Woodlice that live in rural areas are more resistant to drought and flooding than their urban counterparts. This is according to new research by ecologists at Vrije Universiteit Amsterdam and Aarhus University on the woodlouse species Philoscia muscorum.
The results are striking, because it was actually expected that animals in cities would have adapted better to these stressful conditions. The research- published in Pedobiologia - shows that urbanization does not automatically make animals more resilient to the effects of drought and extreme rainfall.
Cities pose significant challenges for animals. Temperatures there are often higher, while roads, sidewalks, and other paved surfaces prevent rainwater from seeping into the soil as easily. As a result, dry conditions and flooding can alternate.
VU ecologist Wouter van der Vegt: “We wanted to know whether woodlice living in cities have adapted to these conditions. So we compared woodlice from urban and rural areas and investigated in the laboratory how well the animals could withstand dehydration and submersion in water.”
Rural woodlice are more resilient
The results were contrary to expectations. Woodlice from urban areas turned out to be not more, but actually less resistant to both dehydration and flooding than their rural counterparts. Rural populations also responded better to prior exposure to drought. This suggests that they are better able to adapt their physiological response to changing conditions.
Among rural woodlice, the researchers also found a link between the ability to withstand drought and flooding. Animals that were more resistant to drought were generally also more resistant to submersion. This so-called cross-tolerance may mean that mechanisms that protect animals from one form of stress also come in handy against another.
It was also striking that it wasn’t just the severity of drought that played a role. Prolonged exposure to mild dehydration led to higher mortality rates than a shorter period of more severe dehydration. How long animals are exposed to stress can therefore be at least as important as how intense that stress is.
Urban Nature Under Increasing Pressure
These findings are relevant as cities increasingly face high temperatures, drought, and heavy rainfall. The results show that animals that have lived in the city for a long time are not automatically better able to withstand such extremes.
This is important for understanding and protecting biodiversity in cities. Woodlice are small animals, but they play a key role in ecosystems by breaking down dead plant material and thus contributing to the nutrient cycle.
The research also shows that different forms of environmental stress cannot be viewed in isolation. An animal may react differently to a combination or sequence of drought and flooding than to a single stressor on its own.
“Our results thus underscore that climate-resilient cities must not be viewed solely from the perspective of humans. To protect urban biodiversity, we also need knowledge about how animals respond to the combination of heat, drought, urban paving, and extreme precipitation,” says Jacintha Ellers, professor of Evolutionary Ecology, summarizing the research.