I think France's main environment problem is the pollution of water resources, though France has a law in water resources protection, which dates from 1964. Due to the accumulation of industrial contaminants, agricultural nitrates and waste from cities, water pollution is a serious problem. France has 180 cubic km of renewable water resources, 73% out of which are used in industry and 12 in farming.
The tap water is good only because the state spends millions every year for renewing and modernizing water filters. But, you can't predict which would be the water quality in several years if water pollution keeps increasing.
What other things in the matter of environment France has to fight?