文章来源：俞孔坚.沿海景观[J].景观设计学, 2017, 5(4), 4-9.
Coastlines (and coastal zones) are simultaneously the clearest and most uncertain landscapes. In the Old Testament of the Bible, God created the divide between land and sea on the third day, proceeded only after the creation of light and darkness, and firmament:
“And God said, Let the waters under the heaven be gathered together unto one place, and let the dry land appear: and it was so.”
In this origin story the world is divided into two, water gathered for the sea and dry land for land. In China, of the Wu Xing (Five Elements), earth and water are opposites meant to restrain each other. Thus, when they meet in space, the boundary between earth and water is clear; it is the coastline. This unmistakable divide is starkly mapped. For people and many other forms of life, this line is the edge between surviving and perishing.
I had a dream long time ago that I could walk along the coastline with one foot in the water and the other on land, and finally walk over the entire coastline of China, my motherland. I knew this dream was unrealistic: the coastline is ever-changing with the fluctuation of tides, and it is impossible to set foot on the same boundary between water and land twice. The coastline that we understand as a clear boundary through maps is an uncertain transitional zone between sea and land. This line (or belt) can reach a width of a few meters or several kilometers according to its academic definition.
The uncertainty of the coastlines (and coastal zones) is reflected in the changes between water and land. The coastline can change through erosion and sediment deposits, from fossils deposited through volcanic eruption, from alluvial through estuary extension — as is the case with the Yellow River estuary which extends several kilometers to the sea every year. Earthquakes, tsunamis, and other shocks can instantly destroy floodwalls and redefine the area between land and sea. These phenomena make the coastline change unpredictable, as an old saying goes, “With time, seas change into croplands and croplands change into seas.”
Coastlines (and coastal zones) are also the most diverse and fragile landscapes on Earth. They are not the datum through which the opposition of earth and water are measured, but an interwoven zone of reinforcement for the two elements. It is a delicately balanced space reflected in regular changes in water volume, concentrations of salt and nutrients, the flow of wind, and changes in the temperature and rainfall. These variations produce distinctive and rich biocenoses: intertidal mangroves, tidal migrations of shellfish and fish, sea turtles that lay eggs on the land and live in the sea, and seabirds that shuttle between sea and land. These seemingly unpredictable states of neither land nor sea are dynamic processes that are balanced if measured in millions of years. Their subtlety — such as turtles that lay their eggs on the same beaches at the same time every year but adjust their timing based on light and temperature changes — is beyond human imagination.
Coastlines (and coastal zones) are also the most romantic and most dangerous landscapes. I often imagine how the Homo erectus had to leave the dry grassland and head towards the coast, due to the huge impact by climate and environmental changes. Along their way, there were open view of clean and star-bright night, mirror-like waters, flat beach, pleasant temperatures, and plenty of readily-available food. Humans have long shown a preference for the temperate environments of the coastal zone, for which we associated these spaces with the beach, sunshine, and a romancing of the unknown other shore and underwater world. Love, treasure, and longevity are the eternal themes of the sea, from Hans Christian Andersen’s fairytales to the Dragon Palace in Chinese myths. These romantic bubbles are often broken by cruel tragedies. The 2004 Indian Ocean tsunami killed more than two hundred thousand people along a tropical coast, and year after year the loss of life and property brought about by tropical storms is growing.
Today and into the future — due to global climate change — the most cherished qualities of the coastal landscapes are also at risk of being lost. Coastal breakwaters which have mediated the delicate balance of the land and sea are threatened and a large number of environmentally sensitive species have already been destroyed; lives living in the coastal zone also disappear because of sewage, trash, and other waste dumped into the sea; multi-lane expressways made the unpredictable coastal zone once full of imagination become unmistakably boring; and the artificial structures on the beach with a same looking have broken people’s romantic imagination of the coast we desired to experience.
We only have one earth and we only have one coastline. Let us cherish the clarity and uncertainty of the coast, to learn from both its rarity and vulnerability, to treat well its natural resources and diverse creatures, and to let it remain a romantic other shore.