An area of rainforest nearly five times the size of London has been destroyed in the past two decades in Indonesian New Guinea, home to Asia Pacific’s largest area of intact old-growth forest, a new study shows.

More swaths of primary rainforest are expected to be cleared, as they stand in areas that have been allocated for oil palm and pulpwood concessions plantations and for the new roads to serve them.

The deforestation threatens many of the unique species in the region and will release huge volumes of greenhouse gases into the atmosphere, experts warn.

The Indonesian half of the island of New Guinea, also known as the Papua region, lost 748,640 hectares (1.85 million acres), or about 2% of its old-growth forest, between 2001 and 2019, according to the study published in the journal Biological Conservation.

This was largely due to the growth of plantations, primarily oil palms, and the government’s push for infrastructure development in the region, the study found. Oil palm and pulpwood plantations accounted for 208,223 hectares (514,500 acres) of the deforestation there during that period, or 28% of total deforestation.