The rapid expansion of palm oil plantations in the world’s tropical regions, particularly Indonesian Borneo, is becoming an increasingly significant source of global carbon emissions, a new study says. Writing in the journal Nature Climate Change, researchers from Stanford and Yale universities project that the continued expansion of plantations will add more than 558 million metric tons of carbon dioxide into the atmosphere by 2020 — an amount greater than all of Canada’s current fossil fuel emissions. Much of the expansion in recent decades has occurred in Indonesia, particularly on the island of Borneo, also known as Kalimantan. According to researchers, the loss of forest for palm oil plantations in Kalimantan led to the emission of more than 140 million metric tons of CO2 in 2010 alone, or the equivalent of the annual emissions of 28 million vehicles. About 80 percent of planting leases remained undeveloped in 2010, the study says. If all these leases are developed, more than one-third of Kalimantan’s lowlands outside of protected areas would be covered with palm oil plantations.