Flying over the Indonesian half of the island of New Guinea, rainforest  stretches like a sea of green, broken only by rugged mountain ranges and  winding rivers. The verdant canopy shows little sign of human  influence.  But as you near Jayapura, the provincial capital of Papua,  the tree cover becomes patchier — a sign of logging — and red scars from  mining appear before giving way to the monotonous dark green of oil  palm plantations and, finally, grasslands and urban areas.