Impact of human activities on the health of ecosystems in the changjiang delta region

Most of the world mega-cities are located within the distance of 100-200 km from the coast, and the delta region is the place where the modern civilization developed in human history. In the mainland of China, the eleven provinces in the coastal region represents ca. 15 % of the national land surface area, but sustain 40 % of national population with 60 % of total GDP. Coastal environment represents one of the most dynamic habitats on the earth, i.e. land-ocean interface, and supports some of the most diverse and productive ecosystems (LOICZ: www.loicz.org). Vulnerable coast environments have been disturbed by anthropogenic activities, particularly owing to the rapid industrialization and urbanization in the 20^th Century (Kim et al., 1999; Bouloubassi et al., 2001). Land-based activities over the drainage basin (i.e. land clearing, damming, harbor construction and land reclamation) have a profound impact on the coastal environment by changing the fluvial fluxes of water and sediments, perturbation by navigation and engineering construction (e.g. tunnel and bridge), and loss of delta habitat, for example, the Changjiang (Zhang et al., 1999). Moreover, the projected future climate changes will affect the physical, sedimentary and ecological processes in coastal environment, which can be considered an added stress on already overstressed ecosystems; this will further reduce the ability of coastal systems to provide goods and services. For instance, the loss of habitat by coastal erosion, changes in biogeochemical processes by altering nutrient fluxes, and shifts in adjacent marine biological community structure by pollution as well as overfishing, have all been identified as major, on-going impacts. Their occurrence, particularly in areas where rapid economic innovation and population growth take place like China, can be severe (World Resources Institute: www.wri.org). (figure presented) Prolonged and intensive use of inorganic fertilizer in agriculture, changes in land use patterns, deforestation, and discharge of industrial and municipal wastes have all contributed to the eutrophication of coastal waters on a global scale. The estuarine and coastal regions showing such degradation include the North Sea, Baltic Sea, Adriatic Sea, and North America (De Jonge et al., 1994; Richardson and Heilmann, 1995). Over last 50 years, flux of natural and synthetic materials from the terrestrial sources to the coastal environment has increased by 1.5-2 folds (Meybeck & Ragu, 1995). Salt marshes are an important sink for nutrients and anthropogenic substances, such as heavy metals in the continuum from land to the ocean (Gambrell, 1994; Callaway et al., 1998; Olivie-Lauquet et al., 2001). The impact of heavy metals and synthetic organic pollutants discharged into salt marshes can be substantial and have potential threat to the health of aquatic food-web (Turner, 1990; Wright & Mason, 1999). Pollutants (e.g. heavy metals) accumulated in the coastal sediments can be remobilized and removed to the deep-water area, impacting on the health of ecosystems (Cundy et al., 1997). Requirement for the protection of coastal environment has promoted the monitoring of pollutants in anthropogenically disturbed ecosystems, particularly harbours and delta regions (Wises et al., 1995; Wright & Mason, 1999; Olivie-Lauquet et al., 2001). In this study, the status of the Changjiang (Yangtze River) Delta Region is examined (Figure 1). The emphasis is given to the anthropogenic impact on the health of the ecosystem in the delta and adjacent coastal waters, along with the progress of urbanization of Shanghai.