With the increasing number of urban population, human activities have caused high-impact land cover and land use changes (LCLUC) in cities, which give rise to the heatwave, air pollution, waterlogging. However, the systematic technique frame generating spatiotemporal annual urban LCLUC with high resolution remains unsolved.

A research team led by Prof. He Xingyuan from the Northeast Institute of Geography and Agroecology (IGA) of the Chinese Academy of Sciences (CAS) developed a systematic remote sensing frame in Google Earth Engine (GEE), including Landsat pan-sharpening algorithm and the Multilevel Decision Rule (MDR) classifier for the first time. This method applied to generate annual urban LCLU maps of Changchun, China with 15-meter resolution from 2000 to 2019, which supported to quantify the cause and effects of urban LCLUC.

The experiment shows the new method can generate LULC maps with high accuracy for major cities around the world. The MDR classifier and Landsat pan-sharpening algorithm can benefit high spatiotemporal LCLU mapping to GEE users who engage in urban science, remote sensing, and landscape ecology.

It is found that the urbanization of Changchun was uneven before and after the year 2009 during the 21st century: the built-up land expansion halved from rapidly (+2.24 %·yr^-1) to stably (+1.30 %·yr^-1), the cropland loss transited from rapidly (-9.19 %·yr^-1) to slowly (-5.29 %·yr^-1), and the green space increment shifted from rapidly (+2.66 %·yr^-1) to slightly (+0.43 %·yr^-1).

The statistical analysis shows that economic development, population increment, and industrial development are major factors driving LCLUC. The LCLUC is deeply related to the descent of gross agricultural production. The built-up land expansion and the green space growth caused wind velocity descent with the finer particle increment.

The LCLUC information also shows that Changchun was committed to urban greening during the rapid urbanization: the ratio of green space to built-up land stabilized at around 40% in 20 years. It affirmed the government's efforts in the garden city construction. Nevertheless, the significant relationship between LCLUC and finer particles demands the city manager to pay attention to optimize the configuration of urban landscapes.

This study has been published in the Remote Sensing in an article entitled "Recording Urban Land Dynamic and Its Effects during 2000–2019 at 15-m Resolution by Cloud Computing with Landsat Series". It was supported by the Youth Science Fund Project approved by the Youth Innovation Promotion Association of CAS and the National Natural Science Foundation of China.

Contact:

Ren Zhibin

Northeast Institute of Geography and Agroecology

E-mail: renzhibin@iga.ac.cn