Today, of the 5,050 square kilometers of relatively pristine habitat left in the New Caledonia Biodiversity Hotspot, 4,000 are rainforests and 1,000 are low- to mid-altitude maquis. Sclerophyllous forest once covered roughly 23 percent of New Caledonia, but now only exists in a patch of about 45 square kilometers. This area itself is generally very degraded and fragmented into smaller patches of 20-30 hectares or less, which are surrounded by agricultural land. Current threats to the hotspot's biodiversity include:
New Caledonia has the largest known deposits of nickel in the world. Nickel mining generates about 90 percent of the region's foreign exchange and produces fully half of the world's nickel. However, this asset is also a threat to the hotspot's ecosystems. The impacts of the nickel mining industry have been devastating. Open-cast mining has led to large expanses of deforestation and habitat destruction, resulting in bare slopes and waste heaps. The erosion of mining devastated areas has caused the siltation and destruction of streams and offshore coral reef areas and the pollution of water supplies.
The most valuable timber species are already gone from the hotpsot, but even limited logging threatens the habitats of species with highly restricted ranges.
Like other islands in the Pacific, hunting and habitat modification since the arrival of the first humans has led to a number of extinctions, including 11 species of non-passerine birds, and continues to pose a threat to the New Caledonian imperial-pigeon (Ducula goliath) and to flying foxes. International demand for rare species of birds and marine animals, such as the Vulnerable horned parakeet (Eunymphicus cornutus) and an endemic "living fossil" cephalopod (Nautilus macromphalus), threatens the already sparse populations of these species.
The intentional and accidental introduction of alien species in the hotspot for food or recreational purposes has been devastating. There are nearly 800 alien plant species, more than 400 alien invertebrates and some 35 alien vertebrates established on the islands (including an introduced amphibian), out-competing and replacing much of the original vegetation and faunal species. Among the most problematic of these introductions have probably been the black rat (Rattus rattus), the Javan deer (Rusa timorensis) and the fire ant (Wasmannia auropunctata). Pigs, cats, deer and rats occur from sea level to the highest elevations, and are present throughout the main island. The combined effect of these four species is rapidly destroying species and ecosystems.