Copper forests. The autumn colours in the Genal Valley attract thousands of people at weekends who want to walk among the chestnut trees. / ÑITO SALAS

Copper forests. The autumn colours in the Genal Valley attract thousands of people at weekends who want to walk among the chestnut trees. / ÑITO SALAS

The colours of autumn come later

Climate. Global warming means autumn starts about 20 days later than before and is shorter, affecting trees' colour change

IGNACIO LILLO

Chromatic change has arrived late in Malaga province this year. Summer continued practically all the way through the month of October, with warm temperatures and hardly any rain. Global warming has meant that autumn is beginning about 20 days late on average, according to figures from Malaga University (UMA), where the data for the past 50 years has been analysed.

A shorter season affects trees in general, but chestnuts in particular; this in turn reduces the natural spectacle known as the 'copper forests', which attracts thousands of people to the Genal Valley to admire the palette of colours that nature paints on the countryside at this time of year.

"What we are seeing is that the summer period is getting longer and the intermediate seasons, spring and autumn, are getting shorter," said Enrique Salvo, who is a botanist, professor of Environmental Sciences and director of the chairs for Nature Conservation at the International University of Andalucía (UNIA) and the FYM-Climate Change (UMA).

At the autumn equinox (22 September) there should be a drop in temperatures and that is when rain is expected, which in the case of Malaga province normally comes from Atlantic squalls.

"But this has been getting shorter and shorter and has led to this new intermediary season that we call 'veroño' [a cross between 'verano', summer in Spanish, and 'otoño', autumn], with higher temperatures than normal and lasting longer, combined with an absence of rain," he said. Winter is also shorter and is being reduced in favour of a longer and drier summer.

Biological clock

"This is why the changes in the colour of the trees which we used to enjoy so much throughout October and November now last for a shorter time, and within a few weeks they are followed by a cold winter, which causes everything to change in the plant world," said Salvo.

Broadly speaking, plants have two ways in which to act: some adapt better to the biological clock set by daily hours of sunshine, and this influences the production and fall of the leaves and change of colour. Deciduous trees like the chestnuts are among those that suffer most, because they are used to this clock that is now out of sync with environmental variables.

The other reaction is that of almond trees, which need a certain number of hours of cold to activate the mechanisms to work below the ground, with more root growth to absorb the rain they require in order to blossom in spring. Let's say they accumulate in the autumn and in the winter they become dormant before the spring equinox.

"All this is linked, so if the first part fails and there isn't enough rain in autumn, then spring comes earlier and is poorer, which creates a disturbance," says Salvo. Therefore the chromatic contrast will be increasingly greater, because some plants will be more dependent on the biological clock and others affected by the lack of hours of cold weather.

In Malaga province this can be seen directly from the almond blossom, which is occurring earlier and earlier in January when it used to be February. This is also something that catches the pollinating insects off guard, because they will not be active at the same time as the flowers open.

As a botanist, Enrique Salvo predicts that with the copper forests of the Genal and their transition from green to yellow, orange and red before the leaves fall, "this wonderful chromatic range" will become more homogeneous and will change more rapidly. In short, it will become less beautiful and less of an attraction, and all due to climate change.