Odisha's Forest Diversity: Physiography, Forest Types, and Ecological Significance

Introduction: The Physiography-Forest Nexus

1. The Northern Plateau (Sundergarh, Keonjhar, Mayurbhanj) - dissected tableland with laterite soils
2. The Central Tableland (Sambalpur, Bolangir, Kalahandi) - rolling uplands of the Mahanadi basin
3. The Eastern Ghats - covering ~36% of the state's land area, with peaks up to 1,672 m
4. The Coastal Plains and Deltas - deltas of Mahanadi, Brahmani, Baitarani, and Subarnarekha

Major Forest Types of Odisha

1. Tropical Moist Deciduous Forests (Northern and Southern)

• Sal (Shorea robusta) is the dominant and most economically important species, forming near-pure stands in the northern districts.
• Associates include Terminalia alata (Asna), Buchanania lanzan (Char), Madhuca indica (Mahua), Anogeissus latifolia (Dhawra), and Diospyros melanoxylon (Kendu/Tendu).
• Understorey species: Lannea coromandelica, Syzygium cumini, and various Ficus species.

• These forests are the primary watershed forests of the Mahanadi, Brahmani, Baitarani, and Subarnarekha river systems - they regulate seasonal stream flows across the Odisha-Jharkhand-Chhattisgarh uplands.
• Simlipal Biosphere Reserve (Tiger Reserve and UNESCO Biosphere since 2009) sits within this zone and harbors tigers, elephants, leopards, and gaur.
• Sal forests support enormous Non-Timber Forest Product (NTFP) production: kendu leaf (used in bidi manufacture), mahua (food and local brew), sal seeds (for sal butter/fat), and char (for cooking oil) - these are the primary livelihood sources for tribal (Adivasi) communities.
• The dense leaf litter of sal forests creates deep humus, maintaining soil organic carbon and nutrient cycling.

2. Tropical Dry Deciduous Forests

• Anogeissus latifolia (Dhawra), Tectona grandis (Teak, especially in southern areas), Hardwickia binata, Boswellia serrata (Salai/frankincense), and Terminalia tomentosa.
• Madhuca indica and Diospyros melanoxylon remain important here.
• Bamboo (Dendrocalamus strictus, Bambusa arundinacea) forms extensive understoreys.

• These forests act as buffer zones between the moist forests of the Eastern Ghats and the degraded scrublands of the semi-arid west.
• Boswellia serrata forests of Kandhamal and Bolangir are a source of shallaki resin used in traditional medicine (Ayurveda).
• Bamboo-dominant patches are critical for the paper/pulp industry and for hundreds of thousands of tribal artisans (bamboo basket weaving, mat making).
• Dry deciduous forests maintain groundwater recharge for the many perennial streams that feed western Odisha's tank irrigation systems.

3. Tropical Semi-Evergreen Forests

• Artocarpus hirsutus (Wild Jack), Mesua ferrea (Ironwood), Michelia spp., Phoebe spp., Litsea spp., and several Terminalia species.
• These are mixed forests where both evergreen and deciduous species share the canopy.

• They represent the transition to evergreen forest conditions and are phytogeographically unique - a meeting point between Eastern Himalayan and Deccan floristic elements.
• These forests harbor a disproportionately high density of endemic plant species (over 3,200 flowering plant species in the Eastern Ghats as a whole).
• They are the primary refugia for wild relatives of crop plants: wild tubers, wild citrus, and wild sugarcane relatives have been documented here, making them critical for agrobiodiversity and food security.
• The moist valley forests are important nesting and foraging habitats for the Giant Squirrel (Ratufa indica), Malabar Pied Hornbill, and several endemic butterfly species.

4. Mangrove Forests (Littoral and Swamp Forests)

• Bhitarkanika (Kendrapara district) - the third largest mangrove tract in India, in the Brahmani-Baitarani delta
• Mahanadi delta (around Paradip)
• Balasore coast (Subarnarekha estuary)

• Avicennia alba, Avicennia officinalis, Rhizophora mucronata, Excoecaria agallocha, Acanthus ilicifolius, Sonneratia apetala, Heritiera fomes
• Associates: Phoenix paludosa, fern Acrostichum aureum, Hibiscus tiliaceus
• Bhitarkanika alone records 73+ mangrove and associate species across 300+ plant species.

• Coastal protection: Mangrove root networks stabilize creek banks, arrest sediment in deltas, and reduce storm surge velocity - communities sheltered by mangroves experienced significantly less damage in the 1999 Super Cyclone and subsequent Phailin (2013) and Fani (2019) cyclones.
• Blue carbon: Mangroves sequester ~24 million metric tons of carbon annually globally; the Bhitarkanika complex contributes meaningfully to India's coastal carbon sinks through above-ground biomass and deep peat/soil organic carbon.
• Faunal richness: Bhitarkanika harbors India's largest wild saltwater crocodile (Crocodylus porosus) population and is a critical nesting ground for Olive Ridley sea turtles at Gahirmatha beach (world's largest mass nesting site). The area was declared a Ramsar Wetland in 2002.
• Fisheries nursery: Mangrove creeks serve as nursery habitats for shrimp, crab (Scylla serrata), and finfish species, directly sustaining coastal fishing livelihoods.

5. Tropical Dry Evergreen Scrub Forests

6. Grasslands, Wetlands, and Savannah Patches

The Physiography-Forest Linkage: A Summary

Broad Ecological Significance of Odisha's Forests

Threats and Conservation Concerns

• Anthropogenic pressures: encroachment, mining (iron ore, bauxite, coal), shifting cultivation (podu), overgrazing, and invasive species (Chromolaena odorata, Lantana camara, Parthenium hysterophorus) are the leading threats.
• The Eastern Ghats face a documented decline in plant diversity due to overexploitation and habitat fragmentation.
• As per ISFR 2023 data, while Odisha is a net gainer, open and degraded forest classes continue to replace dense cover in several districts.
• Odisha's Protected Area network covers only 5.36% of its geographical area (1 National Park - Simlipal; 19 Wildlife Sanctuaries) - a coverage considered below the internationally recommended minimum of 17%.

Conclusion