Davide: introduce yourself…
My name is Davide Dominoni, a postdoctoral researcher affiliated with the Netherlands Institute of Ecology in Wageningen, the Netherlands, and the University of Glasgow in Scotland. My background is in Natural Sciences and Conservation Biology. After my Master’s degree at the University of Parma, Italy, I left my home country and worked as research and field assistant in Ireland and Australia before moving to Germany to start my PhD.
How did you get involved in light pollution studies?
It started with my PhD in Germany. I was always interested in anthropogenic impacts on wildlife, and I knew I wanted to do a PhD related to urban ecology. When I saw the job offer for a PhD on the eco-physiological effects of light pollution in the European blackbird, I thought it would have been an excellent opportunity to develop my interests.
Could you tell us a little about the scope of your research, and your most relevant findings to date?
My research integrates two main concepts. First, light is the most potent environmental factor that regulates the rhythms of life, because it signals when is the right time to be awake, to forage or to sleep, and it also indicates daylength, thus whether it is summer or winter, for instance. Light has therefore profound effects on the behaviour and physiology of virtually all organisms. Examples are daily rhythms of singing behaviour of birds or the up and down movement of leaves on plants, and the migration of millions of animals that happens at specific times of the year. Second, because organisms have adapted to these natural light/dark cycles, they have developed physiological and molecular mechanisms to synchronise to such cycles and even anticipate them. My research started from a simple hypothesis: if organisms tune their behaviour and physiology to natural light/dark cycles, then light pollution should affect such processes because it can disrupt such cycles.
In order to test this hypothesis, I first had to demonstrate that wild animals are exposed to light pollution in the first place. This is not trivial: animals move and can easily seek and hide in dark places to avoid light. To this scope I used tiny light loggers are deployed them on wild European blackbirds that were breeding in the city of Munich, in Germany, and in a nearby dark forest. Birds in the city were exposed to much higher light at night than the forest cousins, but the light intensity was still quite low if compared to the brightness of street lamps. Thus, the next question was whether such relatively low levels of light could impact the blackbirds behaviour and physiology. To answer this I brought city and forest birds to the laboratory and exposed to the same levels of light at night that I recorded in the field, to rule out any other confounding variables that may co-vary with light in the city, such as noise and temperature. What I found was impressive: birds exposed to light levels 20 times lower than the intensity of a typical street lamp bred 1 month earlier and show twice as much nocturnal activity than birds exposed to a dark, forest-like night.
Although these results were strong and intriguing, at the end of the PhD I was left with an important question: is light pollution bad, good, or neutral for birds? To solve this dilemma I had to integrate different approaches from different fields of research.
First, I used molecular techniques to understand what biochemical pathways were altered by light pollution, and what we know about such pathways. I found strong effects on pathways related to stress and cognitive function, suggesting that light pollution has to power to fundamentally altered processes that are now to be link to survival and reproductive success. Second, I went back to the field to understand what the long-term effects of light pollution are on the fitness of wild birds. This is an ongoing, 7-year project that is a part of a large initiative called “Light on Nature”. It is a Dutch project were street lamps of different colours are mounted in several different forests across the Netherlands. My own research looks at long-term physiological changes in the songbird Great tit. This species breeds in nest-boxes, which makes it ideal to recapture the same bird several times to obtain physiological samples, but also to look at age-related changes in reproductive success and survival, what we called “senescence”. I hope that this will better inform both science and policy-makers about the long-term effects of light pollution, as well as indicate what type of light colour might mitigate such effects, which is a very important issue as the current trend is to replace the old Tungsten lamps with LED lights.
To what extent your findings on birds may help to understand effects on humans?
My research has profound implications for human health too, as we are becoming more and more a 24-h society where we are constantly exposed to light. This is known to be a problem for human health, but studies on humans are mostly correlative, and the use of laboratory models such as mice and rats can only partially solve the problems because they are nocturnal animals. Birds are diurnal and warm-blooded, like us, they live in cities and show strong responses to light pollution. Plus, it is relatively easy to study them both in the wild and in the lab, making it easy to obtain several samples from the same animal or to follow it for its entire life, which is helpful if we want to really grasp the long-term effects of light pollution.