Invasive Species Threatens the Fringe Ecosystem of Amchang Wildlife Sanctuary
Text by Avishek Sarkar
View of Amchang Wildlife Sanctuary
Photo: Kukil Gogoi
The city of Guwahati is the gateway to North-East India, and the geographical location plays a huge role in the population dynamics as well as land use/cover change in and around the city. The urban sprawl has evidenced a persistent increase, with a rise in settlements towards the forests that surround the city from East, West and South, while being restricted to some extent by river Brahmaputra towards the North. Towards the West, Rani-Garbhanga Reserve Forest and Deepor Beel Wildlife Sanctuary (only the other Ramsar Site of North-East India along with Loktak Lake of Manipur) marks the boundary of the city, with the forests of Meghalaya towards South and Amchang Wildlife Sanctuary (AWLS) towards the East.
The city in itself is spread across only 216 sq km (area under Guwahati Municipal Corporation), most of which is covered by built-up areas. This is the reason people are moving towards the forests and hills around the protected areas. All the protected areas around Guwahati are facing high pressure due to the changes incurred around and within them by the anthropogenic disturbances. These forests are home to rich biodiversity and a part of the Indo-Tibetan biodiversity hotspot. There is an increasing pressure on their habitats as well as the corridors that are important for their movement. The Amchang Wildlife Sanctuary is an integral part of this landscape, regulating the micro-climate of the eastern parts of Guwahati city.
Map courtesy: Geo-spatial Technology & Application Division, Aaranyak
AWLS is spread across an area of 78.64 sq km (from 26013’E to 26009’E and 91, bounded by Guwahati city towards West, Brahmaputra towards North, Meghalaya towards South and agriculture-plantation patches towards the East. It was notified in the year 2004, to help conserve the Elephant populations dependent on the forest landscape. The sanctuary was constituted by integrating three reserve forests, viz., Khanapara, Bonda and Amchang Reserve Forest. Diverse fauna of Amchang includes 44 mammalian species, 52 reptiles, 76 butterflies, 15 amphibians and over 250 bird species. Semi-evergreen and moist-deciduous are the vegetation types found within the sanctuary. Mostly covered by moderately dense forests, the open forests are increasing with numerous wetlands spread across the area, that acts as the water source for communities living around the sanctuary.
Glimpses of Amchang Wildlife Sanctuary
Credit: ecoNE team
In addition to the utilitarian values (timber, fodder, ethno-medicine etc.), the landscape is a source of many other ecosystem services (regulating, cultural as well as a plethora of supporting services). But with increased anthropogenic pressure on the forests, there is a risk of declining ecosystem services. The unchecked establishment and expansion of urban sprawl as well as industrial development in the landscape has resulted in posing a threat to the native biodiversity.
The forest department, in lieu of these threats, conducted an eviction drive in the year 2017 to check the increased illegal settlement within the sanctuary area. In addition to the recurrent eviction drives, the other issue that has been bringing AWLS into the spotlight in recent times is the increase in man-elephant conflict. Instances of the wild elephants wandering to settlement areas have been on the rise, causing damage to life and property of the local people.
The increased pressure on ecosystem functions and the biodiversity is facing Habitat fragmentation and Invasion by alien species. Anthropogenic actions are a precursor to both these pressures. The forest edges are the most vulnerable part of a forest ecosystem, facing maximum pressure and undergoing maximum degradation. The edges thus act like an indicator of all the different threats faced by any particular ecosystem.
Like other ecological threats, the spread of invasive species also, start from the forest edges. The study of invasive species and their distribution is very important, since they play a major role by out-competing native species occurring within the same niche. Protected areas across the globe have been facing the threat due to invasive species, with the stakeholders trying location specific intervention methods to mitigate their impact. Other major protected areas of the state, such as Kaziranga and Manas National Park also have been facing immense threat from invasive flora, with the likes of Mimosa diplotricha, Lantana camara, Parthenium hysterophorus etc. The major invasive flora occurring within and around AWLS are- Mikania micrantha (Assamese name- Japani lota), Ageratum conizoides, Lantana camara, Chromolaena odorata, Parthenium hysterophorus and Mimosa diplotricha. Eichhornia crassipes is found at most of the wetlands across the sanctuary.
Mikania micrantha is the most widely spread of the lot, covering all the open forests and open areas, in addition to the moderately dense forests as well. Being a climber, the bright green leaves of this species can be seen covering trees, shrubs, herbs and grasses likewise. It is a very fast-growing species, and thus is a major threat to the native species, covering areas that otherwise would have been covered by native flora. L. camara is a shrub with beautifully coloured flowers, spread across the edges and paths made by local people for forest products extraction or by forest staff for patrolling. Other species are also very recurrent across the landscape, making up the understory vegetation of the Open forests and Open areas likewise. On the other hand, the wetlands have been facing threat by E. crassipes, since it covers the water surface and blocks the sunlight, making it difficult for the aquatic life to flourish.
The distribution of these invasive species is minimum at the areas with dense canopy, since the canopy hinders these sun-loving invasive. The management of this forest landscape thus calls for a multi-faceted approach. In addition to employing eradication techniques for these invasive species, the forest cover also needs to be improved using diverse native trees as well as checked movement of people within the protected area and decreased infrastructure development within the Eco-sensitive zone of the sanctuary. With a comprehensive approach of the forest staff, working with the local people, stakeholders and environmentalists, the health of this deteriorating ecosystem can be restored.
About the Author:
Avishek Sarkar, a Research Scholar from FRI Dehradun is pursuing his PhD in Forest Ecology and Climate Change. Currently working with Aaranyak, he specializes in Wildlife Ecology and Remote Sensing-GIS.
You can reach him at firstname.lastname@example.org