Abstract
Invasive species alter ecosystem structure and functioning, including impacts on native species, habitat alteration, and nutrient cycling. Among the 27 invasive plant species in Nepal, water hyacinth (Eichhornia crassipes) distribution is rapidly increasing in Lake Cluster of Pokhara Valley (LCPV) in the last several decades. We studied the effects of water hyacinth on threatened waterbird abundance, diversity, and physico-chemical parameters of water in the LCPV. We found areas with water hyacinth present (HP) had reduced threatened water bird abundance relative to areas where water hyacinth was absent (HA; p = 0.023). The occurrence of birds according to feeding guilds also varied between water hyacinth presence and absence habitats. Piscivorous birds were more abundant in HA areas than HP areas whereas insectivorous and omnivorous birds had greater abundance in HP areas than in HA areas. Threatened waterbird abundance and richness were greater in areas with greater water depth and overall bird abundance but declined in HP areas. Degraded water quality was also identified in HP areas. Our findings can be used as a baseline by lake managers and policy makers to develop strategies to remove or manage water hyacinth in LCPV to improve waterbird conservation.
Highlights
Biological invasions have adverse effects on ecosystem structure and functioning in terrestrial and aquatic ecosystems [1,2,3,4,5]
Major impacts of alien invasions include the loss of native species, habitat alteration, and deterioration of ecosystem productivity and nutrient cycling [6,7,8,9]
Mikania (Mikania micrantha) covers about 44% of the habitat of Greater one-horn rhino (Rhinoceros unicornis) in Chitwan National Park, Nepal, and has reduced the growth of primary grass and tree species resulting in limited forage for this species [4,5,10]
Summary
Biological invasions have adverse effects on ecosystem structure and functioning in terrestrial and aquatic ecosystems [1,2,3,4,5]. Major impacts of alien invasions include the loss of native species, habitat alteration, and deterioration of ecosystem productivity and nutrient cycling [6,7,8,9]. Other invasive plant species in Nepal alter ecosystems, including parthenium (Parthenium hysterophorus) in grasslands and residential areas, blue billygoat weed (Ageratum houstonianum) in agro-ecosystems, and water hyacinth (Eichhornia crassipes) in wetlands [5,8]. In Nepal, of 182 alien flowering plants, 27 species are considered invasive [11]. Among these invasive species, four species, siam weed (Chromolaena odorata), lantana (Lantana camara), mikania, and water hyacinth, are considered among the World’s 100 invasive species with the greatest negative impacts [15].
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