Assessing the impact of invasive plants in the Northern Western Ghats and surrounding savannas

Abstract

Invasive species are a leading cause of biodiversity loss, and identifying and prioritizing invasive species for management are major goals set by the Convention on Biodiversity (CBD, 2010). While steps towards this have been initiated, these goals remain largely unfulfilled in India. The Western Ghats are a global biodiversity hotspot that also harbour a large number of invasive plant species (IPS).There is a lack of comprehensive studies on the distribution and impact of IPS in this region. To address this knowledge gap, I used herbaria collections and literature surveys to map the spread of IPS in the Northern Western Ghats and Konkan regions (NWGK). Additionally, I conducted interviews of local experts using questionnaires to assess local abundance and impacts of IPS in this region. Combining these two approaches, I ranked IPS in NWGK based on their potential impacts. In a field study, I quantified the effects of increasing invasion on diversity and community composition in two savannas. And finally, for these savannas I estimated how increasing invasion changes the distribution of functional traits in these plant communities. I identified 79 IPS in this region, and provide a prioritized ranking for the major IPS based on their potential impact. The results from the field studies showed that the impacts of invasion were more severe for broadleaf savannas, with greater loss of species and more pronounced changes in the community composition, than for the fine-leaf savannas in this region. In both savannas, invaded communities showed an increase in traits associated with competitive ability and acquisitive resource use strategies. This is first comprehensive study on IPS in the NWGK region. The prioritized list of invasive plants will be useful for practitioners to make informed decisions about management of IPS. The greater loss of species and pronounced composition changes in broadleaf savannas suggest that it should be prioritized for conservation, management and future restoration. The increase in species with acquisitive strategy in invaded savannas can change rates of nutrient cycling in these savannas which can further influence the community composition and ecosystem functions.