Predicting the distribution of rubber trees (Hevea brasiliensis) through ecological niche modelling with climate, soil, topography and socioeconomic factors

Identifying the factors that contribute to species distribution will help determine the impact of the changing climate on species' range contraction and expansion. Ecological niche modelling is used to analyze the present and potential future distribution of rubber trees (Hevea brasiliensis) in two biogeographically distinct regions of India i.e., the Western Ghats (WG) and Northeast (NE). The rubber tree is an economically important plantation species, and therefore factors other than climate may play a significant role in determining its occurrence. To assist in future planning, we used the maximum entropy model to predict plausible areas for the expansion of rubber tree plantations under a changing climate scenario. Inclusion of elevation, soil and socioeconomic factors into the model did not result in a significant increase in the model accuracy estimates over the bioclimatic model (AUC > 0.92), but their effect was pronounced in the predicted probability scoring of species occurrence. Among various factors, elevation, rooting condition, village population and agricultural labour availability contributed substantially to the model in the NE region, whereas for the WG region, climate was the most important contributing factor for rubber tree distribution. We found that more areas would be suitable for rubber tree plantation in the NE region, whereas further expansion would be limited in the WG region under the projected climate scenario for 2050.