This year too, nature wakes up remarkably early, a phenomenon that has been noticeable for several years. Fifty years ago, the temperatures of the past few weeks would only have been recorded at the beginning of April.
Both animals and plants respond to these changing temperatures. If it freezes again after a warmer period, the plants will suffer frost damage. If it is dry early in the year, the population of certain animal species decreases. Due to the mild winters, the animals also wake up earlier from their hibernation. The toads already started their annual migration last weekend.
The most difficult thing is that the weather has become unpredictable, says Wim Veraghtert, scientific employee at Natuurpunt. “Toads do not cope well with the alternation of mild and cold weather.” In recent years he has noticed a negative trend: during mild winters, the toads wake up more often, burn more fat reserves and therefore start their migration in poorer condition.
Drought in summer, frost in late winter or early spring also have a negative effect. Veraghtert: “If the pools or ponds in which they lay their eggs dry up, the small toads die. This is also the case if the water they are in remains frozen for a long time.” If these phenomena occur a few years apart, this will lead to a decline in the toad population. “And then it will take a few years for it to recover.” This is also the case with tadpoles, which need a month in a pool before they can continue on their own.”
Spring also starts earlier for insects when temperatures are mild. Natuurpunt has already received reports of lemon butterflies and the peacock eyes. These species overwinter as adult butterflies in a hollow tree or under a loose piece of bark and are the first to appear in the spring. “At 15 degrees they wake up, whether it is sunny or wet,” says Veraghtert, “but if it is too cold, they crawl away again.” The butterflies then – just like the toads – use up part of their energy reserve.
Disturbed interaction
Not all plants or animals respond equally strongly to temperature changes, which can cause uneven shifts. “If it freezes soon, some trees and plants will stop blooming,” says Koen Es from the botanical garden in Meise. Animals that have already woken up from their hibernation can no longer find nectar or pollen and have to rely on their reserves.” This is especially important for bees. Last week Es already saw a few flying. “When it gets more than 13 degrees, the bee colonies are awake, both wild and farmed honey bees.”
Winter-flowering and early spring-flowering bulbs in particular are already in bloom, such as bulbous plants. The hazel trees have been blooming since the turn of the year. “Those trees are triggered by the temperature, they can withstand the freezing cold and do not need insects,” says Es. Snowdrops, hyacinths and witch hazels are also already in bloom, “but these are plants that we often plant in the garden ourselves.”
The alders have also bloomed in recent weeks, which is a month earlier than fifty years ago. People who are sensitive to alder and hazel pollen can suffer from hay fever in dry weather.
Whistling birds
In recent days, birds such as blackbirds and great tits could also be heard singing. “They also respond to the temperature,” says Veraghtert. “Those birds are flexible, they sing at mild temperatures, but do not yet build nests.” Birds are only vulnerable when they have eggs or young. “If the weather is bad in April, they will be able to raise fewer young.”
And then there are the migratory birds. “They come back earlier,” says Veraghtert. For example, the chiffchaff, which flies to the south of France, normally returns in mid-March, but now it is already the end of February. Some don’t even leave at all, but stay here.”
How nature will evolve depends on the weather of the coming months and years. If the weather remains mild, it will be a good year for the toads, the birds and the bees. “Only when mild and cold weather alternate year after year do we have a problem,” says Veraghtert. Because this fluctuation leads to a disturbed interaction between animals and plants, as a result of which the animals use up their reserves and therefore have less energy and ultimately less ability to reproduce.
