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Meteorologists with wings

The bats determined: the air in Ayalon is much warmer than the air in Yarakon Park

A flying meteorologist in action. Tel Aviv bat. Photo: Tel Aviv University
A flying meteorologist in action. Tel Aviv bat. Photo: Tel Aviv University

A creative combination of forces between zoologists and geographers from Tel Aviv University led to a new study that uses bats to map the urban heat islands in Gush Dan. According to the findings collected in the field by the flying mammals, it turns out that during the winter months the air in Ayalon is up to 5 degrees warmer than the air in the Yarakon Park areas.

fly and map the heat islands in the city

The interdisciplinary research was conducted by a joint team of researchers from Tel Aviv University: Prof. Yossi Yuval and Dr. Aya Goldstein from the Bat Research Laboratory, School of Zoology, Purple School of Neuroscience and the Steinhardt Museum of Nature and Prof. Alexandra Chodonovski, Prof. Oded Potchater and architect Dr. Limor Shashua-Bar, the late From the Porter School for the Environment and the Earth. The results of the research were published in the journal Applied Geography.

"Urban heat islands are a well-known urban phenomenon. These are dense urban areas that are several degrees warmer than their surroundings, but for objective and environmental reasons, it is sometimes difficult to measure them. For example, it is almost impossible to place stationary measuring stations on every street, and sending mobile people with sensors also requires a large financial investment. In addition, measuring stations only measure near the ground, and do not measure temperature in three dimensions. One possible solution is the use of drones, but this solution is also problematic in terms of aviation permits to fly drones in urban areas, and after 20 minutes of flight they have to land and recharge again," explains Prof. Chodonovski.

In the current study, the team of researchers decided to take advantage of the added value of bats, which are considered to be excellent navigators and are also very well versed in urban areas. "Bats are much more successful pilots than drones," says Prof. Yuval. "They can fly 100 km in one night, and they are active at night when the heat island phenomenon is at its peak."

For the purpose of the experiment, the researchers attached tiny heat sensors to Egyptian fruit bats from an urban bat colony, and released them in downtown Tel Aviv. The clever bats had no trouble finding their way home, and on the way they mapped the air over different areas such as the city center, Ayalon lanes, Yarkon Park and Herzliya.

"Thanks to the bats, we were able to produce the first three-dimensional map of urban brown islands in Gush Dan"

A broad climatic picture in a short time

The experiment was conducted in winter, between eight in the evening and two in the morning, and among other things, the researchers discovered differences of between 2 and 5 degrees Celsius between dense urban areas and city parks. The researchers compared the data transmitted by the bats to four meteorological stations in Tel Aviv, and at the same time ran a large-scale field experiment of mobile meteorological stations to verify the data. In addition, they equipped people with similar devices and sent them to different parts of the city to make similar measurements.

Tel Aviv brown islands as mapped with the help of bats Photo: Tel Aviv University
Tel Aviv brown islands as mapped with the help of bats Photo: Tel Aviv University

"On the one hand, these are very light temperature sensors weighing 0.2 grams, so they are not as accurate as a heavy meteorological station. But on the other hand, their advantage is that they allowed us to get a broad climatic picture in a short time. From the analysis of the measurements it emerged that in the Ayalon area the measurements were very hot, compared to the Yarkon Park, where the air temperature drops and as soon as the bat crosses the Yarkon Park to Herzliya - the temperature rises again. Thanks to the bats, we were able to produce the first three-dimensional map of urban brown islands in Gush Dan."

Continue to use nature to explore

The researchers from Tel Aviv University call their original approach "Biology-Assisted Sampling" (Biology-Assisted Sampling), and according to Prof. Chodonovsky - they certainly do not intend to stop at bats: "We must use any mobile platform that can help us. Just as the bats helped us map urban heat islands, so pigeons can map urban air pollution without much effort, saving us a lot of money and many years of painstaking research."

"There is a lot of talk about smart cities and the 'Internet of Things,'" adds Prof. Yuval, "but there are many animals that already roam the city and it is possible to install tiny sensors on them that do not harm their behavior. For example, if we want to monitor pollution in the sewage system? Instead of operating expensive and complex machines, you can use the rats that hang around there all the time."

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