Longitudinal trends of future suitable climate for conserving oil palm indicates refuges in tropical south-east Asia with comparisons to Africa and South America

Palms are crucial species to the flora of south-east (SE) Asia. Oil palm (OP) is a highly significant introduced species to the region and produces palm oil, an especially important commodity. OPs are grown in huge plantations in SE Asia, predominantly in Malaysia and Indonesia. These palms have detrimental effects on the environment, particularly from deforestation when creating new plantations. Future climate scenarios have indicated mostly reductions in suitable climate for growing OP throughout SE Asia and it is crucial to consider how the palms can be conserved. Climate change has been shown to stimulate poleward movements in some other species, which assist in conserving them and may permit assisted colonisation. However, poleward movement to these refuges is unlikely from the tropics. Recent research has indicated potential longitudinal refuges for OP in Africa and phased longitudinal refuges in South America, based on future suitable climate (SC) for growing OP. These data indicate how the sustainability of OP could be maintained rather than experiencing the complete decimation of the crop, which might otherwise occur. This current work was undertaken to determine trends of future SC for growing OP in SE Asia and to indicate refuges with implications for conservation and plantation management. The results are compared with those for Africa and South America. The longitudes considered in SE Asia were from 100 degrees E to 146 degrees E, which is an intentionally large area of land. The maps obtained from the climate modelling program CLIMEX, of climate suitability for growing OP, were employed to obtain the percentage SC in SE Asian regions and countries for current time (CT), 2050 and 2100. The average percentage SC decreased for 2050 and further for 2100. Increasing longitudinal trends in SC for growing OP were observed from CT to 2050, CT to 2100 and 2050 to 2100 from west to east. Vietnam, the Philippines, Papua New Guinea (PNG) and island Malaysia had increased SC by 2050. Large decreases in SC by 2050 for Thailand, Laos and Cambodia, which are towards the west of SE Asia, were observed. There was an increasing trend in suitable climate from CT to 2100 and a smaller trend from 2050 to 2100. Hence, OP may find suitable refuges by natural seed spreading towards the east of SE Asia, hence avoiding extinction. Similarly, new plantations could be established in the same direction, although environmental concerns are paramount. Vietnam, the Philippines, PNG and island Malaysia may become more suitable than Thailand, Laos and Cambodia. The sustainability of OP plantations is likely to decrease substantially with climate change. However, there is scope for a more sustainable situation towards the east of SE Asia. New plantations cannot be established without considering the severe effects on the environment from deforestation and increased greenhouse gases. Overall, urgent action is required to reduce the effects of climate change.