Spain's almond trees bloom a month earlier due to climate change

The almond trees in southern Spain are covered in white flowers almost a month earlier than usual. Temperatures in Spain this winter have been warmer than average for this winter, averaging 10°C on December, 2°C above the norm between 1981 and 2010.

Spain almond trees bloom

In popular parlance, the expression “the almond tree is in bloom and the weather is nice” predicts warm temperatures that favour fruit germination once the petals have fallen. However, climate change causes abnormal days of 20°C in winter and dangerous temperature drops in the first weeks of spring. 

The joy is as fleeting as the event itself, giving way to fear of late rains, cold and snow which can completely ruin the harvest.

José Egea a scientist from the Center for Soil Science and Applied Biology of Segura, CSIC Fruit Improvement Department, explained that flowering depends on each year, but he admitted that lately there have been continuously higher temperatures than normal both in summer as in winter, although what matters for these species, especially from October.

Spain is the world's second-largest producer of almonds (after the US) and one of the largest exporters of the seed. Therefore, a bad harvest can have serious economic implications, explains Enrique Salvo Tierra, professor of Botany at the University of Malaga.

What is Phenology?

Phenology is the science that studies biological events in the animal and plant world such as leaf development and plant flowers in spring, fruit ripening and leaf fall in autumn, and breeding behaviour and migration of animals among other aspects.

In the last decades, when some climatic factor is altered as a consequence of global warming, for example, temperature parameters, fauna and flora species can register alterations in their natural calendars.

Thus, this year in Extremadura, the cherry trees have accumulated some 600 hours of cold, amounts that are below the average for other campaigns and that, for the moment, are deficient to achieve optimum flowering and regular.

In phenology, flowering and pollination is determinants, but they are not unique parameters, because it is also interesting how cold hours affect them, which in the case of cherry trees is equivalent to an average of between 800 and 900 cold hours -between 0 and 7 degrees- for the correct preparation of the flowering.

Climate change

Regarding the relationship between the advancement of the almond process and climate change, José Egea pointed out that although he personally thought that the process was going to be more progressive, experts are observing how the climate and flowering are changing and that the temperature is increasing.

"It is going much faster than we thought but there are not enough years to know with absolute certainty that this is the case. However, there is evidence that we are in that change and that it is much faster than a natural warming process," which has value.

Finally, he estimates that in general terms the blooms that need less cold are those that are coming forward year after year and those that need a lot of colds, however, are being delayed.

It is not the first time that this type of imbalance has been observed in nature. In fact, with the advance of the climate crisis, these "anomalies" are being detected with increasing frequency in various corners of the globe. 

Droughts key trigger for this phenomenon

The 'Climate Connections' platform of Yale University reports similar cases in the United States. Experts point out that droughts could be a key trigger for this phenomenon. At a time when high autumn temperatures coincide with a lack of water resources, plants could be forced to flower out of season.

Several studies suggest that, on the one hand, the vegetation is flowering out of season and, on the other, that the flower season is coming earlier. 

A study from the University of Cambridge suggests that in the United Kingdom outbreaks have been brought forward by up to a month in the last century. According to the experts who have led this analysis, this alteration of the natural calendar could have consequences for the entire ecosystem. Especially for species (or activities) that directly depend on blooms.

Experts point to two main dangers behind this phenomenon. For one, fall blooms could reduce the number of buds available for spring. And on the other hand, the early spring shoots could be exposed to more climatic disturbances. "If fruit trees, for example, flower early after a mild winter, entire crops can die if the blossoms are hit by a late frost," the Cambridge analysis highlights.

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