For the record, we are organic farmers and are convinced that organic farming not only helps us to make wines that are true expressions of their terroir, it helps tackle climate change. “How” you ask? By enhancing soil fertility without industrial fertilizers, reducing greenhouse gas emissions, storing carbon in the soil, and improving climate resilience through biodiversity.
But this record-breaking summer and a recent article in Science Advances, “Increased atmospheric vapor pressure deficit reduces global vegetation growth”, has brought into focus just how enormous the challenge is becoming. Check out Newsweek’s recap: “Global Vegetation Growth has Stalled…” The authors studied vapor pressure deficit (or VDP) which they found has been rising notably since the 1990s. Higher atmospheric VPD interferes with photosynthesis in plants, hindering growth and increasing the mortality rates of vegetation and forests.
It got us thinking… We pulled some data of our own, looking at our annual rainfall as well as our daily highest temperatures. Since the study highlighted the late 1990s as the tipping point, we decided to look at the last 25 years. In order to average the annual differences, we studied the numbers by five year segments.
What did the numbers tell us?
Our summers are increasingly hotter. We’ve gone from a total of 220 days of temperatures of 30°C or more during the earliest period to 367 days of similar temperatures for 2014 to 2018. That means since 1994, we’ve got a month more of 30°C plus temperatures!
Here’s what we discovered with respect to rainfall: a steady decline from an average yearly rainfall of 797mm between 1994 and 1998 to 577mm between 2014 and 2018. That’s a decrease of 28%!
So what does all this mean for us?
Increased temperatures cause plants to lose more moisture through transpiration. Couple that with limited rainfall and we face three major difficulties.
First and foremost, how do we ensure enough moisture for our vines? Since we can’t make it rain, nor stop the rise in temperatures, our only solutions must revolve around three axes: trapping moisture content in our soils, helping our vines limit their transpiration and bringing water through intelligent irrigation (here in Costières de Nîmes we’re blessed with the Canal Philippe-Lamour).
Second, how do we mitigate the impact of the proximity of various types of vegetation, whether it be cover crops or wooded areas? We pride ourselves in maintaining biodiversity with the woods, garrigue and cover crops that surround our vineyards. But surprisingly this year, the vineyards with cover crops fared worse, and the vines closest to the wooded areas suffered the most from heat stress.
Third, how do we determine the timing of the application of crucial plant health products? The first heat wave in June had devastating results for some organic growers who sprayed sulfur against oidium just before the forecasted heat-spike. The result was partially or even totally burned leaves and clusters. Thankfully, we resisted spraying at that time because of the forecast.
To meet these challenges, here’s what we already do:
This year we experimented with using kaolin as sunscreen for our vines.We already use this clay in our apple orchards to protect the fruit against sunburn and help with photosynthesis by lowering heat stress. Its added benefit is that it keeps certain pests at bay. So we gave it a go this year in the vineyards as well.
So what are we looking into for the future?
We’re convinced that there are many practices that farmers can adopt to make our vineyards more resilient to our changing climate. Luckily while other areas, such as Bordeaux, are dealing with varieties that are finding difficulty adapting to the increasing temperatures, southern Rhône varietals including Grenache, Syrah and Carignan are apparently adapting better to our changing climate. Some of our white varieties including Marsanne, Roussanne and Carignan Blanc are also well adapted. The four hectares of vineyards we’re planting this winter will include both Carignan Blanc and Grenache Gris. A new vineyard is a demonstration of our optimism for the future.
Here we have a saying, “when you plant Carignan, you plant for your grandchildren.”
As caretakers of our lands what’s more essential than preserving our vineyards for future generations?
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