Google street view reveals new insight into the distribution of panicum maximum in Sri Lanka

Abstract

The alien invasive species (AIS) Panicum maximum causes negative impacts on the ecosystem by out-competing native vegetation, creating fire hazards during dry periods, and blocking access to animals. Panicum maximum has a wide distribution in Sri Lanka, while an accurate estimation of its distribution has not yet been determined. Estimating the current distribution of P. maximum in the island is vital to develop management strategies to control its spread. Thus, the objectives of the current study were to map and model the distribution of P. maximum in Sri Lanka. Google Street View (GSV) images have been used previously as a low-cost method to map the distribution of several animal and plant species. Thus, the mapping of P. maximum was conducted using GSV data, Google Earth Pro and QGIS software. The presence and absence data of P. maximum covering the entire island were recorded from 50,231 and 30,950 data points from GSV images taken during 2015-2016 and 2020-2022, respectively. The distribution maps were generated separately for each district, depicting the presence and absence of P. maximum. The density distribution maps of P. maximum were prepared for each district and the entire country using the same data sets. Heat maps can be used to predict the density of the species distribution. P. maximum is mainly distributed in the wet and intermediate zones of the country, with a limited distribution in the dry zone. Compared to 2015-2016, a higher distribution of P. maximum was observed in 2020-2022. During 2015-2016, the lowest distribution (<10%) was reported in the Northern Province, particularly Trincomalee and Batticaloa districts. The highest distribution of P. maximum (>80% of the total area) was reported from Polonnaruwa, Kurunegala. Kandy and Galle districts. A comparison of the distribution of P. maximum during 2015-2016 and 2020- 2022 revealed a 2-11% increase in the spread of P. maximum in 11 districts thus a further spreading of the species can be expected, especially in wet and intermediate zones where its distribution is high.