Invasive alien species are a major threat to biodiversity and can cause irreversible damage to nature, including local and global species extinctions and also threaten human well-being. Invasive species are non-active organisms that when introduced to a new environment, can cause harm to the ecosystem, economy, or human health. The global threat posed by invasive alien species is underappreciated, underestimated and often unacknowledged.
According to a major new report by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) more than 37,000 alien species have been introduced by many human activities to regions and biomes around the world. This conservation estimate is now rising at unprecedented rates. Many of these species are harmful invasive alien species – seriously threatening nature, nature’s contributions to people and good quality of life. It also reveals that alongside dramatic changes to biodiversity and ecosystems, the global economic cost of invasive alien species exceeded 423 billion dollars annually in 2019 with costs having at least quadrupled every decade since 1970. Many researchers opined that for the past several decades, the Invasive Alien Plant Species (IAPS) have posed severe threats to the local biodiversity, ecosystem services, environmental quality and human health. The spread of Invasive Alien Species is compounded by climate change which has impacted native biodiversity, ecosystem services and human being. Invasive aquatic species have created great threat to water bodies including lakes, rivers, ponds etc.
Among the rivers that flows in Manipur, Kongba River of Manipur is now facing the danger of degrading its aquatic ecosystem due to the presence of invasive aquatic species such as Water Hyacinth – Pontederiaazurea (local name: Kabo-Kang Awangbi), Pontederiacrassips (local name: Kabo-Kang Anembi) and Alternantheraphiloxeroides (local name: Kabo Napi) etc. These species are among the lists of invasive aquatic species published by National Biodiversity Authority (NBA). It sets a target to control all the invasive species by 2030.
Water hyacinth is a free-floating aquatic plant native to South America. The flower of water hyacinth is typically a light purple or lavender in color. It is known for its rapid growth rate and ability to form dense mats on the water’s surface. In India, water hyacinth was first introduced to India as ornamental plant. The British colonial government brought it to India for its beautiful flowers and to use it as a decorative plant in ornamental ponds and water gardens. The “Bengal terror of water hyacinth” was an instance which cause severe infestation of water hyacinth in the water bodies of Bengal, particularly the Hooghly River and its tributaries as it quickly spread and became a nuisance, clogging waterways and causing problems for navigation, fishing and agriculture.
On interacting with Imphal Review of Arts and Politics (IRAP) about the invasive aquatic species, Dr. Athokpam Pinokiyo, Associate Professor, Department of Botany (Plant Taxonomy and Biodiversity), Dhanamanjuri University (DMU), Manipur says that as water hyacinth can reproduce fast through both sexual reproduction and vegetative propagation it makes the biodiversity monotonous dominated by one species. It resulted in the loss of native plant species grown in the river and its banks. The rapid growth of water hyacinth forms thick layer like a mat which stopped the flow of river water which threaten the survival of all the aquatic lives of the river. With the lack of dissolved oxygen, the quality of water becomes degraded. As the water remains stagnant it forms a breeding place for mosquitoes and other infectious organisms which contribute to the ecological imbalance.
She added that one water hyacinth plant can produce three thousand seeds at one time. These seeds can remain viable at the sediments of the river for 24 years allowing water hyacinth to spread rapidly and form dense mats on the water’s surface. With the rise in temperature and rich-nutrient water it can germinate and grow into new plants. She pointed out some measures to control water hyacinth and other invasive aquatic plants such as mechanical control by physically removing the plants from the water using nets or aquatic weed harvesters, Biological control by introducing natural enemies of water hyacinth such as weevils and moths, chemical control by using herbicides, integrated methods by combining different control methods, community involvement and regular monitoring of water bodies and research on effective methods which can help improve management strategies.
In this regard, Dr Khuraijam Usha, Department of Environmental Sciences, Dhanamanjuri University (DMU), Manipur expressed that the invasive species dominate the soil and the ecosystem resulting in the loss of native species. Now, invasive species becomes a big threat to the global biodiversity, ecosystem services and function, human livelihoods and health and economy. In Manipur, it was introduced by chance or accident or as ornamental flower. There were stories even the flowers of water hyacinth were presented to the Kings of Manipur as gifts. But now it creates many problems including the environmental issue which is of great concerned because it dominated the native species.
Dr Usha highlighted that as water hyacinth is spongy and floating it can be carried in any direction of the wind. Sunlight cannot enter the water as it acts as a thick carpet. Without sunlight all species such as aquatic organisms, plants, macrophytes, submerged species etc. cannot perform their food making process-photosynthesis, disturb respiration and other activities resulting in the disturbance of the water ecosystem of the river. This effects the survival of aquatic lives that dwelled in the river. The massive presence of water hyacinth deteriorates the quality of water. With the continuous process of decomposition, the level of Oxygen is decreased which create a threat to the survival of aquatic lives. This will slowly bring to the dead of water bodies in the state.
Moreover, the NPK fertilizers which flows from the paddy fields enriched more growth of the plants and the process of Eutrophication also enriched. If the situation remains as it is, many fresh water bodies like rivers will convert into wetlands and if wetlands are not control in time, it will convert into dry lands. Porompat and Keishampat are clear examples how water bodies are converted into dry lands, she added. Dr Usha appeals if any species is found fast growing and dominating the native species, it needs to be identified whether it is invasive or not by consultation of the experts.
The maximum length of the river is found covered mainly by water hyacinth. As water hyacinth is a significant invasive species in Kongba River, it is very important to note that control measures should be taken up as early as possible by the concerned authorities. It is necessary to implement all measures carefully considering the potential impacts on the environment and other aquatic lives which will help in saving the life and rejuvenation of Kongba River of Manipur.
(This article is filed under the 4th State Level Media Fellowship Programme on Climate Change under the sponsorship of Directorate of Environment and Climate Change, Government of Manipur.)
