The trans-boundary haze in Indonesia, Malaysia and Singapore happens almost every year due to forest fires in Indonesia. Many of these fires were started to clear land for smallholding or planting at plantations.[6] In 2019, fires have been burning in Sumatra and Kalimantan within Indonesia.[7] Sumatra and Kalimantan possess large areas of peatland, which is highly combustible during dry season. Peat, which is made up of layers of dead vegetation and other organic matter, contributed heavily to carbon emissions because of the substance's high density and carbon content.[8]