If you’ve spent time on a winter walk over the festive period, chances are the exercise has been interrupted by you or one of your companions taking out a phone to identify the sound of a nearby bird. But if Merlin, ChirpoMatic and similar apps identifying bird calls have become ubiquitous additions to any encounter with nature, for Professor Hans Slabbekoorn they’re not nearly popular enough.
“I think it’s incredibly important, but I think that most of those people would be the ones that are going out for walks in the woods anyway. There is a group of people that are interested, and there is a big part that will never be interested and will not see the value, but the big chunk in the middle is what I think I should focus on.”
For Hans, birdsong is not a recent novelty, but the focus of a lifetime’s research into the soundscape of the natural world, its role in animal communication, and the impact of humanity.
“Acoustic ecology is the understanding of the acoustic diversity in the world,” he explains.
“All the biodiversity that’s around, and the sounds they make, can be investigated from an ecological perspective. And that means it matters how they produce the sounds, how they perceive the sounds, how these sounds come from one individual to another through the environment, and also how it has evolved over time. All these factors play a role in my discipline. The world is of course not the same anymore – it has always been dynamic, but especially acoustically there’s a lot of anthropogenic noise that has relatively recently changed this field a lot.”
After studying Biology at the University of Utrecht, Hans completed his PhD at the University of Leiden, exploring acoustics and avian communication. A postdoc opportunity in Cameroon, where he investigated why birds in rainforests sing in a lower frequency than those outside the forest cemented his fascination.
“That’s when I started to really understand not only that the animals communicate with each other, but that the environment is incredibly important in understanding how they communicate with each other. First, I thought I would focus on the density of the vegetation that filters out particular frequencies, but it was so loud in the forest that I couldn’t hear the sounds that I was playing back!”
A year’s fieldwork in Cameroon was followed by three years of data processing and writing papers in San Francisco, before he returned to the Netherlands and established himself in the Institute of Biology at Leiden University. His research has expanded, in recent years, to include the sounds made by fish, and the acoustic impact of shipping and the offshore energy transition on the marine environment.
“My last six PhD students were all on underwater sounds. There is so much that remains undiscovered there. It’s not silent – it never has been silent – and we make a lot of noise.”
Technological developments have transformed the depths at which researchers can record. But, as in the case of birdlife, Hans is driven jointly by curiosity to discover the unknown, and concern for the increasing damage done by people. He works closely with both conservation agencies, governmental ministries, and industrial partners, exploring the effects of the noise made by everything from seafloor exploration to CO2 storage activities and wind farm development.
His research is not all rainforests and ocean depths, however. The urban environment, and the interaction between the animal and man-made noises within it, forms an increasingly central component of his mission to promote interest in the natural world.
“We need to convince people that biodiversity is worthwhile to protect. I think that there is a big part of society that you could convince, but you need to tell the story in ways that they understand and they find interesting. But you will not draw them to forests or out of the city, so the urban biodiversity is, I think, critically important to actually have an overarching impact on the rest of biodiversity.”
With his students, Hans likes to lead what he terms a “silent walk”, on which phones and conversation are prohibited, and walkers are encouraged to listen fully to their surroundings. The audience at his Darwin College Lecture won’t be dragged from the Lady Mitchell Hall to the cold of a January evening, but Hans hopes nevertheless to encourage a similar shift in perception.
“I’ll try to make them really shape their ears, to listen for things, so that the next day when they go outside, or even that evening, they go outside as a different person acoustically, to make them more aware of the biodiversity around them.”
Join us for Hans’s lecture, Notes and Noises in Nature: Not a Swan Song? at 5.30pm on Friday 23rd January.
