Climate change threatens nature: spring is coming sooner than expected!

Climate change threatens nature: spring is coming sooner than expected!

On April 8, 2025, the attention of German researchers is once again drawn to the changes in nature caused by climate change. In particular, the phenological clock, a tool for graphically representing vegetation phases, plays a central role in the analysis of these developments. According to the KU The phenological clock shows ten periods instead of the traditional four seasons, providing a more detailed insight into climate-related changes.

The phenological clock is updated weekly, with the outer ring showing the long-term progression of the phenological seasons, while the inner ring represents the current status. This is particularly helpful for documenting the sensitive reactions of early flowering plants to rising temperatures. Such phenological information is valuable for allergy sufferers who can better assess pollen levels and for farmers who want to plan their sowing and fertilization accordingly.

Early bloomers and their importance

Careful observation of plants is crucial because the timing of flower entry is strongly linked to food availability for insects, particularly nectar-feeding species. Flowering phases that are too early can therefore have negative effects on the ecological balance. The German Weather Service (DWD) has an extensive database that goes back to the 19th century, supported by over 1,100 volunteer reporters. They document the development of plants and report on leading phases, such as the hazel blossom, which signals early spring.

The phenological seasons are characterized by specific plant events such as flowering and fruit ripening. Analysis of the data shows that early spring has started noticeably earlier in recent decades. Between 1961 and 1990, early spring started on average on March 3rd, while in the period from 1991 to 2020 it started on February 14th. This can be directly linked to rising temperatures.

International Phenological Gardens

Another important instrument for monitoring phenological changes is the network of International Phenological Gardens (IPG), which was founded in 1957. The IPG now has 171 stations in 18 countries, including one in the USA. The network enables the comparison of phenological data and the targeted analysis of the effects of climate change on plants. Like from the Weather Service reported, the plants in the IPG gardens are genetically identical and come from a single garden in Fürstenfeldbruck. Differences in phenological observations are therefore due to climatic conditions and not to genetic differences.

The specific data treasures collected here include the observations from the IPG site in Eichstätt. This data is processed and analyzed by KU researchers after the current growing season. Susanne Jochner-Oette took over the coordination of the IPG in 2023, which will further strengthen efforts towards systematic data collection.