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