The surface area of the nine glaciers now totals 79ha compared with 140ha 17 years ago.
"We are seeing the disappearance of the symbol of the Pyrenean landscape in the high mountains," René said.
He said mountainsides may begin to crumble without the "cementing effect" of glacier ice.
The Pic d'Arriel glacier, in the west of the Pyrenees, disappeared permanently following a heatwave last summer, the Pyrenees Climate Change Observatory, another environmental group, reported in November.
Sophie Cauvy-Fraunié, of the French Agricultural Research Institute, said: "Organisms adapted to special conditions, cold and cloudy water where little light penetrates, live in glaciers and the rivers they feed. They can be micro-invertebrates, bacteria and fungi.
"If species endemic to the Pyrenees depend on the influence of glaciers, it is probable that they will become extinct."
The Aneto glacier, at one of the highest points in the Pyrenees, is shrinking rapidly, according to Christophe Dedieu of the Météo Pyrénées website.
"It was 100m thick in the 20th century, but now only 10 to 20m are left."
Higher summer temperatures cause snow that falls in winter to melt faster, leaving glacier ice exposed and more prone to melt, Dedieu said.
Combined with decreasing winter snowfall in recent years, the effect has been devastating.