The impact of climate change on the distribution of two threatened Dipterocarp trees

Abstract

Two ecologically and economically important, and threatened Dipterocarp trees Sal (Shorea robusta) and Garjan (Dipterocarpus turbinatus) form mono‐specific canopies in dry deciduous, moist deciduous, evergreen, and semievergreen forests across South Asia and continental parts of Southeast Asia. They provide valuable timber and play an important role in the economy of many Asian countries. However, both Dipterocarp trees are threatened by continuing forest clearing, habitat alteration, and global climate change. While climatic regimes in the Asian tropics are changing, research on climate change‐driven shifts in the distribution of tropical Asian trees is limited. We applied a bioclimatic modeling approach to these two Dipterocarp trees Sal and Garjan. We used presence‐only records for the tree species, five bioclimatic variables, and selected two climatic scenarios (RCP4.5: an optimistic scenario and RCP8.5: a pessimistic scenario) and three global climate models (GCMs) to encompass the full range of variation in the models. We modeled climate space suitability for both species, projected to 2070, using a climate envelope modeling tool “MaxEnt” (the maximum entropy algorithm). Annual precipitation was the key bioclimatic variable in all GCMs for explaining the current and future distributions of Sal and Garjan (Sal: 49.97 ± 1.33; Garjan: 37.63 ± 1.19). Our models predict that suitable climate space for Sal will decline by 24% and 34% (the mean of the three GCMs) by 2070 under RCP4.5 and RCP8.5, respectively. In contrast, the consequences of imminent climate change appear less severe for Garjan, with a decline of 17% and 27% under RCP4.5 and RCP8.5, respectively. The findings of this study can be used to set conservation guidelines for Sal and Garjan by identifying vulnerable habitats in the region. In addition, the natural habitats of Sal and Garjan can be categorized as low to high risk under changing climates where artificial regeneration should be undertaken for forest restoration.

Shifts in potential geographical distribution of Pterocarya stenoptera under climate change scenarios in China

“…For example, photosynthesis will reach an upper limit in plants with increased temperature although the response will vary based on the plant species. As a consequence, it can lead to local or regional species disappearance, as well as the loss of entire ecosystems or other substituents by other ecosystems (Deb et al, 2017a; Zhang et al, 2018). The models employed here demonstrate that the spatial extent of suitable climate available for P. stenoptera is expected to expand geographically, especially in a northerly direction.…”

“…Moreover, alterations in the temperature and precipitation regime potentially give rise to the shifts of P. stenoptera species phenologically, which may also indirectly affect the dependent faunal and floral species. Moreover, those changes may also have adverse effects on a number of terrestrial insects, mammals, and birds that are indirectly or directly dependent on the seeds, fruits, and flowers from P. stenoptera (Butt et al, 2015; Deb et al, 2017a).…”

MODELING SPECIES DISTRIBUTION OF SHOREA GUISO (BLANCO) BLUME AND PARASHOREA MALAANONAN (BLANCO) MERR IN MOUNT MAKILING FOREST RESERVE USING MAXENT

“…Maxent, based on georeferenced occurrence records and environmental, derives the probability of species. It has advantages over other SDMs as it requires species presence-only data, both continuous and categorical variables can be used in Maxent (Deb et al, 2017). During modeling, 75% of the species occurrence data were used as training data to generate species distribution models, and the remaining 25% were kept as testing data to test the accuracy of each model (Deb et al, 2017;Garcia et al, 2013).…”

“…Globally, it is estimated that 20-30% of plant and animal species will be at higher risk of extinction due to global warming; a significant portion of endemic species may become extinct by the year 2050 or 2100 consequently as global mean temperatures exceed 2-3 °C above pre-industrial levels (Garcia et al, 2013). Over the last three decades, the global climate change has produced numerous shifts in species distribution and in the near future, it is likely to act as a major cause of species extinctioneither directly or collegially with other drivers of extinction (Deb et al, 2017). Hence, intensifying endangerment and extinction of species that are already vulnerable, particularly those with strict habitat requirements and dispersal capabilities (Banag et al, 2015;Garcia et al, 2013).…”

“…The dipterocarps grow in evergreen, semi-evergreen, and deciduous forests. This characteristic of dipterocarps, when it comes to geographical range, flowering phenology, fruiting phenology, and ecological characteristic, makes them highly variable (Deb et al, 2017). Guijo (Shorea guiso) and Bagtikan (Parashorea malaanonan) are part of the dominant dipterocarp trees in (MMFR) and are classified as Critically Endangered and Vulnerable in the International Union for Conservation of Nature (IUCN) Red List (2017), respectively.…”