Evolution of soil properties following reclamation in coastal areas: A review

Reclamation in coastal zones is effective for relieving population pressure and ensuring food safety. Since the 1950s, the development of coastal zones has entered a peak period. At present, the reclamation of coastal zones mainly occurs in developing countries. The coastal reclaimed lands are mainly used for agricultural production, urban and industrial development, and port construction. The scale and scope of reclamation in coastal lands are larger than in interior lands, and pose substantial environmental risks. This review summarizes the trends in soil physicochemical property evolution following reclamation in salt marshes from around the world. The following important conclusions were obtained: physicochemical properties of coastal saline soils (CSSs) significantly improved over the long term following reclamation in Eastern Asia. Long term fertilization and cultivation resulted in modified soil structure [an increase in the proportion of macroaggregates (>250 mu m) and silt (0.002-0.05 mm)], enhancing the capacity for preserving fertility and C sequestration. Reclamation significantly increased soil organic matter (SOM), phosphorus (P), and nitrogen (N) concentrations, and soil properties approached a relatively stable level nearly 30 years after reclamation, especially in Eastern Asia. However, in Europe and North America, SOM in coastal reclaimed soils (CRSs) decreased rapidly after reclamation, and soil acidification was also a severe problem during reclamation. Coastal reclamation could significantly increase soil GHG (CO2, CH4, and N2O) emissions, further affecting global C cycle. Microbial biomass and activity as well as activities of related enzymes increased gradually in CRS in Eastern Asia, in particular the activities of urease and phosphatase involved in nutrient cycling. In general, physicochemical properties of CRS in Eastern Asia tend to modify, but deteriorate in Europe and North America. Nevertheless, offshore eutrophication, soil heavy metal and organic pollutant concentrations, and salt marsh ecosystem degradation were the most serious environmental risks posed by coastal reclamation. Some strategies to alleviate these risks are put forward. In this review, we also identified priority areas of future research on CRS. (C) 2014 Elsevier B.V. All rights reserved.