Spatial-temporal impacts of landscape metrics and uses of land reclamation on coastal water conditions: The case of Macao

•The relationships of land reclamation’s landscape metrics and uses transformation with coastal water conditions are analyzed.•The strength of these relationships depends upon different spatial and temporal scales.•Land reclamation with natural-like shorelines and scientific land uses distribution are recommended. Land reclamation is a common strategy for coastal cities to expand their land territories. Although the marine environment degradation caused by land reclamation has been investigated in numerous studies, further exploration in terms of the spatial–temporal impacts of patterns and uses of reclaimed lands on the coastal environment is required to generate detailed policies for urban planning. Two-thirds of Macao’s territorial space has come from the ocean since the middle of the 19th century. Taking the land reclamation history in Macao from 1975 to 2018 as the empirical case, this study quantifies landscape metrics and uses of reclaimed lands through time, and further explores their impact on coastal water conditions by Granger causality tests, stepwise regression and land use regression across different spatial scales. Results show that landscape metrics have instant effects on the coastal water flow velocity and storm tide fluctuation, while various land uses are related to the coastal water turbidity and quality with a time lag length of two to three years after the land reclamation projects are completed. The strength of the relationship between land uses and coastal water conditions also depends upon spatial scales. The reclaimed land patterns with natural-like shorelines and ecological solutions in proximity to intensive coastal development are recommended to mitigate negative effects on coastal water conditions. Reasonable suggestions for efficient planning and management are provided in the findings that contribute to the environmentally friendly coastal development.