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2021: an exceptionally dry year or the new normal ?

2021 (so far) is one of the driest years ever recorded in the northeast of Corsica (plaine orientale + Castagniccia + Cap Corse). In Campile, we have had about 6 days of significant rain since the beginning of the year… We’ve had some rain in winter and spring but far less than normal (about 1/3% less). I made an overview of the recorded rain in Bastia (which is not equivalent to Campile but the closest open-data weather station).

June-August: 35% less than normal (Bastia), and 94% less than normal in Ajaccio! (3 mm in 3 months…)


From June onwards, we have had virtually no rain for 3 months except one big thunderstorm (+-37 mm at the end of August). In September we had virtually no rain (only 4 mm of rain (95% deficit) recorded in Bastia and Ajaccio...) ) and in October we have had about 71% less than usual (data from Bastia )

Therefore, over the first 10 months of the year we have an average deficit of 44%... Assuming that we have a similar deficit in Campile, and assuming we can work with this relative average deficit to calculate the absolute deficit (which actually is a little more complicated) we’ve a lack of 330 mm so we have only had 420 mm this year (which is less than Tunis!).

As a consequence, the natural vegetation around Campile has suffered tremendously. Some trees that depend on permanent (subterraneous) water, such as alder trees have died completely in and around Campile. Even drought-adapted species such as holm and cork oak have suffered; in certain locations some had lost their leaves by the end of September.

One term I learned from my permaculture teacher at the University of Wageningen is the term ‘ecoliteracy’ which he explained as the capacity to read a landscape. This year, I have been able to put this to the test in Corsica and the results are intriguing. The vegetation on north-facing slopes have dealt relatively well with the drought while vegetation on southern and western slopes has suffered tremendously from the drought. Why this discrepancy? Probably because of differing evapotranspiration rates. Northern slopes are the coldest and darkest slopes while southern and western slopes are the hottest and brightest slopes (in the Northern hemisphere). Put bluntly, vegetation on northern slopes has more shade (and hence protection against evapotranspiration) than vegetation on south/west -facing slopes.

I know south-facing slopes close to Campile, where trees had lost the majority of their leaves by the end of August!

The question that we should pose ourselves is, does this year represent the new normal ? And if so, from when onwards?

Why? Because climate change will strongly impact Corsica. Temperatures will continue to increase and droughts will become longer and longer.

However, Corsica is well known for its large interannual variation in precipitation. It is quite normal to have two consecutive years with a precipitation deficit of around 40% followed by 3 years of a precipitation surplus of 30%. The average precipitation in many traditional villages at 600 m altitude such as Campile is around 750-850 mm per year.

The problem is that dry years like 2021 (only 420 mm in the first 10 months of the year) give Corsica a rainfall that’s less than Malaga, Palermo, and around the same as Tunis…(I know that November and December are important wet months in Corsica so the annual total precipitation will be higher than the total cumulus at this moment (beginning of November)).

The problem with climate change is this; even though it does not necessarily reduce average precipitation levels (most climate models predict no significant precipitation decline for Corsica), climate change will have a very strong impact on Corsica’s vegetation because of higher evapotranspiration rates (due to the higher temperatures), and because of longer periods without rain.

This combination will likely lead to the steady decline in deciduous trees (because they are not well-adapted to long periods of drought) and a migration to higher altitudes. Wildfires will occur more frequently, and evergreen species will mostly outcompete deciduous species when a new forest tries to establish after a fire.

Concerning chestnut cultivation, irrigation systems must be installed rapidly, especially on south-facing orchards that are particularly vulnerable to climate change. The problem is this; most chestnut orchards are found in places far away from villages and permanently flowing rivers so it is very hard and in many places even impossible to irrigate them…

This means that in my opinion, the future of many chestnut orchards is doomed by climate change. Despite the fact that chestnuts can resist droughts reasonably well, they are not truly Mediterranean trees (which is why they are not cultivated in lowlands, only in mountainous locations with higher rainfall, shorter summer drought, and lower temperatures) such as holm oak and cork oak.

Because it is practically impossible to irrigate chestnut orchards using both natural rivers (because there are hardly any permanently-flowing rivers in the mountains close to chestnut orchards) or village water, the only technically possible solution is the creation of ponds that store rainwater in the rainy season or that can be filled with water from mountain rivers that flow only in the rainy months of the year. To irrigate a chestnut orchard, you need to store hundreds or even thousands of m3 per ha… to give you an idea of the size of such ponds, with a depth of 2 metres, we need a pond with a surface area of 500 m2, so a pond of 25 x 20 x 2 m. In many orchards this is not possible because they are very steep. However, certain Corsican orchards are located in places that are not steep at all and it is therefore technically possible to create ponds.

What is preventing farmers from creating these kinds of ponds? Their creation is very energy and time-consuming as well as expensive and despite their high actual value, chestnuts do not make their farmers instant millionaires ;).

Concerning my microfarm in Campile, I have had no problems whatsoever with water for three key reasons. First, our mayor has repaired major leakages in winter so that the hamlet where my water comes from (Antibia) did not have any significant leakages this summer. Second, in Antibia, there were no people who left their faucets running during the nights in July and August… as has occurred in other parts of Campile unfortunately. Third, I used different agroecological techniques to reduce water usage (mulching, drip irrigation, irrigation in the evening). Altogether, the hamlet of Antibia + my farm + neighbouring gardens used around 4-5 m3 water per day in summer which is very little considering we were many people in August and a farm.

I have started to create a water retention pond that, once finished, can store around 56 m3 of water. This should be enough to water the food forest but not the vegetables in summer. I want to use rainwater to fill this pond in winter.

If Campile as a village wants to be truly drought-resilient, measures should be taken at community-scale rather than at a garden-scale. We need to create large reservoirs that store hundreds of preferably thousands of m3 and that can be filled by our sources in winter when there is low water consumption and a high flow rate of our sources. These reservoirs can be used in July and August in dry years when the village population puts a huge pressure on the slow-flowing sources. Moreover, if this stored water could be used to water our gardens, gardening does not compete over rare drinking water in summer. Theoretically this sounds easy to implement, but practically it is very difficult in the context of a small village located on the slope of a steep mountain. Where can reservoirs be built? On whose land? How to finance the construction of these reservoirs? How to treat the water so that its quality is guaranteed?

Furthermore, you could wonder if such a drastic project is truly necessary or not. Even this extreme year we managed to have (just) enough water, right? True but our sources’ flow rates will likely decrease even further in the coming decades (during dry years). Water is key and as villages like Campile have been facing massive rural depopulation for decades, it is in my opinion one of the most important issues to fix (together with alternative housing) to attract (young) people to repopulate these depopulated villages again. Without water, no agricultural development (which can be a potentially important economic activity allowing some young people to make a living) can be realised, further limiting the attractiveness of rural Corsican villages.

Concluding, 2021 has been an exceptionally dry year but climate change will increase the frequency of extreme years so instead of once every 10 years (for example), extremely dry years might occur once every 5 years (or more). This is worrisome because extremes are often more impactful than averages (think of minimum temperatures that determine which plants can grow where). The increased frequency of extreme droughts will probably drive many plant species (mostly deciduous trees) to and over their ecological limit and result in a major transition of Corsica’s mountainous vegetation (rather than coastal vegetation because this vegetation is already well-adapted to drought compared to mountainous vegetation which depend on much more precipitation).

Is 2021 the new normal? Not yet. Next year we could have an extremely wet year with 1200 mm of rain. It’s part of the game of Corsica’s climate. However, the fact that such a drought is already possible in 2021 is worrisome. It is a sign of the major transitions that we are awaiting in Corsica this century and shows that water management is of extreme importance to sustain Corsica’s population and agricultural activities.

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