Invasive alien plants in South Asia: Impacts and management

South Asia is home to an immense diversity of flora and fauna, which makes it one of the global biodiversity hotspots. Plant invasions are one of several factors that threaten South-Asian biodiversity. This review lists problematic invasive plant species, analyses their negative impacts, and summarises management methods implemented in South Asia using data obtained from research articles and relevant databases (CABI, GISD, GloNAF). The data was used to evaluate the research trends over time, knowledge of the impacts of invasive plants, and management measures aimed at the invasive species. In total, 392 currently invasive vascular plant species were recorded in South Asia. Of these, 41 species are widely distributed in South Asia, occurring in at least three countries, and 20 species that are listed as invasive in South-Asian countries by the book Invasive Plant Species of the World are considered as the most problematic. For a subset of the most problematic species where such information is available, we present management measures that are in place in individual countries. The number of studies on invasive species in South Asia has been increasing, with more than half (53%) represented by local and regional inventories. Among the countries in South Asia, India has the highest number of invasive (145) and naturalized plant species (471). However, the percentage contribution of invasive and naturalized species to the native flora is the highest in the Maldives Islands. Studies on impacts are limited to those on native plants and agriculture; there is a lack of research on impacts on ecosystems and hydrology, as well as on economic costs and human health. Moreover, impacts have been quantified for very few species. Currently, the management of invasive plants is mostly done by physical or mechanical methods; research into opportunities for biological control is inadequate. Our review highlights the urgent need to quantify the impacts of all prevalent and problematic invasive species in South Asia as a crucial step in allocating resources for their management and addressing the knowledge gap in this region.