The Sundarbans protects us from all kind of disasters. But for how long?
The aftermaths of cyclones Sidr, Aila, Amphan, and many other extreme events, storm surges, riverbank and coastal erosions reminded us that the existence of coastal communities are under vulnerable conditions without a protective greenbelt of mangroves. Fortunately, we have the world’s largest natural mangrove forest, the Sundarbans, safeguarding our climate-vulnerable coastal communities in southwestern coastlines. We also have the world’s largest man-made mangrove forest, the coastal greenbelt, protecting our central and eastern coastlines.
The Sundarbans is a unique gift of nature, but the coastal greenbelt is a marvel of human ecological engineering of coastal afforestation in the world. Being a world leader and pioneer in mangrove afforestation and reforestation, Bangladesh has already planted over 200,000ha of coastal mangrove forest since 1965. Thanks to the Ministry of Environment, Forest and Climate Change, especially Bangladesh Forest Department for creating and maintaining the double wonders of the mangrove world.
These mangrove greenbelts are our first line of coastal defense against a tropical cyclone, storm surge, and riverbank and coastal erosion. First established in 1965-66, a large part of the man-made coastal greenbelt is ageing. Research by Bangladesh Forest Research Institute shows that very little woody vegetation is developing on its own to take over the spots of ageing and naturally dying greenbelt trees. In the Sundarbans, the mangrove forest is developed through a natural ecological succession process where pioneer species (eg, KeoraGewa, etc) are gradually replaced by more woody climax species (eg Sundari). The absence of woody regeneration may result in losing the capacity of the man-made coastal greenbelt in absorbing the shocks of cyclones and storm surges.
Meanwhile, Bangladesh is warming at the rate of 0.05C/year, its sea level is rising by 0.6 to 2 cm/year due to climate change. A severe cyclone is also striking the country in every three years. Without replenishment, the three-year window might be too short for the coastal greenbelt to absorb the first cyclonic strike and being ready for the next. We must enrich the ageing greenbelt, expand the spatial coverage of greenbelts, and thereby establish a next-generation coastal defense before it is too late.
A second line of defense
Firstly, building a second line of defense — conservation and restoration of river and canal-side village mangroves — may turn out to be an effective way to deal with this challenge.
Secondly, about 90% of our coastal greenbelts are only Keora which is less friendly to wildlife and biodiversity. We should diversify our coastal greenbelts and redesign the coastal plantation scheme by including at least eight-10 species of more native eco-system and wildlife-friendly mangrove to make our next-generation coastal forest biologically diverse, wildlife-friendly, and provider of multiple goods and services to the local communities.
Thirdly, we traditionally value our coastal mangrove plantations mainly for their roles in climate change adaptation, giving little attention to climate mitigation benefits. We must overcome this shortcoming and redesign our next-generation coastal plantations in such a way that its adaptation and mitigation values are maximized to make an overall win-win situation. Research has shown that species having larger stature and higher wood density can sequestrate more carbon than species having smaller stature and lower wood density.
Resilience in the long run
In sum, mangrove plantation or restoration schemes aiming to develop our next-generation coastal defense should focus on (1) building a second line of coastal defense by enriching the ageing mangrove plantation, (2) conserving and restoring village mangrove patches and riverside vegetation, and (3) diversifying species composition to create wildlife-friendly plantation.
Most importantly, all mangrove plantations should be raised with species that possess high carbon sequestration and high resilience against climate and natural disasters. These nature-based solutions will help build a formidable coastal defense and enhance our socio-ecological resilience in the long run.
While the Sundarbans and coastal mangrove plantations are currently well-protected and well-managed, village mangrove patches or riverside vegetation remains in the opposite state. Hence, ensuring their sustainable and community-based management is an urgent matter. One underlying problem is that Bangladesh Forest Department does not have jurisdiction over most of the riverside mangrove vegetation. Inter-ministerial and inter-departmental coordination is, therefore, necessary to address the issue. The success of conservation and management of roadside plantation can act as a precedence for planning the conservation of riverside vegetation, especially mangroves.
Acknowledging the UNGA’s declaration of the decade of 2021-2030 as the “Decade on Eco-system Restoration,” the current proposal to enrich the coastal greenbelt or to conserve the riverside village mangroves can be considered as a national priority. In Climate Leaders Summit on April 22, 2021, PM Sheikh Hasina urged planting 30 million saplings nationwide and adopting the “Mujib Climate Prosperity Plan.”
Together, it’s time to envision a formidable next-generation coastal defense against natural disasters by integrating the coastal greenbelt, the Sundarbans, the first line of defense, and the riverside mangroves, the penultimate line of defense. Such a holistic approach would make the life and livelihoods of millions of coastal people safe and secure, thereby leading towards prosperity, sustainability, and socio-ecological resilience — a goal envisioned by Bangladesh Climate Change Strategy and Action Plan, the Bangladesh Delta Plan 2100, and many other plans and policies of Bangladesh government.
Shekhar R Biswas is a Professor of Ecology at East China Normal University, Shanghai; and Arif M Faisal is Program Specialist (Nature, Climate, and Energy) at UNDP Bangladesh. The views expressed in this article are of the authors and do not necessarily reflect those of their employer.