Beech forests across Catalonia, including the Montseny massif and Alt Berguedà, have turned green significantly earlier than usual this year, with leaves emerging around 10 April in lower areas. This premature leafing is likely due to the high temperatures experienced during April, according to the source.
The early emergence of leaves, observed across various altitudes, poses a significant risk to the beech trees (Fagus sylvatica), which are typically late-budding species. New shoots are highly sensitive to sub-zero temperatures. While dormant winter buds can withstand intense frosts of -20 or -30 degrees Celsius, the tender new shoots can barely tolerate slightly negative temperatures. A drop of just a few degrees below zero can cause severe damage to the new leaves and stems, often resulting in them being “burnt” and dying. If this occurs, the tree is forced to attempt to re-sprout, which is not always feasible. This re-sprouting effort demands a considerable amount of energy from the tree, weakening it and making it more susceptible to diseases or, in the worst-case scenario, leading to its death.
In the Alt Berguedà's Catllaràs massif, leaf emergence this year occurred a week earlier than last year and 10 days earlier than in 2022, according to Marc Noguera, a phenological observer for Meteocat (the Catalan Meteorological Service). Data from Meteocat indicates that over 50% of new leaves appeared between 18-20 April this year, compared to 25-27 April in 2025, 27-29 April in 2024, 21-24 April in 2023, 28-30 April in 2022, 26-29 April in 2021, and 28 April-1 May in 2020.
Beech Tree Distribution in Catalonia
Beech trees are characteristic of humid regions at mid-latitudes and are common in humid Catalonia, particularly at mid to high altitudes (above 800-1,000 metres) in areas like the Montseny massif. They are also prevalent in the Vall d'Aran and the northern slopes of the Pyrenees. On the southern side of the Pyrenees, they are found in Garrotxa, Alt Empordà (in Les Alberes), Ripollès, parts of Osona, and Alt Berguedà. More isolated occurrences are noted in Alta Ribagorça, Pallars Jussà, Solsonès, and Moianès. Notably, the small beech forests in the Ports de Tortosa massif, in the country's southern extreme, are considered the most southerly in Europe. The Fageda d'en Jordà in Garrotxa is an exception, growing at just over 400 metres.
Monitoring Climate Change Impacts
The timing of leaf emergence and fall is a type of phenological information, similar to the arrival of swallows, that recurs annually and varies based on several factors, notably meteorology. Observing and documenting these events year after year provides crucial data on how climate change is altering the rhythms of plants and animals. Since 2013, the Catalan Meteorological Service (Meteocat) has operated the Catalan Phenological Network (Fenocat), a programme that collects systematic observations from 50 volunteer participants. These volunteers diligently record the different phenological states of 25 plant species, 14 bird species, and six butterfly species. Additionally, the CREAF ecological research centre develops the 'Nature's Rhythm' project, which gathers phenological information contributed by any citizen, further expanding the dataset for scientific analysis.
The ongoing scientific monitoring of these changes is of high importance, as the altered rhythm of beech forests serves as a clear indicator of climate change's impact on Catalonia's natural environment. Continued observations will be essential for understanding and potentially mitigating the long-term effects on these vulnerable ecosystems.
