THE National Research & Extension Institute, Mangrove Department is currently monitoring the effects of erosion on coastal mangroves in Regions Three, Four and Six, the research agency said in a release on Tuesday.

The erosion process, which occurs in 20-30 year cycles, is impacting several naturally regenerated and planted restoration sites at Hope Beach, Wellington Park, Greenfield, and several villages along West Coast Demerara.

In the release, NAREI described the coast of Guyana as part of a 1600 km-long muddy coastal system dominated by massive mud banks that migrate from the mouth of the Amazon River to that of the Orinoco in Venezuela.
A study completed by Professors Antony and Gardel in 2013, stated that the dynamics of the Guyana coastline are strongly hinged on pulses of mud abundance or scarcity embedded in multi-year cycles of mud-bank activity and inter-bank phases. Also, that the cyclic mud-bank phases regulate mangrove regeneration by providing a substrate for extremely rapid and large-scale colonisation from older mangrove colonies and vigorous tree growth.

According to Ranata Robertson, Coastal Engineer at the University of Guyana, erosion can be caused by this natural process and by human or man-made interventions. Cited as an example is the building of structures beyond the seawall or within the sea defence area which alters or disrupts the natural movement of sediments, hence, resulting in erosion.

Robertson pointed out that it is important for Guyana to conduct ongoing research to determine the movement of these mud banks and the associated erosion cycle. Also, that studies to the map and model coastline retreat and advance are critical areas of research that needs to be integrated into a long-term coastal zone management programme. Collaborative studies have been ongoing with the University of Guyana Civil Engineering Department, NAREI’s Mangrove Restoration Programme and the Sea & River Defence Division (SRDD) to better understand and model this cyclic process, she added.

Robertson related that mangroves are considered as primary sea defence. The role of coastal mangroves in Guyana is to dissipate or reduce wave energy along the coastline. They not only complement hard coastal defence structures but help with the environmental conservation and cost of maintaining hard structures.

NAREI said while mangroves are subjected to cyclic erosion, studies conducted on Guyana’s coastal mangroves have proven that a mangrove bandwidth of 50 to 80 metres is required to reduce a three-metre-high wave to approximately 0.01metres. In the areas where mangroves are not present, severe over-topping occurs (along Kingston and Sheriff Street), which results in increased cost for maintenance works over a period of time, Robertson added.

According to Kene Moseley, head of NAREI’s Mangrove Department, erosion of the shoreline is a natural process that affects mangrove forests. However, once the forest has adequate width, the mangroves have the potential to naturally restore itself when the cycle changes and there is accretion and deposition of sediments. This natural regeneration is, however, only possible provided that there is no other stress on the system.

The most recent example of the effect of erosion on mangroves was noted along of the West Coast Demerara, Region Three shoreline. NAREI said that it started monitoring the erosion along this stretch of shoreline in 2014 to assess the changing conditions and the impact on the status of the mangrove forest.
Moseley pointed out that during that period the monitoring team had observed and documented extensive rapid erosion along the shoreline. Windsor Forest, Ruimzeight, Rotterdam and Crane were areas regarded as critical. Also, that the erosion had totally cleared mangroves from sections at Windsor forest, while the remaining sections of the forest continued to thin as trees were uprooted.

Last Thursday, NAREI and the SRDD representatives met with the La Jalousie/Nouvelle Flanders Neighbourhood Democratic Council (NDC). The discussion centered on the loss of mangroves within the NDC and the current rip-rap sea defence project being constructed by then Ministry of Public Infrastructure. Moseley presented an overview of the monitoring conducted by NAREI since 2014, and showing the extent of the erosion and impact of the loss of the mangroves.
She noted that the situation was also further impacted by excessive garbage dumping and harvesting of the mangrove trees by fishermen to be used as fishing poles. SRDD District Engineer, Mr. Dennis Ramsingh who briefed the NDC councillors on the status of the rip-rap project, reassured them that the works are being done to reinforce the sea defence due to the loss of the mangroves.

The nature of the works entailed the clearing of the remaining mangroves to facilitate the placement of boulders. NAREI, meanwhile, said it will continue to work with the SRDD to monitor changes in the cycle and elevation along this particular stretch of coastline.
With respect to the other sites, Moseley noted that this is the first time that Hope Beach is experiencing erosion since the mangroves were restored in 2010. Meanwhile at Greenfield, the erosion of the mangrove forest is also being monitored and research is being conducted on the implementation of engineering projects that may reduce the impact of the erosion and save the remaining forest.