Source : PNRHL-DR
Haut-Languedoc, located on the southern limit of the Massif Central, is located in a unique climate confluence zone. Different climates - Mediterranean, Atlantic, mountainous or oceanic - overlap in this relatively small area. It is - and will be - one of the ecosystems of France most affected by climate change.
Thus the Mediterranean climate is very close to the mountain climate in certain sectors of the Regional Natural Park, and this geographical proximity induces a stronger sensitivity of the territory. A small change can have important consequences. The effects will be clear on the vegetation, more vulnerable to sudden changes, especially as the hazard will be marked. The rise of the Mediterranean climate will be done in successive waves in the higher elevation zones, and not in a progressive way.
In France, no trend is currently observed for precipitation, although in the Regional Natural Park of Haut Languedoc there is a decrease in summer precipitation. This decline, combined with an increase in winter temperatures and precipitation, indicates that the Mediterranean climate is becoming stronger throughout the territory.
In 2003 in the Tarn, we observed the same climate in Marseille in some sectors: we are in a scenario of climatic rise in fits and starts. As a result of this exceptional heat wave, many Douglas-fir stands underwent decay after 90 days with an average daily temperature of 30 ° C in the shade, without rain.
Source : IGN, orthophotograhs 2001 abd 2003, PNRHL
An aerial photography campaign of the IGN just after the heat wave made it possible to highlight tasks of dying stands, because the crown of dead Douglas trees immediately blushed in some plots.
After studying stand maps and aerial photographs, it was found that 65% of the inventoried stands were affected by mortality distributed in spots on the plot. However this mortality is diffuse since only 3 to 5% of the surface of Douglas-fir is affected by mortality on the territory of the Regional Natural Park of Haut Languedoc.