How mangroves in Odisha likely reduced Cyclone Dana’s impact

Sub : Env

Sec: Ecosystem

Context:

Cyclone Dana made landfall near Bhitarkanika National Park and Dhamra Port in Odisha. Although anticipated to cause significant damage, the impact was less severe due to effective measures by state authorities and natural defenses:
- Evacuation Efforts: Over one million people were evacuated to cyclone shelters.
- Mangrove Forests as a Natural Barrier: Bhitarkanika’s dense mangrove cover played a crucial role in reducing the cyclone’s impact.

What are Mangroves?

Mangroves are salt-tolerant trees and shrubs found in estuarine and intertidal zones, where freshwater and saltwater meet.
Characteristics:
- Aerial, breathing roots and waxy, succulent leaves.
- Propagate through seedlings, or propagules, which germinate on the parent tree before dispersing into the water to grow independently.
Largest Mangrove Forest: The Sundarbans, spanning India and Bangladesh, is the world’s largest contiguous mangrove forest.
Types of Mangroves in India: Includes species like Red mangrove, Avicennia marina, and Grey mangrove, Rhizophora.
Locations in India: Notable mangrove forests are found in:
- Godavari-Krishna delta in Andhra Pradesh
- Bhitarkanika in Odisha
- Andaman Islands, Kerala, Gujarat, Tamil Nadu, and others.

How Mangroves Protect Against Cyclones:

Barrier Against Storm Surges: Mangroves block the flow of storm surges (sea-level rises caused by storms) with their roots, husks, and leaves.
Impact on Water Flow:
- According to the World Bank Group, mangrove species like Sonneratia apetala can reduce surge height by 4 cm to 16.5 cm with strips 50 m to 2 km wide.
- Mangroves can also reduce water flow velocity by 29% to 92% with strips 50 m to 100 m wide.
Combined Defense with Infrastructure: Mangroves planted in front of embankments further reduce cyclone impacts by decreasing water flow velocity.

Bhitarkanika’s Mangrove Forest Cover:

Mangrove Area: Odisha has a mangrove forest area of 231 sq km, with Bhitarkanika holding the majority.
- Bhitarkanika ranks second in India after Sundarbans in terms of mangrove density.
- 82 sq km in Bhitarkanika is dense mangrove forest, and 95 sq km is moderately dense.
Wildlife Sanctuary Status: In 1975, a coastal area of 672 sq km was declared the Bhitarkanika Wildlife Sanctuary.
- The core 145 sq km area received National Park status in September 1998.
Cyclone Resilience: Bhitarkanika has withstood multiple cyclones, including the 1999 Super Cyclone, due to its robust mangrove ecosystem.