Winter Moth Proves Able To Adjust To Climate Change

Since the climate pattern in winter and spring is changing, already for some 35 years, the winter moth hatched earlier and earlier. In warm years part of the caterpillars even appeared before the oak leaves did. Young oak leaves are the food source for this species’ caterpillars and without them they die within days. The winter moth reacted too sharply on climate change in the Netherlands.

Now it is found out that they are able to adjust to their new situation, so to their new climate. They did just that during the last ten years. NIOO ecologist Margriet van Asch explains: “At the same temperature eggs now hatch five to ten days later. The result is that they are again better synchronized with the oak leaves.”

Van Asch and colleagues researched the winter moth in nature and in climate rooms, under normal and under raised temperatures. This way, they can predict how these moths will adapt to the changing climate. “This change can not only be witnessed in our experiments, but also in the woods outside,” Van Asch reveals. “What makes them able to adjust, is the presence of sufficient genetic variation in ‘egg hatching moment’ within the moth population.”

The winter moth appears to cope with restricted climate change. This species adjusts quickly enough when compared to one of the moderate climate scenarios. “But we have to collect the same sort of information for other species and ecosystems,” argues project leader Marcel Visser. “Only then we can state by how many degrees the temperature may change without causing serious problems. This will give politicians something to base their target on, instead of that arbitrary 2 degrees Celsius warming.”

The winter moth Operophtera brumata lives in the woods. There they form a major food source for many songbirds like great tit and pied flycatcher. But these birds still have a problem. Their food source may be able to adjust and consequently survive in higher numbers, but they cannot. The caterpillars still peak earlier than their chicks and climate-induced asynchrony is still the reality for these birds.

This part of the winter moth project is funded by the Netherlands Organisation for Scientific Research. With this discovery Margriet van Asch of the Netherlands Institute of Ecology earned her doctoral degree.