Predicting the Distribution of Parthenium Weed (Parthenium Hysterophorus L.) Under Current and Future Climatic Conditions in Bhutan

Invasion, spread and establishment of invasive alien species in a new environment causes serious ecosystem perturbation and native species extinctions. The problem is further aggravated under climate change as some invasive alien species perform better under elevated temperature and carbon dioxide regimes. Currently unsuitable regions such as high-altitude areas and mountains are likely to become more suited to invasion under future climatic conditions. We have modelled the distribution of one of the most invasive alien species, parthenium weed (Parthenium hysterophorus L.) which is rapidly colonizing different parts of Bhutan. The study was implemented in R environment using BIOMOD2 package; an ensemble modelling platform for species distribution modelling. Under current climate scenario, about 2.83% (1,099.01 km2 ) of the country’s total area was predicted to be suitable for parthenium weed invasion, covering 17 out of the 20 districts in Bhutan. Under future climate scenarios, the highest suitability was predicted under RCP4.5 2050 period with about 5,419.69 km2 anticipated to be suitable. Except for Bumthang, all districts showed suitability to invasions under future climate scenarios. Generally, districts located in the west and south showed more suitability than those in the east and central region. The highest elevation of suitability was predicted to be at 2,931 m above sea level; an upward shift of about 753 m. Based on these findings, there is an urgent need to develop management programs and raise public awareness on the adverse impacts of parthenium weed in Bhutan