Mechanical beach grooming: A hazard to coastal fauna and flora
Beach dune complexes along with their associated flora and fauna are the most sensitive of all tropical ecosystems of the world. It is for this reason that sandy beaches and dunes of India are categorized as eco-sensitive habitats, under CRZ I, in the CRZ notification of 1991 and 2011. Coastal sand dunes are thus protected by law. Therefore, any unwarranted interference such the use of machines to remove beach litter can result in widespread impacts which may be irreversible.
NIO research reveals that meiofauna of Goan beaches, Candolim in particular, consisted of nematoda (40%), harpacticoida (37%) and turbellaria (23%), and other minor groups. Their concentrations were maximum in April. A Goa University assessment of coastal macrofauna for 7 years yielded 84 new records for the region. Of these, 52 species were found in sandy and muddy habitats. These observations suggest the occurrence of complex and diversified habitats in the coastal regions of Goa.
If Miramar is considered, a large variety of benthic communities inhabit the beach. During three years of sampling at Miramar, NIO results reveal 50 macro benthic species in the intertidal zone. Of these, 15 belong to annelida, 10 to crustacea, 22 to mollusca, and three belong to other groups. Polycahetes were the most dominant group in terms of density and diversity and dominated the low-tide zone, whereas, crustaceans dominated the mid-tide zone. Of these, seven macrobenthic species were identified as keystone species. Removing of a keystone species has an effect much like a keystone in an arch.
It is pertinent to note that of all the intertidal communities on this beach, almost 80% meiobenthic communities and >50% macrobenthic communities inhabit the top 5 cm section of the intertidal zone. Faunal communities in the intertidal area are dominated by burrowing forms such as bivalves, polychates and small crustaceans.
In addition to fauna, around 59 species of dune plants are found in Goa. Dune vegetation plays a crucial role as it is an effective sand binder and hence promotes the stability of dunes and reduces erosive processes. Therefore, mechanical removal of grasses and shrubs from dune fields will lead to elimination of pioneer dune flora resulting in bare dunes. Loose sand gets blown inland with a consequent impact on dune stability. Therefore, mechanical devices are bound to harm the rich benthic life and irreversibly destroy the intertidal communities. Elimination of faunal elements from a beach can create biological deserts. Although beaches need cleaning, only environment friendly manual procedures are to be adopted.
International scientific literature is replete with reports on harmful effects of heavy devices on sandy beaches. A few examples are reviewed below:
(1) The strandline may be ephemeral or permanent accumulation of marine debris on the beach deposited at high tide. Colonised by invertebrates from land and marine ecosystems, strandlines are of great ecological importance, act as precursors to sand dunes, enabling the formation of embryonic dunes and subsequent fore dunes. Heavy machines can obliterate the functions of beach– dune systems.
(2) The total density, species-specific densities and assemblage structure are all significantly influenced by mechanized cleaning on the western Belgian coast. The measurable impacts were an immediate decrease in faunal density and change of assemblage structure.
(3) Human influence on sandy beach biota is illustrated by a decline in abundance and species richness of birds and benthic invertebrates on beaches used by recreational off-road vehicles (ORVs) in California, USA and Queensland, Australia. The ecological consequences include loss of biodiversity, productivity, and critical habitats as well as modifications of the recruitment zone for many sandy beach animals.
(4) Mechanical beach cleaning removes not only all the anthropogenic litter, but also the strandline itself, as well as 10-15 cm of the top sand, effectively destroying the habitats of amphipods and other invertebrates.
(5) Mechanical removal of naturally deposited plant debris has been shown to decrease sandy shore biodiversity dramatically. Cleaned beaches become unattractive to many species that utilize natural strandlines; numbers of shore birds have declined on cleaned beaches of Mediterranean and Baltic sandy beaches.
(6) Beaches that experience the highest amount of trampling had the smallest crab populations on Australia’s Gold Coast. Likewise, the density of ghost crab burrows was significantly higher at the two sites that were least disturbed.
(7) The pilot project at Koksijde, a dune coast of Belgium, demonstrated that the time needed to manually clean 2.1 km of beach was approximately 2 man-days per month. Following the results of the public perception study, there was wide support for manual beach cleaning by 75 per cent of beach users
(8) The Lake Huron Centre for Coastal Conservation, Canada, confirms that mechanized cleaning (a) results in removal of natural organic debris, make sands vulnerable to wind erosion, obliterates beach vegetation, and undermines the beach and dune development; (b) affects dune processes, leads to constricted dunes, has profound negative effects on beach erosion and shore ecology; (c) creates dry sand zones four times wider, macrophyte strand cover was >9 times lower, and native plant abundance and richness were 15 and >3 times lower respectively, significantly increased rates of aeolian sand transport. (9) Latest reports reveal that the city of Cape Town in South Africa is reviewing the way it cleans its beaches because of the potential environmental impact of using mechanical raking equipment. As a result it has cancelled a three-year beach-cleaning contract. The Wildlife and Environment Society of South Africa has advised that beaches should not be mechanically cleaned.
In India, the CRZ notification of 1991 and 2011 explicitly forbids heavy activity on beaches and dunes. Thus, deployment of mechanical devices is tantamount to violation of prevailing CRZ laws. In 2001, a management project for Miramar beach with mechanical removal of beach litter was proposed. Since the harmful effects were imminent, the entire proposal was withdrawn. More importantly, the turtle nesting beaches are in peril as these are endangered species sensitive to vibrations and bright lights. Heavy machines and even vehicles on beaches can prove fatal to these vulnerable marine turtles.
In summary, grooming of beaches alters beach ecology in the following ways: First, the wet sand is drawn up and aerated, contributing to drying out of the sand and making the fine sands vulnerable to wind erosion resulting in sand migration and drifting. Second, grooming can destroy new seedlings establishing at the edge of the dune; this ’embryo’ dune, or pioneer zone, trap wind-blown sand, develops dunes, and continue to stabilize the area. Mechanical grooming hampers these coastal geological processes. Third, the beach ecosystem is a habitat and feeding grounds for wildlife. Heavy machinery can have a detrimental impact on species and habitat.
Therefore, for the sake of conservation, restoration and wellbeing of faunal and floral diversity, mechanized cleaning of sandy beaches should not be allowed under any circumstances. Instead, manual removal of debris by using light hand tools is the preferred alternative.