Invasive Alien Plant Species in Wetlands of Kanchanpur District, Far Western Nepal

Abstract

Wetlands have a significant role in conservation of biodiversity and genetic resources but this important habitat has been degrading worldwide due to biological invasions and other anthropogenic activities. Successful management of wetland invasive plants requires a comprehensive information, including spatial distribution of invasive species, understanding the drivers of invasions, determining risk of invasion at currently unoccupied sites, and prioritizing control and management efforts. However, comprehensive study on the plant invasions in most of the wetland is still awaiting in Nepal. This study aimed to 1) identify invasive alien plant species (IAPS) invading wetlands of Kanchanpur district; 2) undertake spatial distribution mapping of IAPS in these wetlands; 3) prioritize major dispersal pathways of wetland IAPS for management; and 4) identify major drivers responsible for IAPS invasions in wetlands. This study was carried out in different 19 wetlands of Kanchanpur districts. Cover of IAPS were estimated visually; potential dispersal pathways of Eichhornia crassipes were identified by Focus Group Discussion with subsequent prioritization by scoring method; nitrogen and phosphorus content were measured in water samples; and major drivers of wetland invasions were identified by multivariate analyses. Of the six wetland IAPS found in Nepal, four were recorded in the wetlands of Kanchnapur district. Spatial distribution map of these four wetland IAPS was prepared by using geographical coordinates. The most frequently occurring and problematic IAPS were Ipomoea carnea ssp fistulosa with frequency 63% and Eichhornia crassipes with frequency 42%. Though the frequency of Eichhornia crassipes was less than that of Ipomoea carnea ssp fistulosa, E. crassipes was found to be dominant in terms of coverage. Intentional introduction of E. crassipes for feeding fishes was found to be major pathway of dispersal, followed by the intentional introduction for ornamental value, and by flooding. It has been found that 26% of the wetlands of Kanchanpur district were highly invaded (i.e., Cover of IAPS > 50%) by these IAPS, 42% were moderately invaded (Cover < 50%), and 31% were free of invasion. We found that variables such as the distance to road and settlements, nutrient content, elevation, and other disturbances such as grazing facilitate the plant invasions in wetlands. It has been found that lowland wetlands near road and settlements are at the highest risk of invasion from these species. Regular monitoring and proper management strategies can reduce and prevent their spread to the noninvaded