sentences:  The haze is largely caused by illegal agricultural fires due to industrial-scale slash-and-burn practices in Indonesia, especially from the provinces of South Sumatra and Riau in Indonesia's Sumatra island, and Kalimantan on Indonesian Borneo.Burned land can be sold at a higher price illegally, and eventually used for activities including oil palm and pulpwood production.Burning is also cheaper and faster compared to cutting and clearing using excavators or other machines.