Unprecedentedly late summer increases pressure on forests
Never since records began have there been so many summer temperatures before June 10
BarcelonaSummer has started extraordinarily early this year. Different indicators reveal that for some weeks now we have been living in full summer temperatures, even though we have not even reached June 15 yet. ARA has used details from all 87 Meteocat stations, and adding up the number of days each reached at least 30ºC, we saw this had happened 658 times before June 10. This figure alone means nothing, but in comparison with previous years it shows how exceptional this is. On average, at this time of year there are 30ºC has been reached 122 times. In 2022 the figure is almost double the previous record, which was 2015.
Open data from Meteocat do not allow us to calculate for the years prior to 2009 for the whole of Catalonia, but individual series such as Lleida make it clear that a summer as early as this year's is unprecedented. In Lleida, up to June 10, there have been 27 days registering temperatures above 30ºC. Since records began in 1960, the highest number had been in 2015, when there were 19.
It is no longer a question of specific episodes, but of a continuous anomaly. In the last 30 days, Catalonia has been on average 4 °C warmer than usual. This means that every day for a month there have been temperatures 4 degrees above what would be expected. Since 2009 there is no precedent at any time of the year for such an anomalous situation like this. The period of highest sustained high temperatures in recent years had so far been in February 2020, when this anomaly reached 3.2 degrees. And one last fact, taking as a reference the period 2009-2020: this year we have already had 22 noons with temperatures one would expect in summer. That's three whole weeks with summer temperatures at midday before June 15.
And now we expect a heat wave to hit. This Sunday was the hottest of the year so far in Catalonia and temperatures will stay very high at least until Friday. The worst of the heat is expected between Wednesday and Friday, with temperatures in Ponent reaching 40ºC. On the coast at night it will not drop below 25 degrees at some points and at midday the felt temperature will be around 35ºC. This is extreme heat before June 15. When and how this heat wave will end is still unknown. A scenario in which the temperature plummets at the start of next weekend is not out of the question, but the forecast is still uncertain.
Forests under pressure
There is no doubt that a longer summer is making life more difficult for trees. More temperature means more evaporation and, therefore, more need for water. In addition, the precipitation data of the last 12 months place us in a context in which large regions of Catalonia are in moderate or severe drought, according to Meteocat's calculations. In regions such as Alt Urgell, Pallars Jussà, Solsonès, La Selva, Vallès Oriental and Osona there are sectors in which the drought during the last 12 months is very severe.
Annual DeBoscCat report is a joint project by CREAF and Forest Rangers which verifies on the ground the state of the forests in Catalonia. The last report, with data collected after the summer of 2021, certified that the area of forest in decline –that is, in danger of dying due to drought– had doubled compared to the previous year. The new area affected by drought in 2021 was 3,600 hectares, a relatively small area compared to recent dry years, such as 2016, 2017 or especially 2012, but CREAF and Agents Rurals found that more than 12,000 ha that were already in drought from previous years had worsened their situation.
According to CREAF research technician Mireia Banqué, it is difficult to predict what state the forests will be in when the next report is launched in September, since, despite the summer being very hot, much will depend on the possible showers. According to Banqué, in recent years we have been observing the resilience of trees, which limit their growth in order to survive, but it is uncertain at what point the forests may reach their limit.
What does seem clear is that increasingly higher temperatures will make life more difficult for species such as Scots pine and beech, which may be progressively replaced by more resistant species such as oak, holm oak or Aleppo pine. This change has already begun in recent years, Banqué explains.
The area of forest in Catalonia has gone from 28% to 35% in the last twenty years, mainly due to agricultural lands being abandoned. This is bad news, since the resources of the forests to survive are increasingly limited and the fact that the surface area is increasing only causes competition for these resources. According to Banqué, we have to lose fear of admitting that we have to cut down trees and reduce forest mass to improve trees' quality of life and make them healthier.
At this point, the drought is more about the land than water reserves. The reservoirs of Catalonia's internal basins remain at 58%, a fairly good figure given the situation. Among the emptiest, Llosa del Cavall (at around 40% of capacity) and Siurana (close to 30%) stand out.
