Invasive plant species are non-native plants that establish, spread, and cause ecological or economic harm in new environments. In Nepal, several invasive plants have become serious threats to biodiversity, agriculture, and natural ecosystems. Notable examples include Lantana camara, a woody shrub invading forest margins and grasslands; Mikania micrantha, a fast-growing vine smothering crops and native vegetation; Pistia stratiotes (water lettuce), clogging wetlands and water bodies; and Sphagneticola trilobata (Singapore daisy), forming dense mats along riverbanks and irrigation canals. These species outcompete native plants, alter habitats, and disrupt ecosystem functions, making their management a critical priority for conservation and sustainable land use in Nepal.
The aquatic plant Pistia stratiotes—commonly known as water lettuce—is a free-floating perennial in the arum family (Araceae). It forms soft, light-green rosettes of leaves that float on the surface of slow-moving waters, with its roots hanging beneath. In Nepal, water lettuce is recognised as an invasive alien plant species. It has been reported in wetlands and lakes, where dense mats of the plant can block sunlight, reduce oxygen exchange and out-compete native aquatic flora and fauna. Research has even projected a potential 9-fold increase in climatically suitable habitat for this species in Nepal in coming decades owing to climate change. Because of these impacts, its presence in Nepali water bodies raises serious concerns for the health of wetland ecosystems, biodiversity conservation, and the livelihoods of communities relying on those waters.The shrub Lantana camara, originally from Central and South America, is now globally widespread and ranked among the “100 worst” invasive alien species. It was introduced in South Asia likely as an ornamental plant and hedge species. In Nepal, Lantana camara has become a serious ecological threat. It thrives across a wide altitude range (from ≈100 m to ~1950 m) in forest margins, fallow lands, grasslands and roadside habitats. Studies show that in invaded sites plant species richness, diversity and evenness drop significantly compared to non-invaded areas; the soil microbial population is also adversely affected. Its rapid growth, high seed production (dispersed by birds), ability to resprout when cut, tolerance to disturbance and shade-fractured habitats make it difficult to control. Because of its aggressive spread, Lantana camara is reducing native vegetation cover, hindering forest regeneration and altering soil nutrient dynamics in Nepal’s ecosystems.Sphagneticola trilobata, commonly known as Singapore daisy, is a fast-growing, mat-forming herb native to Central America but now recognized as one of the world’s worst invasive species. In Nepal, it was first recorded in the Panchkhal area of Kavrepalanchowk District, where it has spread rapidly along roadsides, riverbanks, and irrigation canals. The plant forms dense ground covers that suppress native vegetation and hinder natural regeneration. Due to its ability to root easily from stem fragments and tolerate a wide range of conditions, S. trilobata poses a growing ecological threat to Nepal’s wetland and riparian ecosystems.
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