Mikania micrantha
An invasive species is a plant, fungus, or animal species that is not native to a specific location (an introduced species), and which has a tendency to spread to a degree believed to cause damage to the environment, human economy or human health (Colautti & MacIsaac, 2004) . Similarly, a species, subspecies or lower taxon, introduced outside its natural past or present distribution; includes any part, gametes, seeds, eggs, or propagules of such species that might survive and subsequently reproduce is called an alien species (Convention on Biological DIversity (CBD), 2002)
The USDA defines an alien plant as “not native to the continent on which is now found.’’ (Dyer, 2015). For example, plants that are native to Europe are exotic in North America, and plants native to North America are exotic in Japan. Exotic plants may or may not be invasive, although some may become invasive in the future. Not all alien species become invasive but often this results because the new environment does not contain the same ecological pressures as the original one. Thus the alien species can multiply without control (UN Environment, WCMC, 2014). Invasive species can harm both the natural resources in an ecosystem as well as threaten human use of these resources (Fei, Phillips, & Shouse, 2014).
Ageratum conyzoides
Ecologically and in silviculture abrupt introduction of a new species to an area affects the species composition. Therefore invasive species are considered as second most important threat to biodiversity; next to habitat fragmentation since they are important drivers of ecosystem change and alteration of food webs. Their positive impacts also are taken into consideration; ornamental value, option and existence value are the examples. These sometimes have lightened the controversial statements, whether invasive species are friends or foe, pests or providence and weed or wonder (Rai, Scarborough, Subedi, & Lamichhane, 2012). An assessment of invasive alien plant species (IAPS) was undertaken for the first time by IUCN Nepal during 2002- 2003 and reported 21 naturalized (i.e. alien species with self-sustaining population) flowering plant species to be invasive in Nepal (Tiwari, Adhikari, Siwakoti, & Subedi, 2005) . In addition to them, four naturalized species Ageratum conyzoides, Erigeron karvinskianus, Galinsoga quadriradiata and Spermacoce alata Aubl (Syn. Borreria alata ) have been also found to be invasive in agro-ecosystems and rangelands (Shrestha, Shabbir, & Adkkins, 2015).
Lantana camara
Expansion of invasive alien species (IAS) is a global problem which has impoverished native biodiversity and disrupted ecosystems from aquatic habitats, wetlands, grasslands to forested areas. Rapid expansion of IAS into forest ecosystems of Nepal in last few decades has posed a serious threat to forest health with possible impact to carbon balance (BS JV API, 2013). Species invasion is profoundly altering communities and ecosystem worldwide (Gurevitch & Padilla, 2004).
The ecological and evolutionary impacts include extinction of species, modification of ecosystem process (e.g. nutrient cycling, fire regime, hydrology), and evolution. For example, about 42% of the species on the threatened or endangered species list are at risk primarily due to alien species (Pimentel, Lach, Zuniga, & Morrison, 2000).
In Nepal, the IAPS are already common and spreading rapidly both in anthropogenic as well as in natural landscape but their impacts – economical, ecological and evolutionary – have not been evaluated comprehensively. Limited researches and case studies have shown that the impacts of IAPS range from habitat degradation of endangered wildlife (e.g., one-horned Rhinoceros, (Murphy, et al., 2013) to negative effects on the livelihood of rural communities (Rai, Scarborough, Subedi, & Lamichhane, 2012). Murphy, et al., (2013) reported that 44% of the habitat of endangered one-horned rhinoceros in Chitwan National Park has been negatively affected by Mikania micrantha by suppressing growth of grasses and regeneration of trees. Another IAPS Parthenium hysterophorus has significantly altered species composition and soil chemistry of grasslands (Timsina, Shrestha, Rokaya, & Munzbergova, 2011). The cases of bitter taste in milk produced by cattle that grazed in P. hysterophorus invaded grassland, and allergic dermatitis due to this weed to human have been also reported (Shrestha, Shabbir, & Adkkins, 2015). Other IAPS of the terrestrial ecosystems such as Ageratina adenophora, Lantana camara and Chromolaena odorata are also widespread and form monoculture stands displacing native species and disrupting ecosystem processes. They have reduced carrying capacity of rangelands, increased the risk of fire damage, and prevented regeneration of other species including trees.
Parthenium hysterophorus
Although invasive species can have direct effects on many of these goods and services, it is important to recognize that these effects can also be greatly influenced by interactions with fire, weather and climate patterns, land use changes, and other disturbances. The influence of invasive species on critical natural resources may be increased or decreased in the context of other disturbances (Dix, 2009).
Several studies have been conducted in Nepal related to invasive species such as, Tiwari et al. 2005, Siwakoti 2012, Sukhorukov 2014, Budha 2015, Poudel and Thapa 2012.Most of them have focused on finding type and number of invasive species in Nepal such as Tiwari et al. 2015, reported 219 alien species of flowering plants. The study were concentrated in some parts of Nepal like Darchula, Siwalik, Mid hills and Low Mountains from east to west, but, few study have been done relating to invasive species in Shivapuri Nagarjun National Park, as well as, few study have shown invasive species diversity, relationship between disturbance and invasive species.
Mikania micrantha is an aggressive IAS colonizing relatively moist habitats such as wetlands, grasslands, shrub lands, and riverine forests. First observed in Nepal in 1963 by Japanese expedition team in the eastern part (Tiwari, Adhikari, Siwakoti, & Subedi, 2005), the weed, it is advancing westward from eastern Nepal. The westernmost distribution range of M. micrantha in Nepal is Kapilvastu district (Tiwari, Adhikari, Siwakoti, & Subedi, 2005). (Siwakoti, Mikania Weed: A Challenge for Conservationists., 2007) reported this species from the Lumbini Sacred Garden of Kapilvastu. More than half of the area of Koshi Tappu Wildlife Reserve (KTWR) has been invaded by M. micrantha while in the surrounding community forests in buffer zone; the abundance of M. micrantha is relatively low due to the periodic removal of its biomass by forest users’ group (Siwakoti, A checklist of angiospermic flora in and around Lumbini Sacred Garden, 2008).In Chitwan National Park (CNP), Mikania micrantha is common in riverine forests, mixed hardwood forests, wetlands, tall grasslands, short grasslands, and sal forest (in order of decreasing abundance of M. micrantha) (Department of National Parks and Wildlife Conservation (DNPWC), 2009).
Eichhornia crassipes
This weed was present in about 44% of the assessed plots in rhino habitats. In Chitwan NP, (Sapkota, 2007) also reported high abundance of M. micrantha in natural stands of Bombax ceiba and plantations of Dalbergia sissoo with negative impact to growth of seedlings and sapling (i.e. regeneration). Invasion by this weed also altered species composition of the understory vegetation in forests (Basnet, 2011).
Works Cited
Basnet, B. (2011). Impact of Mikania micrantha Invasion on Species Richness and Composition: A Case of. Kathmandu, Nepal: Central Department of Botany, Tribhuvan University.
BS JV API. (2013). Study on Invasive Alien Species (IAS) as Drivers to Deforestation and Degradation of. Kathmandu: Ministry of Forest and Soil Conservation.
Colautti, R. I., & MacIsaac, H. J. (2004, March). A neural terminology to define ‘Invasive Species’. Diversity and Distributions, 135-141.
Convention on Biological DIversity (CBD). (2002). Alien species that threaten ecosystems, habitats and species. CBD. Montreal, Canada: Convention on Biological Diversity.
Department of National Parks and Wildlife Conservation (DNPWC). (2009). The Status and Distribution of The Greater One-Horned Rhino in Nepal. Kathmandu, Nepal: Department of National Parks and Wildlife Conservation (DNPWC).
Dix. (2009). A Dynamic Invasive Speciw Research Vision: Opportunities and Priorities. Chicago, US: Createspace.
Dyer, M. H. (2015). Gardening know how. Retrieved April 9, 2018, from Gardening know how: https://www.gardeningknowhow.com/plant-problems/weeds/invasive-noxious-plants.htm
Fei, S., Phillips, J., & Shouse, M. (2014). Biogeomorphic Impacts of Invasive Species. In S. Fei, J. Phillips, & M. SHouse, Annual Review of Ecology, Evolution, and Systematics (pp. 69-87). West Lafayette, Indiana: Purdue University.
Gurevitch, J., & Padilla, D. K. (2004). Are invasive species a major cause of extinctions? Trends in Ecology and Evolution, 19: 470-474.
Murphy, S. T., Subedi, N., Gnawali, S. R., Lamichhane, B. R., Upadhyay, G. P., Knock, R., et al. (2013). Invasive Mikania in Chitwan National Park, Nepal: The threat to the greater one horned rhinoceros and factors driving the invasion. Oryx 47, 361-368.
Pimentel, D., Lach, L., Zuniga, R., & Morrison, D. (2000). Environmental and economic costs associated with non-indigenous species in the United States. Bioscience, 50:53-65.
Rai, R. K., Scarborough, H., Subedi, N., & Lamichhane, B. (2012). Invasive Plants- Do they devastate or diversify rural livelihoods? Kathmandu.
Sapkota, L. (2007). Ecology and management issues of Mikania micrantha in Chitwan National Park, Nepal. . Banko Jankari, 17: 27-39.
Shrestha, B. B., Shabbir, A., & Adkkins, S. W. (2015). Parthenium hysterophorus in Nepal: a review of its weed status and possibilities for management. Weed Research, 132-144.
Siwakoti, M. (2007). Mikania Weed: A Challenge for Conservationists. Our Nature, 5: 70-74.
Siwakoti, M. (2008). A checklist of angiospermic flora in and around Lumbini Sacred Garden. Journal of Natural History Museum, 23: 27-44.
Timsina, B., Shrestha, B. B., Rokaya, M. B., & Munzbergova, Z. (2011). Impact of Parthenium hysterophorus L. invasion on Plant species composition and soil properties of grassland communities in Nepal Flora. 233-240.
Tiwari, S., Adhikari, B., Siwakoti, M., & Subedi, K. (2005). An Inventory and Assessment of Invasive Alien Plant Species of Nepal. Kathmandu: IUCN.
UN Environment, WCMC. (2014, October 21). Biodiversity a-z. Retrieved April 9, 2018, from Biodiversity a-z: http://www.biodiversitya-z.org/content/alien-invasive-species-ais
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