Drought has been raging for two years in the Pyrénées-Orientales. How to explain it?
In the Pyrénées-Orientales, over the last two years, only 500 mm of rain has fallen, levels that are found in semi-desert regions such as the city of Aman in Jordan. A drought is not only explained by a deficit of precipitation, there can also be a temperature that is too high which causes an excess of evapotranspiration, or even an ineffective quality of rain if it is torrential. In the Pyrénées-Orientales, in addition to the lack of precipitation, it is much warmer than usual with several days above 25° this winter. As a result, the vegetation is still active and consumes water.
But why isn't it raining?
For it to rain in the Pyrénées-Orientales, the rain must come from the Mediterranean Sea, that is to say from the south, but this has happened few times in the last two years. It is either a west wind that blows and the Pyrenees-Orientales massifs protect well from this type of wind, or a south wind, then blocked by the Pyrenees, this is what we call the effect of foehn. At the same time, some studies tend to show that, with climate change, the anticyclonic barrier tends to rise and dry out Spain and the Pyrenees-Orientales. All this will be confirmed in the years to come.
What to expect this summer?
The rain that may fall from now on will no longer be used to recharge the water tables; we will have to wait until next fall for that. The water table level, which is already very low, will therefore either stabilize or continue to fall. As for surface water
(rivers, lakes, reservoirs, etc., Editor's note)
, they will be just within standards if it rains and otherwise in deficit. So, at best the drought stabilizes, at worst it gets worse. For the moment, the majority scenario for the next three months is not based on excess water but on excess temperature.
Has the department reached a point of no return in terms of climate?
The Pyrénées-Orientales have always suffered droughts, the department is used to it. This means that the rain will eventually return... And periods of drought too. The difference is that there is now climate change coupled with all of this. These periods of natural variability which have always existed will now be more marked, as they are now. Climate change is gradual, it does not happen incrementally. So for the note of hope, yes the rain will return.
Concretely, will water restriction measures continue once this (long) period of drought has passed?
Yes, these restrictions will have to continue, or even be strengthened. We must continue to get used to these living conditions because the trend is towards drying out. Awareness is real in the Pyrénées-Orientales because now this drought is no longer seen only through “annoying” water restrictions but also through landscapes which are much browner. Beech trees in the Massane forest die back at 2% per year. Tree mortality is observed in the forests but also in the gardens and the streams no longer have water, the meadows are yellow... The desire of the departmental council to make the Pyrénées-Orientales an open-air laboratory for climate change is particularly interesting. The golf project in Villeneuve-de-la-Raho says that there is still a lot of work to be done in terms of tourism and water management.
How is tree mortality in the Massane forest national nature reserve a major indicator of climate change?
With a mortality rate of 2%, tree regeneration is much slower than their dieback. Observing this forest is extremely interesting because for at least 14,000 years it has been very little exploited by humans. She suffered cold and then hot periods, but this time, the warming was the most rapid in her entire life. It is also one of the southernmost beech forests in Europe.
You insist on the need to anticipate. How does this translate into agriculture?
From 2050, it will no longer be possible to grow apricots in the plains of the Pyrénées-Orientales not for lack of water but because there will no longer be a sufficient number of hours below 7° C during winter (between 400 and 600 hours) to allow the tree to flower and then produce fruit. The challenge for the Pyrénées-Orientales department is to overhaul its agriculture with a new production sector. This will take several decades. As far as vines are concerned, we must now look at grape varieties that are planted further south, in Andalusia or Morocco for example. Of course, the wine will not be the same because the terroir and the soil are different, but the plant will be more adapted. In terms of drought resistance, the olive tree can compete with the vine. Prickly pear, which is a cactus, carob, can be alternatives. Pistachio will also be interesting, as well as pomegranate. If there is water, avocado and mangoes can be considered, as can persimmons and citrus fruits which must be planted protected from frost. In short, we need to start thinking about it now.