Whither coastal ecosystem research

Whither Coastal Ecosystem Research: Management of Salt Affected Soils sans Factors Threatening the Ecosystem Loses Significance

H.S.Sen and Dipankar Ghorai

Excerpts from the presentation made in the National Symposium on “Salt-affected Soils” during the 75th Annual Convention of Indian Society of Soil Science, held at IISS, Bhopal on 12-15 November, 2010

According to World Resources Institute coastal areas may be commonly defined as the interface or transition areas between land and sea, including large inland lakes. Coastal areas are diverse in function and form, dynamic, and do not lend themselves well to definition by strict spatial boundaries. Unlike watersheds, there are no exact natural boundaries that unambiguously delineate coastal areas at the global or national scale. According to them, the world coastline extends from 350,000-1,000,000 km in length, depending upon how finely the ‘length’ is resolved. More comprehensively, the coastal ecosystem has been defined by the blogger as representing the transition from terrestrial to marine influences and vice versa. It comprises not only shoreline ecosystems, but also the upland watersheds draining into coastal waters, and the nearshore sub-littoral ecosystems influenced by land-based activities. Soil salinity per se in the coastal ecosystem does not have much significance as far as productivity of crops on these soils is concerned, unlike any other ecosystem, unless it is considered in association with other relevant ecological factors threatening its very stability. According to an estimate 51 percent of the world’s coastal ecosystems appear to be at significant risk of degradation from development related activities.
Of the two coastlines in India length of the East coast is higher than that of the West. The continental shelf is more stable than the coast. The continental shelf of 0-50 m depth spreads over 1,91,972 sq km and between 0-200 depth over 4,52,060 sq km. The shelf is wide (50-340 m) along the East coast. The Exclusive Economic Zone is estimated at 2.02 million sq km.
Practically no systematic study was earlier made in India to demarcate the coastal soils based on well-defined scientific indices. Notable among the past works, however, was that of an earliest one by CSSRI as 3.1 million hectare area (including mangrove forests), while another as high as 23.8 million hectare under coastal salinity in India. The coastal saline soil has been referred by various workers almost synonymously with coastal soil which is not correct since all coastal soils are not saline in nature. None of the above estimates appears to have been made on sound scientific basis. However, the latest compilation made by NBSS&LUP on the soil resources and their potentials for different Agro-ecological Sub Regions (AESR) in coastal tracts of India show total 10.78 million hectare area under this ecosystem (including the islands), which was the first scientific approach for delineation of the coastal ecosystem.
Different factors limiting agricultural productivity in the coastal plains are listed as (1) Excess accumulation of soluble salts and alkalinity in soil, (2) Pre-dominance of acid sulphate soils, (3) Toxicity and deficiency of nutrients in soils, (4) Intrusion of seawater into coastal aquifers, (5) Shallow depth to underground water table rich in salts, (6) Periodic inundation of soil surface by the tidal water vis-à-vis climatic disaster and their influence on soil properties, (7) Heavy soil texture and poor infiltrability of soil causing frequent drainage congestion, (8) Limited availability of good quality water for irrigation, (9) High population density, etc.
Management of salt affected soils, based on the constraints cited above, through only soil, water and crop management catches immediate attention of all concerned for augmenting productivity in the coastal ecosystem. What is of paramount importance to note, though most often ignored, that the damage to the coastal ecology, besides the above, is continually being caused by countless other ill-planned anthropological activities resulting in eutrophication, hypoxia & nutrient imbalance, erosion & sedimentation of soil, and under-sea tectonic movement, and all these are compounded manifold by increasing incidence of natural disasters owing to global warming. Measures need to be undertaken on off-shore and on-shore protection measures against the damages thus likely to be caused. It is therefore mandatory to give a holistic look to the interaction matrix of all these factors cited above, and not the management of the salt affected soils alone, to ensure lasting stability of the ecosystem.