denuded hills

I just saw a documentary on mining in new Caledonia and what struck from all the aerial shots is the lack of forests.
From the latitude and the climate, I would have expected there would be vast tracts of tropical rainforest.
So was there once rainforest and humans have cut it down or has it always been like this?

FYI-most of the earth looks like that now.

There are so-called "rain shadows" on Fiji, for example. One half of an island rainforest, the other half dry grassy hills. This has to do with direction of trade winds, etc. and not so much to do with human activity. Maybe the same process in New Caledonia.

Of course, there is also deforestation everywhere on the planet because of human activity. So in the film you saw, I don't know. Could be both possibilities depending on which part of the island you saw.

New Caledonia does suffer from its fair share of deforestation, but unlike many islands in the S Pacific is not a place with virgin tropical rainforests. Instead, it is a place of pine forests. In fact, it's famous for its pine forests.

To answer the question - it has always been like this (pines, not jungles) but copper mining and logging has taken a toll.