Climate in the Czech Republic

2018 was just one in a series of extremely hot and dry years. The average annual air temperature across the country—9.6°C— was 1.7°C above the 1981 to 2010 avarage. Annual rainfall in the Czech Republic in 2018—522 mm—was only 76 percent of the 1981 to 2010 avarage. As it had already been unseasonably dry for several consecutive years, the conditions in 2018 exacerbated the already low water levels in the landscape, streams, and groundwater, making the signs of drought all the more pronounced.

In places such as Zruč nad Sázavou, 2018 brought extreme drought conditions. In August 2018, the daily flows of the Sázava River fell well below average—up to one quarter the flow of previous years— making the riverbed visible in some areas. Such consequences affect not only boaters, when the flow of any river is reduced so dramatically, several parallel processes occur: shallow and slow-flowing or standing water is thermally unstable and warms up more easily (the Sázava, for instance, was over 20° in the summer months) but cools down just as quickly at night. The oxygen content of the water is similarly unstable.

Warm and shallow water also evaporates more quickly, while low-flow streams change the ratio of river water between the water that flows into it from sewage treatment plants. (there were at least 60 sewage treatment plants in the Czech Republic in a year that discharged more than 50% of the water in the stream, some even more than 80%!). Wastewater treated in accordance with national legislation improves waterflow, but when it makes up such a high proportion of a stream, it seriously reduces water quality. The concentration of phosphorus and other pollutants increases, leading to significant increases in phytoplankton.

The quality of the water in streams deteriorates, and the native plants and animals are impacted by the changes to their habitats. Other organisms within the ecosystem are also threatened. Hydrological drought is not just about “not enough water”, but poses a comprehensive threat to the viability of the entire river ecosystem. In Zruč nad Sázavou, for instance, the water turned completely green in August 2018, due to an overgrowth of cyanobacteria, green algae, and diatoms. The water was not suitable for any type of recreation, and the ecosystem in and around it was devastated. And while the Sázava is not a source of drinking water, the very same mechanisms are at work in the streams that supply Czech reservoirs with drinking water.

Mr. Matoušek is a winemaker from a small village in the south of Moravia. He has been making  wine for over thirty years, and he started a small company which he has always dreamed of passing on to his daughter, who graduated from the Valtice wine school. But in the last five years, he has slowly abandoned his dream. Why?

The grapevine is an extremely resilient plant that thrives even in relatively severe drought and high temperatures, as its long roots enable the plant to get water from several metres under ground. This, however, applies only to older plants; new seedlings are sensitive to drought. For the last five years, Mr. Matoušek’s new seedlings have required several years of manual watering. Without it, they would not have survived the hot, dry summers at all, or their growth would have slowed down considerably and, most importantly, they would have borne little or no fruit. A grapevine with no grapes is useless to a winemaker, so Mr. Matoušek, who cannot afford to install an irrigation system, waters the plants by hand and tries in various ways to prevent soil erosion.

Even well-established vines are affected by droughts. Although plant does not usually dry out, but a lack of water causes stress, which, in turn, leads to smaller harvests. Furthermore, hot and sunny weather also affects the quality of the grapes – Mr. Matoušek says the sun "bakes" them, and you can't make good wine from "baked" grapes.

White wines in particular are becoming increasingly difficult to make in South Moravia as the temperature rises and other climatic extremes affect the development of sugars, acids, and aromatics in the grapes. The harvest also begins days or weeks earlier than in the past, and therefore often takes place at higher temperatures. Sun-warmed grapes cannot be processed right away, as this would adversely affect the taste of the wine, so the grapes are often artificially cooled in cellars, or they have to be harvested at night or early in the morning. Climate change is also bringing new diseases and pests, such as ESCA, a new, incurable fungal disease, which is spreading in the Czech Republic due to alternating periods of drought and heat and long periods of rain.

Even if Mr. Matoušek manages to keep his seedlings alive, protects the vines from diseases and pests, and buys a chiller or dry ice to protect the grapes, he could easily lose a large part of his crop to spring frosts. Of course, frosts have always troubled winegrowers, but they have become more damaging in recent years. Grapevines come to life earlier after the winter, thanks to higher average temperatures, and then spring frosts, which have become more frequent due to climate change, affect them at a more advanced stage of the growing season. Simply put, grapevines come up earlier, and then freeze even more when the frost comes.

One apparent solution would be to switch to grape varieties that are more resistant to heat and drought, as well as to diseases and pests. But how should Mr. Matoušek decide which varieties to plant now, when most of them will bear fruit in fifteen to twenty years, and no one knows what the climate will actually be like in South Moravia at that time? Should he clear out vineyards that are still fertile and replace them with other varieties, or wait another 10 to 15 years and then try to estimate which varieties will thrive in another 25 years? And how can he defend himself against the spring frosts that, according to climate models, will always affect this landscape and will therefore regularly threaten his vineyard?

To be a successful vintner, Mr. Matoušek should plan for the long term, however, he lacks knowledge of the basic variables that would enable him to plan. And thus he has abandoned his dream of handing over the family business to his daughter. He assumes that in thirty years, growing grapes in his home village will be such a complex and expensive business that his daughter will not even want to do it. Fortunately, he still retains his sense of his humour: “I'll buy a plot of land near Trutnov [a town in the far north of the country, near the Krkonoš mountains],” he says, “and we'll start growing grapes there!”

If you're lucky, you'll find a creature in the Czech rivers that has lived through the time when the Czech lands were a kingdom. It is also one of the last individuals of its species still surviving in Czech waters. The river pearl mussel is one of the oldest living creatures in the Czech Republic, and, much like approximately one third of the plants and animals in the Czech Republic, it is threatened with complete extinction.

The pearl mussel can live for up to 150 years, but it is extremely sensitive to the quality of its environment. While 150 years ago there were hundreds of thousands of these mollusks in Czech waters, mainly in the middle reaches of the Vltava, Otava, Elbe, Odra, and Blanica basins, today they are far more rare. Urbanisation, transport, agriculture, and other interventions in the landscape have made it difficult for pearl mussels to find optimal conditions for reproduction and survival in the Czech Republic.

To reproduce, pearl mussels need a host. At the end of the summer, the females release their larvae—known as glochidia—into the water, and let them drift freely until they find a fish, usually salmon, in whose gills they will settle until the following spring. But the path of the salmon, which used to swim hundreds of kilometres from the sea to the Czech rivers every year, has been blocked by weirs and locks. The larvae have thus found a new host over the last 100 years: the brown trout. However, even these fish can’t get far without fish ladders to help them cross weirs, dams, and hydroelectric power stations.

In addition, young pearl mussels need a network of rivers and streams where the water does not drop below 15 degrees in summer. The water must be also be as clean as possible, roughly within the parameters of drinking water for humans. The inorganic calcium that enters the water from sources such as concrete rubble, pollution from intensive farming, and chemical waste, as well as a loss of shade trees and bushes to cool the water are all problems for pearl mussels. Naturalists refer to pearl mussels as an umbrella species; when they thrive, so do the animals and plants near them. But water that would suit young pearl mussels is virtually non-existent in our region, so only older mussels can survive.

All of this means that saving the pearl mussels is not easy. Conservationists transplant the small larvae directly into the gills of a trout, help the trout survive in tubs and riffles, feed the young mussels, and plant them in riverbeds. Whether the next generation of these larvae can grow up will depend on our treatment of the environment.