First of all, it must be said that aphid overpopulation in forests is nothing new or unusual. It occurs regularly about every 10 years. This is related to the reproductive cycle of the woodcock. In most cases, however, the consequences are not as devastating. Why did this happen this year?

typický smrkový les

First, we need to understand that spruce bark beetles primarily (and surprisingly) nest in spruce trees. But nature, of course, gives trees the ability to defend themselves. The tree\’s ability to defend itself against the woodlouse simply depends on the location of its natural habitat. Like most insects, woodlice do not like low temperatures very much. Trees, on the other hand, prefer cold. This usually prevents the auklets from reproducing quite effectively. The yellow warbler has only a few individuals that grow at lower elevations. Enough to survive, but too few to reproduce.

However, humans have intervened in this natural relationship. This type of wood has so many advantages. First, it has a very wide range of uses. In addition, this tree grows so fast that the money invested in its cultivation is quickly recovered compared to other species. It is therefore not surprising that it has become widely cultivated in the country.

oblast zničená kůrovcem

In fact, the Czech Republic does not have ideal conditions for growing this species. Our region is mostly lowland, and the only natural occurrences are on the mountain ridges at the border. Because of the suboptimal conditions, the trees are susceptible to a variety of diseases and parasites (including chytrid beetles). They are also nearly monocultures, which means that they do not have to travel far in search of food (thus making them ideal prey for a variety of insectivores). Nevertheless, spruce has been grown this way for decades. There have been mishaps caused by the yellow beetle, but never as devastating as this. So why this year?

There are several reasons here. First, the climate is warming. This weakens trees that prefer the cold, but is ideal for the woodlice. In addition, recent years have seen little rainfall and long dry summers. Of course, this is also not ideal for trees. Especially if their natural habitat is in the mountains, where rainfall is high all year round. Another cause is the decline in natural enemies of insectivorous birds and woodlice. We can all agree that the number of songbirds is declining, especially in fields and forests.

So what is the solution? Drastically reduce the percentage of spruce cultivation and concentrate on more suitable tree species. It is also necessary to stop managing forests through monocultures and to bring the ratio of different tree species to near equilibrium. The calamity has cleared the forests. From this perspective, that is a good thing. It is a good thing from this perspective, because it has freed us from our ecological burdens and given us a chance to make a fresh start. The question is whether we will seize this opportunity.


— 9 October 2022