Dear Editor,

The matter is too serious to be argued without conviction. Enlightenment must be secured through discernible research and the keen observations of residents, whether or not technically trained. I am referring to the reports in your newspaper concerning the effectiveness of cultivation of mangrove as a means of protection of sea defence dams and structures against wave action and erosion by the sea. I have studied the remarks of the acting Chief Sea and River Defence Officer (SN, 28.1.10), the reported statements of Mr Charles Sohan, a professional engineer (SN, 25.1.10) and the remarks by some ministers and residents of areas where experimental work on mangrove cultivation was done. (SN, 25.1.10).

Now it is proposed to enact new legislation to protect mangrove cultivated on the foreshore, even though the existing Sea Defence Act seems to provide adequate protection against interference from unauthorized persons, and clearly prohibits removal of any material from the foreshore without permission. But perhaps the birth of LCDS has accorded a new but questionable status to the lowly mangrove of Guyana. It has been cultivated in several islands in the Pacific and even in Barbados, I understand, with reasonably good results as a barrier against wave action. But Guyana’s conditions are unique and must be studied to be understood. I do not intend to criticize anyone’s opinion nor will I be the champion for anyone. I will simply state the facts as I know them from my association with sea defences as an engineer and consultant during the period 1954 to the present.

Mangrove and courida bush grew on the foreshores in many parts of the coast and have been doing so from time immemorial. They were not cultivated and naturally gave an option for reducing the effect of wave action on any kind of sea defence. Their presence was respected and valued but their growth was unpredictable and seemed to appear and disappear mysteriously. At times it was detected that the courida was willfully cut down to serve as fuel for burnt earth heaps and mangrove for other uses. The sea defence rangers were authorized to prosecute under the law until the offence ceased. In fact the rangers were also authorized to remove and impound cattle which destroyed the plants and shoot pigs which also interfered. This latter practice was popular at Christmas time and served as a bonus to some rangers. Mangrove and courida were protected but still disappeared in some places and re-appeared in others.

The mystery of the appearance and disappearance of the mangrove was actually solved by Mr JB Manson-Hing in the 1960s after the departure of the team from the Delft Hydraulics Laboratory who had submitted their report entitled ‘Demerara Coastal Investigation (Coastal Erosion in British Guiana)’ in 1962. I was acting Chief Works and Hydraulics Officer at the time and JB Manson-Hing was the Executive Engineer, Sea Defences, ably assisted by his two hydrographic surveyors, Sammy Luck and Paul Kranenburg who were schooled in some of the techniques used by the Delft Hydraulics team.

The Dutch team established that there was a pattern of erosion and accretion occasioned by the drift of shoals of sling mud along the Guyana coast. These shoals originated at the mouth of the Amazon and petered out at the Orinoco. In summary, they wrote: “Protective mud banks shift along the Guyana coast from east to west at an approximate speed of propagation of ¾ statute mile per year. Areas of erosion occur in between these shoals shifting equally, and exposing every section of the sea wall periodically about three times a century. Careful extrapolation of sounding data makes it possible to predict years in advance the places where erosion will occur.”

The trio of Manson-Hing, Luck and Kranenburg were able to map the extent and passage of the mud shoals, but they went one step further in observing that mangrove and courida were still removed when the erosion cycle reached their location but tended to re-appear in those areas of foreshore subjected to the accretion cycle. Indeed, this fact was used to indicate when the sea defence wall or dam was likely to be safe or critical and a maintenance plan was devised accordingly and used quite successfully thereafter. The accretion zone provided sufficient protection for new construction and maintenance to proceed, while the erosion zone had to be carefully monitored until they became accretion zones where work could be economically undertaken, if necessary. Mangrove and courida were totally removed when the erosion cycle reached them. Their protective value was lost.

For some inscrutable reason this policy was allowed to lapse with the departure from office of those persons who implemented it. They retired or emigrated and the records disappeared.

The present excitement about mangrove cultivation was probably derived from the work of the Dutch consultants Royal Haskoning which was financed by the European Union and who worked in collaboration with the Sea Defence Division of the Ministry of Works and Communications on a project entitled ‘Institution Capacity Building on Guyana Sea Defences.’ However, they did not appear to have completed their work for they had not re-identified the location of mud shoals and the areas of erosion as they might have existed in 2006 when their reports were finished. It would be useful to all to get more information more precisely so as to interpret the timing of the propagation of the mud shoals and consequently the likely zones of erosion.

It is unlikely that the forces of Nature would insensibly blend with the dictates of the new legislation and allow the foreshores of Guyana to be blanketed at will with mangrove vegetation.

Yours faithfully,
Philip Allsopp