Wetlands are among the most productive and biologically diverse ecosystems on Earth. They provide many important ecological services, including water purification, flood control, and carbon sequestration. Known as the Kidneys of the earth, the average value of ecosystem services provided by Wetlands is more than 22 Lakh Rupees per hectare, which is more than twice than that of Tropical Forest Ecosystem (as estimated by TEEB – The Economics of Ecosystems and Biodiversity).
Wetlands in India
In India, we have 1,243 wetlands which includes 75 wetlands which are declared as Ramsar Sites. These wetlands support 20% of known Indian biodiversity. But the Wetlands are disappearing three times faster than forests with severe consequences for our future unless urgent action is taken to ensure their survival. Many of India’s wetlands are under severe threat from a variety of factors, and one of these biggest concerns is the harmful effects of invasive alien species.
Invasive alien species in India’s Wetlands
Invasive alien species are non-native plants or animals that have been introduced to an ecosystem and have the potential to cause harm to native species or disrupt ecosystem functioning. The Convention on Biological Diversity (CBD) defines IAS as “an alien species whose introduction and spread threaten ecosystems, habitats, or species with socio-cultural, economic and environmental harm and harm to human health”. According to the National Biodiversity Authority, Out of 169 Invasive alien species in India, 55 are identified in the aquatic ecosystem. These include fishes, plants and microorganisms.
The fishes found under invasive alien species were introduced as food fishes, ornamental fishes, larvicidal fishes, and unauthorized introduction for aquaculture. These fishes heavily affect the survival of native species. For example, recently alien mussel species were found invading Ennore wetlands of Tamil Nadu. Mussels are bivalve molluscs which are consumed as seafood. Eleven of 52 fishing sites in Ennore have been infested by an alien mussel species, wiping out valuable fisher resources like locally prevalent yellow clams (Manja matti) and green mussels (Pachai aazhi).
Some of the common invasive plant species found in Indian wetlands include water hyacinth, alligator weed, common reed, salvinia, and water lettuce.
Water hyacinth
Water hyacinth (Eichhornia crassipes) is a free-floating aquatic plant that is native to South America but has been introduced to many parts of the world, including India. Water hyacinth forms dense mats on the surface of water bodies, blocking out sunlight and reducing oxygen levels in the water. This can lead to a decrease in the growth and survival of native aquatic plants, as well as a decrease in the populations of fish and other aquatic animals. Water hyacinth can also interfere with boating and fishing activities, which can have economic impacts on local communities that rely on these activities for their livelihoods.
Alligator weed
Alligator weed (Alternanthera philoxeroides) can grow to a maximum height of two meters. Its dense mats block light from penetrating water bodies and it can inhibit native aquatic plants from growing. In addition, it can interrupt water flow and possibly cause flooding in nearby areas. Alligator weeds are also causing significant threat to human health by providing ideal habitats for mosquito larvae, resulting in heightened risks of mosquito-borne diseases. To control the growth of alligator weed, herbicides like liquid glyphosate formulations have been effective on alligator weed above the water line, but ineffective on plants in the water.
The Common reed
The common reed (Phragmites australis) is a tall, perennial grass that can grow up to five meters in height. It can form dense stands that outcompete native vegetation, leading to a loss of biodiversity. In addition, common reed can alter hydrology and sedimentation patterns in wetlands, which can have negative impacts on water quality.
Overall implications for Wetlands
Hence we can summarize the implications of various invasive alien species of plants and fishes in India from ecological and economical perspectives. From ecological point of view, these species can alter natural hydrology of wetlands by changing the way water flow through them, they can disrupt the nutrient cycle by outcompeting native species for resources, and can alter the food web by wither outcompeting native species or by providing a new food source for predators.
Invasive alien species like water hyacinth which are highly flammable can also increase risk of wildfires. Eventually all of these ecological impacts lead to loss and biodiversity. Economically, managing and controlling invasive alien species can be expensive and challenging, and it requires ongoing efforts to prevent their spread and minimize their impact on wetland ecosystems. The loss of various services provided by wetlands, including water storage, groundwater recharge, flood control, and climate regulation, can have significant socio-economic implications heavily affecting local communities that rely on wetlands for their livelihoods, food, and water security.
Available solutions
As we can see that the invasive alien species can have very far fetching impacts on wetlands, biodiversity and humans which makes it very clear how crucial it is to control and manage the invasive alien species from wetlands. Some of the ways to deal with these alien species include the use of mechanical and chemical control methods, as well as biological control using natural enemies of the invasive species.
For example, water hyacinth weevils (Neochetina spp.) have been introduced to Indian wetlands as a biological control agent for water hyacinth. These weevils feed on water hyacinth and can reduce its growth and spread. However, the use of these control methods can also have unintended consequences, and hence more research is needed before applying them on a large scale.
Preventing the introduction of invasive alien species in the first place is the best approach to managing them in wetland ecosystems. Measures such as regulation of the trade in live aquatic organisms, screening of imported plant material, and public education and awareness-raising campaigns can help to prevent the spread of invasive alien species in Indian wetlands. In addition, monitoring and early detection of new invasive species is important and very crucial to prevent their establishment and spread.
Conclusion
The impacts of invasive alien species on wetlands in India are significant and pose a threat to the health and functionality of these critical ecosystems. Addressing this problem will require a concerted effort from all stakeholders, including government agencies, NGOs, and local communities. By working together to prevent the introduction and spread of invasive species, and implementing effective management strategies, we can help to preserve and protect the valuable ecological services provided by wetlands, and ensure their continued use and enjoyment by future generations.
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Written by: Ram Dayal Vaishnav