Regulating services can reduce people's exposure to natural hazards such as floods, fire and droughts. The Sundarbans World Heritage Site has been selected to highlight the important benefits that mangrove ecosystems deliver as a result of natural hazard regulation. Inhabiting estuaries and inter-tidal zones, mangroves provide vital ecological stability by delivering protection against erosion, providing buffer zones and reducing flooding– thereby contributing to coastal protection (Colette, 2007; FAO, 2014). It is anticipated that coastal zones, such as the Sundarbans, will become increasingly prone to natural disasters as the results of climate change intensify (Agrawala et al., 2003). Increased exposure to natural hazards amplify the vulnerability of World Heritage Sites by increasing the chances that key ecosystems, listed for having Outstanding Universal Value, will be changed, degraded or destroyed (UNESCO et al., 2010).
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- World Heritage sites can play an important role in mitigating the impacts of natural disasters (World Bank, 2010) through the delivery of regulating services which can reduce people's exposure to natural hazards such as floods, fire and drought (Millennium Ecosystem Assessment, 2005). Sites that conserve areas of mangroves are particularly important for their contribution to coastal protection and flood prevention.
- The increasing frequency of events, such as cyclones and storm surges, as a result of climate change highlights the urgent need to maintain healthy mangrove ecosystems for the continued delivery of benefits that local communities depend on and that contribute to human well-being.
- Evidence suggests that it is more cost effective to invest in risk prevention than to fund post-disaster recovery by preserving the delivery of disaster mitigating ecosystem services rather than attempting to recreate them once an ecosystem's capacity to provide these services has been reduced through degradation (UNESCO et al., 2010).
Location and World Heritage designation
Spanning 10,000km² along the coast of India and Bangladesh, the Sundarbans represent the largest expanse of contiguous mangrove forests in the world (Colette, 2007; Giri et al., 2007; UNEP-WCMC, 2011d). This globally significant ecosystem is situated on the Bay of Bengal, within the delta of the Ganges, Brahmaputra, and Meghna rivers. A network of water courses intersect with a highly variable landscape, including sand bars, mud flats and mangrove islands (UNESCO, 2014i). Sixty percent of the area lies in Bangladesh with the remaining area in India. India's World Heritage site, Sundarbans National Park, was the first to be inscribed in 1987. The Sundarbans Reserved Forest in Bangladesh was also designated a RAMSAR site in 1992 in recognition of its significance as a wetland of international importance (Ramsar, 2013).
Inscribed on the World Heritage List under natural criteria (ix) and (x), the Sundarbans National Park and The Sundarbans represent a wetland ecosystem rich in biodiversity and is the only mangrove ecosystem left in the world to support the Bengal tiger (Panthera tigris tigris). Due to the unique niche their root systems provide, the mangrove forest offers nursery habitats to a wide variety of invertebrate and fish species (Kathiresan & Bingham, 2001). The area is also recognized for supporting important ecological processes, such as delta formation, tidal influence and plant colonization (UNEP-WCMC, 2011d).
Natural hazard regulation
The Sundarbans is situated in a region prone to a high incidence of cyclonic storms. Over the past two centuries the coastal areas and offshore islands of Bangladesh, which the majority of the Sundarbans belongs to, have been affected by 35 severe cyclones and storm surges (Akhand, 2003). In 2007 Cyclone Sidr hit Bangladesh causing the death of almost 3,500 people in Bangladesh and affecting millions of people along the coast (Dept. of Disaster Management - Ministry of Disaster Management and Relief, 2012; Mirza, 2010). According to the IPCC projections, the frequency of dramatic weather events will increase as temperatures and sea levels rise (Dasgupta et al., 2007). Increasing the likelihood of flooding events, the Sundarbans region will become more vulnerable to cyclonic events (Agrawala et al., 2003). The advanced warning system for cyclonic events has improved dramatically in recent years as a result of a government response (Paul, 2009) to Cyclone Gorky, which killed around 140,000 people in 1991. However, there are concerns that rising sea levels will compromise many of the current cyclone shelters (Karim & Mimura, 2008).
Extreme events impact ecological and human systems causing human suffering and economic losses thereby impacting human well-being. The region around the Sundarbans has one of the highest population densities in the world, as a result millions of people living throughout this complex landscape are currently benefiting from the coastal protection provided by these mangrove forests (Giri et al., 2007).
Intact ecosystems are better able to deliver the ecosystem services they provide, such as flood mitigation, and to withstand hazardous events. A study comparing the protection provided by intact and cleared mangrove areas in Belize, found that intact mangrove areas provided more protection from storm events than their degraded counterparts (Granek & Ruttenberg, 2007). In addition, evidence suggests that it is more cost-effective to protect ecosystems that deliver key natural disaster mitigating ecosystem services than to recreate them artificially. The United Nations Development Programme (UNDP) has calculated the costs associated with building 2,200km of coastal embankments in the Sundarbans, which purportedly would provide an equivalent level of protection. It was estimated that US$294 million of capital investment and US$6 million for maintenance each year would be needed; an amount far greater than that currently spent on conserving this essential mangrove ecosystem (Colette, 2007). Consequently, it is more economical to invest in risk prevention, through the preservation of ecosystem services, than to fund post-disaster recovery (UNESCO et al., 2010). Regardless of whether the number and strength of cyclones change as a result of climate change, "exposure of the region to the devastating effects of storms will increase if the mangroves cannot be conserved successfully" (Colette, 2007).