WORLD leaders are currently meeting in Glasgow to discuss issues of global warming at COP26, many of which concern agriculture. But did you know that there is already one way, at least on a small scale, to grow vegetables and fruits in all seasons, and one that requires little intervention. The concept comes from Bolivia and takes the form of a semi-underground greenhouse. It's called a walipini.

Tomatoes for Halloween. Pumpkins at the start of summer. And strawberries on the Christmas table in the northern hemisphere this just seems wrong, given the importance of choosing seasonal fruits and vegetables to preserve the environment. But with rising temperatures and a succession of droughts, many crops are being threatened. However, there is an agricultural approach that can help maintain production of certain fruits in the face of climate change all without destroying an inch of the planet.


Taking advantage of thermal inertia

It's not an impossible equation: those in Bolivia and elsewhere in South America have been growing fruits and vegetables in all seasons for a few decades now thanks to walipinis. These are greenhouses situated partially underground that even (highly motivated) amateur gardeners can build. In fact, contrary to what many think, it does not get colder and colder as we dig into the ground. The temperature is constant as one descends.

Take wine as an example. Lovers of fine wines covet a natural cellar for good reason. It is an ideal underground environment for preserving these beverages thanks to the cool temperature that doesn't change, an essential parameter for the aging of wine. In the case of a walipini, it's the same principle. It functions as a kind of cellar in which you grow the plants of your choice.

By reaching a depth where the temperature is between 10 and 12°C, there is no need for the gardener to warm up the greenhouse as is for an above-ground installation. For a walipini, the heat of the day is retained at night, which prevents the plantations from freezing during cold periods. To obtain the desired effect, one must dig 2 to 2.5 meters deep.

Another characteristic is that the walipini is rectangular in shape and that the orientation of one of its long sides is exposed to the south. Also, the installation is recognizable through the slope of the roof so that the sun's rays penetrate at 90°.

However, such a project not only requires a lot of elbow grease, it also necessitates some precautions starting with the establishment of a ventilation system and a way to collect water.