Mapping Trajectories of Coastal Land Reclamation in Nine Deltaic Megacities using Google Earth Engine

Sengupta Sengupta,Zilong Zilong,Choi Choi,Banerjee Banerjee,Meadows Meadows,Chen Chen

doi:10.3390/rs11222621

Abstract

Increasing demand for land resources at the coast has exerted immense pressure on vulnerable environments. Population and economic growth in coastal cities have combined to produce a scarcity of suitable space for development, the response to which has frequently been the reclamation of land from the sea, most prominently in China. Urbanization is a key driver of such changes and a detailed investigation of coastal land reclamation at the city scale is required. This study analyzed remote sensing imagery for the period 1990 to 2018 to explore the trajectories of coastal land reclamation in nine major urban agglomerations across the three largest deltas in China using the JRC Global Surface Water (Yearly Water Classification History, v1.1) (GSW) dataset on the Google Earth Engine platform. The results are considered in the context of major national policy reforms over the last three decades. The analysis reveals that total land reclaimed among nine selected cities had exceeded 2800 km2 since 1984, 82% of which occurred after 2000, a year following the enactment of China’s agricultural ‘red line’ policy. Shanghai exhibited the greatest overall area of land extension, followed by Ningbo and Tianjin, especially in the period following the privatization of property rights in 2004. In analyzing annual trends, we identified the developmental stages of a typical coastal reclamation project and how these vary between cities. Scrutiny of the results revealed voids in nighttime light satellite data (2014–2018) in some localities. Although these voids appeared to be characterized by construction, they were occupied by vacant buildings, and were therefore examples of so-called “ghost cities.” In China, as elsewhere, continual land reclamation needs to be considered in relation to, inter alia, sea level rise and land subsidence that pose significant challenges to the vision of sustainable urban development in these three deltaic megacities.

Highlights

The low elevation coastal zone (LECZ) supports 40% of the world’s population, and its limited land resource is subject to immense pressures that are exacerbated by sea level rise [1,2]
Much of the studies on coastal land reclamation have been at a national scale [5,6]; this paper aims to analyze the changing spatial extent of coastal land reclamation in China at the individual city scale, and in relation to evolving urbanization and associated planning policies
Spatial variability in the area of reclaimed land could be observed among the three urban agglomerations; where more than 1800 km2 of land extension occurred around the cities of the Yangtze estuary, followed by Tianjin-Tangshan-Qinhuangdao (925 km2), and the Pearl River agglomeration

Summary

Introduction

The low elevation coastal zone (LECZ) supports 40% of the world’s population, and its limited land resource is subject to immense pressures that are exacerbated by sea level rise [1,2]. The United Nations’ recent report “The Ocean and the Sustainable Development Goals under the 2030 Agenda for Sustainable Development” addresses the land reclamation of salt marshes, intertidal flats, and mangroves as a primary threat to the sustainability of coastal and marine ecosystems [4]. Recent examples of such mega structures at the coast include the Palm resorts of Dubai, international airports in Hong Kong, Macau, and Singapore, mega smart city projects such as ‘Eko Atlantic’ in Lagos, Nigeria, and Songdo smart city, South Korea. The process is deeply rooted in understanding the major policy reforms that China implemented to maximize coastal benefits for its cities and, in turn, help to sustain its national economy

Objectives

Methods

Results

Discussion

Conclusion