Dibru-Saikhowa National Park

Two native plant species, Bombax ceiba and Lagerstroemia speciosa, have been found to be behaving like invasive species, altering the natural structure of the park’s riverine ecosystem.

About Dibru-Saikhowa National Park

Location and Geography

Dibru-Saikhowa National Park is located in the Dibrugarh and Tinsukia districts of Assam, in northeast India. It lies in the floodplains of the Brahmaputra River and is surrounded by three rivers:

• North: Brahmaputra and Lohit Rivers

• South: Dibru River

It is one of the most biologically diverse areas in Assam and was designated a UNESCO Biosphere Reserve in 1997 due to its ecological significance.

Climate and Vegetation

The park experiences a tropical monsoon climate, with hot and wet summers and cool, usually dry winters. Its landscape comprises a mix of:

• Moist mixed semi-evergreen forests

• Moist mixed deciduous forests

• Canebrakes (dense thickets of cane)

• Extensive grasslands

Notably, Dibru-Saikhowa contains the largest Salix (willow) swamp forest in north-eastern India, making it ecologically unique.

Flora

Dibru-Saikhowa is rich in plant diversity, including both native and now-problematic species such as:

• Bombax ceiba (Red silk cotton tree)

• Lagerstroemia speciosa (Pride of India)

• Lagerstroemia parviflora

• Dillenia indica

• Bischofia javanica

These native trees are essential components of the forest, but the latest study warns that under altered environmental conditions, even these species may outcompete others, disrupt succession cycles, and reduce plant diversity.

Fauna

The park is a biodiversity hotspot and home to a wide variety of wildlife, including:

• Mammals: Tiger, Elephant, Leopard, Jungle Cat, Himalayan Black Bear, Sloth Bear, Small Indian Civet, Slow Loris, Assamese Macaque, and Squirrels.

• Aquatic Species: Gangetic Dolphin (an endangered species found in the Brahmaputra and its tributaries)

• Unique Feature: Dibru-Saikhowa is the only habitat in India that supports feral (wild) horses.

• Avifauna: Recognized as an Important Bird Area (IBA), it hosts 382+ species of birds, including:

  • Greater Adjutant Stork

  • Lesser Adjutant Stork

  • Greater Crested Grebe

  • White-winged Wood Duck

  • Black-breasted Parrotbill

Current Ecological Concern

Traditionally, invasive species are non-native organisms that spread rapidly, harming the native ecosystem. However, in Dibru-Saikhowa, Bombax ceiba and Lagerstroemia speciosa—both native species—are now altering the riverine landscape in similar ways. Possible reasons for this transformation include:

• Changes in flooding patterns

• Altered sedimentation due to upstream damming

• Climate change and temperature shifts

• Disturbed ecological succession due to anthropogenic activities

Such changes may result in the displacement of native grasses and shrubs, ultimately affecting herbivores and ground-nesting birds, which depend on these specific vegetation types for food and shelter.

Conservation Significance and Challenges

As a UNESCO Biosphere Reserve, Dibru-Saikhowa plays a crucial role in:

• Preserving rare swamp forest ecosystems

• Acting as a natural flood buffer

• Supporting endemism and migratory species

But growing threats include:

• Vegetation imbalance due to aggressive plant species

• Encroachment and grazing

• Pollution from upstream

• Oil exploration activities (earlier controversial attempts were reported)

• Poaching and habitat degradation