Management and restoration of the mining maquis ecosystem in New Caledonia (South West Pacific)

New Caledonia is a French overseas territory located in the southwest Pacific, 2000 km east of Australia. Geologically, the Antarctic and Australian plates broke up 250 Ma ago as a result of the break-up of Gondwana land. Ocean basins opened up and remnants of the former supercontinent separated and drifted eastwards. The eastern ridge, known as Norfolk ridge, substratum of New-Caledonia sank under the water. The New Caledonian Great Land emerged 34 million years ago after obduction phase. A new terrestrial environment was created. Freshly emerged, it was gradually recolonized by animals and plants from more or less nearby land masses.

New Caledonia’s Island isolation and the particularity of its soils forced the biotope to adapt and develop original, even unique, characteristics, thus contributing to making it one of the world's champions of biodiversity. With 76% plant endemism, this tiny territory (<20,000 km2) ranks third in the world (behind Hawaii and NZ).

The peridotites brought to the surface by obduction developed a thick alteration profile. Nickel and Cobalt, issued from the primary minerals of the peridotites, got concentrated in the saprolite horizon. The exploitation of these ores, was accelerated after the Second World War with the mechanization of extraction. Carried out without precaution, this time-period resulted in very significant environmental damage: deforestation and soil exposure, accelerated erosion, watercourse siltation and hypersedimentation, and flooded low-lying valleys. 

Environmental awareness was finally raised in the 1970s and increasingly triggered the introduction of responsible regulations. The mining and metallurgy companies working in the area, which are among the world's major players, have significantly improved their operational procedures, the quality of their environmental monitoring and remediation methods

On steep slopes and in a climate where rainfall can be very heavy, water management is one of the challenges to be overcome, as well as the revegetation of workings and slopes. This paper will present the results of the audit carried out by the GEME (mine water management and environment) program of the CNRT "Nickel and Environment" (National Technological Research Centre) on these issues and their comparison, based on the benchmark carried out with those of other major mining countries. The results concern the hydro-sedimentary models used, the acquisition of the parameters introduced, the adequacy with the rules of good practice and the evolution of these rules with global changes as well as the effectiveness of water management and revegetation methods.

The increasing involvement of local populations in the environmental management of the sites affected by mining will be discussed. Most of the mines are located on customary land whose inhabitants are now severely impacted by the mistakes of the past and want to become key players of the mine of the future. In a sensitive political context (end of the Nouméa Accord) where the institutional future of the country has not yet been determined, the topic of nickel mining and its environment is one of the levers for a hoped-for end to the crisis. Our communication will mention this in its conclusion.