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Ville et biodiversité



Rebirth of a river in Seoul (Republic of Korea)

In spring 2003, the Mayor of Seoul gave the go-ahead for a Herculean project: the restoration of the Cheonggyecheon stream, which had been completely buried beneath highway infrastructure in the heart of the South Korean capital for over 25 years (1). The figures for this undertaking are mind-boggling: 700,000 workers were mobilized, around 7,200 information meetings organized, over two million plants put in, 21 bridges built, and a linear distance of 5.84 km restored, all for a budget of around €248 million. On 1 October 2005, two years and three months after the work began, the public got their first view of the newly-restored Cheonggyecheon. Today, an average of 50,000 visitors stroll along its banks every day.
Besides the technical achievement, what are the benefits to the population? According to the figures of the public authorities, the results are very satisfactory in this respect as well. Under the combined effect of the water and of the wind generated by the area’s new layout, the temperature at the river site has gone from 2.2 °C warmer than other parts of the city to 0.9 °C cooler. As for air pollution, the concentration of airborne particles has fallen by 15.3%, that of nitrogen dioxide (NO2) by 25.3% and that of BTEX (2) by 25-62%. Ambient noise levels by the waterside have fallen from 73.8 to 62 dB (A) during the day.
And, last but not least, biodiversity has become considerably richer. According to surveys carried out, the number of species living in the area has risen from 98 in 2003 to 788 in 2009. Today, no less than 471 plant species, 245 insect species, 34 species of bird, 27 fish species, 7 species of reptile and amphibian, and 4 species of mammal can be found there. There are even some protected species living on the site, such as the Korean salamander.
Elsewhere in the world, many other urban watercourses are also being restored.


1 - This project was drawn up as part of the long-term green growth policy set up by Lee Myung-bak, President of the Republic of South Korea and the former Mayor of Seoul. 2 - Benzene, toluene, ethylbenzene and m- and p-xylene.

CNRS    sagascience