CANYON

CANYONS: THE SAUVOUS GORGES.
A distressing configuration for human beings but a refuge for animals, the canyon gorges are transforming with climate change. Previously little frequented by fish because they were covered in fragile food chains, the canyons have become refuges for climatic migrants. Climate change has always existed on earth but it took place over long time scales. In two hundred years our climate has changed rapidly. Two hundred years represent a few thousandths of a second on a planetary scale since the 4.5 billion years since the creation of the Earth and 4 billion years since the appearance of the first life. Everything is happening too quickly, animals cannot adapt genetically to these sudden changes. So to survive, they organize, migrate, settle in new areas by upsetting the balances established since the dawn of our times on specific sites such as canyon gorges.
Each river profile presents a geological, physico-chemical and biological landscape. All profiles (riffles, channels, rapids, gorges, etc.) have precise and complementary roles in the life of the river. Rapid climate change can upset this balance. If this change is slow, these profiles can be compensatory between them. They can reorganize themselves quietly and welcome the animals. But if the change is too rapid, too intense as currently, the compensatory system no longer works. There remains only one Noah's Ark profile which absorbs all the stresses of the other profiles: the gorges. When the riffles are dry in summer or flooded in winter, washed out several times a year, they can no longer provide habitats rich in life. Sterilized, they become corridors of mud sheltering invasive algae, bacteria and threatening viruses. Populations of aquatic animals then move into refuge areas where the mass of water is constant, larger and fresher. The gorges have become real oases but for how long? Food production is limited there by a rapid solar course and is threatened by the over-watering of canyoners, destructive of the water people.