It stayed warm for a long time in autumn and after turning into the warmest year ever, it already feels like spring in January. It confuses nature: hazelnut trees, alders and daffodils are already in bloom, and frogs and salamanders awaken early from hibernation. A month and a half into winter, there is now above all the hope that the temperature will take a step back, without the frost returning.
It’s a confusing winter. Many Dutch people were skating in mid-December, including the Wageningen biologist Arnold van Vliet. But he also noticed something on the ice, he tells NU.nl: in some places you couldn’t skate because the ice was full of oak leaves.
This is not due to the exceptionally mild winter, but to the autumn that preceded it: September, October and November were warmer than ‘normal’ for three consecutive months. As a result, the leaves stayed on the trees much longer – sometimes up to and including the onset of December frosts.
The warm fall also led to early ripening of hazel and alder flowers, according to Van Vliet. He saw both species of trees bloom around Christmas, about a month and a half in advance. This also means, as soon as it dries up, that the first hay fever complaints can already occur in winter, especially if the birch pollen starts mixing soon.
The short frost in December was a reset button for nature
It’s possible that the brief frosty spell also hastened nature’s awakening, says Van Vliet. Many species need a cold period for the seeds to germinate or to resume their growth process. For example, after that first winter chill, sap flow in trees may start sooner.
This is not without risk. We only had one week out of the two coldest winter months. For example, if severe frosts occur again in February, the branches of trees that have gone into the spring position will freeze and die. This is not only a problem for nature, but also for fruit growers, for example. “Frozen flowers are a crop, but dead branches are years of damage,” says Van Vliet.
So it’s actually to be hoped that winter doesn’t really come back when spring comes early. In addition, it is important that species that depend on each other go hand in hand. This sometimes goes wrong. Some plants and animals wake up due to rising temperatures, others more due to increased light, when the sun rises higher in the sky again.
African migratory birds don’t know that our spring is coming
Yet other animals have no idea how hot it is (already) in the Netherlands. An example of this is migratory birds that spend the winter in Africa and return “too late” due to the rapid warming of the European spring.
This has been studied, for example, for the piebald flycatcher. He has to find a mate here, build a nest, hatch the eggs and then find (a lot of) food for the chicks. In early spring, the flycatcher has the most difficulty with this – the peak of the food supply has already passed, when the young finally arrive.
Back to the here and now. Van Vliet already saw the daffodils in bloom on Friday. They are actually waiting for bumblebees to pollinate them. But if those bumblebees wake up too, the further supply of nectar and pollen is still too small and there’s a good chance they won’t survive.
Frogs and salamanders have an empty tank faster
For example, there are also reports of brown frogs and small newts that have again been observed crawling and hopping, while they should still be hibernating. Their problem is not only that they find little food, but also that they burn up their limited energy reserves faster in hot weather. “This also applies to species that hibernate,” says Van Vliet.
Looking at the KNMI’s fourteen-day weather forecast, it remains milder than the average for the moment (over the past thirty years). Starting next week, temperatures will be closer to normal. If it stays like this until March, it would be the best for nature. But above all no real return from the winter cold.
