Direct and indirect impacts of land use/cover change on urban heat environment: a 15-year panel data study across 365 Chinese cities during summer daytime and nighttime

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Abstract

Context

Land use/cover change (LUCC) can directly and indirectly affect surface urban heat island intensity (SUHII) and the effects need to be decomposed.

Objectives

To perform long-term trend analyses of contribution indexes (CIs) of land use types to urban heat environment in cities and to deconstruct direct and indirect effects of LUCC on SUHII within geographical regions.

Methods

Mann–Kendall test and Sen’s slope were used to examine the trends of CIs and SUHII in 365 cities during summer of 2005–2019. Structural equation models were established to quantify direct and indirect effects of land use types’ CIs on SUHII in six geographical regions of China.

Results

First, SUHII in 78.08% and 73.70% of the Chinese cities increased during summer daytime and nighttime, respectively. Second, the CI of built-up land significantly increased across more than half of the cities in all the six regions. Third, not all land use types exerted both direct and indirect effects on SUHII. At daytime, the CI of cropland (direct) was the dominant factor in East China (1.386), South-central (− 0.637), and Northwest (− 0.399) regions. At nighttime, the CI of water bodies (both direct and indirect) was the dominant factor in Northwest (0.506) and Northeast (0.697) regions while CI of built-up land (both direct and indirect) determined in North China (0.476).

Conclusions

Separation of direct and indirect effects of land use types on SUHII had practical implications for cities to optimize the structures and functions of ecosystems and to take regionally based actions improving the urban heat environment.

Related collections

Most cited references 50

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China and India lead in greening of the world through land-use management

Chi Chen†, Taejin Park, Xuhui Wang … (2019)

Satellite data show increasing leaf area of vegetation due to direct (human land-use management) and indirect factors (climate change, CO2 fertilization, nitrogen deposition, recovery from natural disturbances, etc.). Among these, climate change and CO2 fertilization effect seem to be the dominant drivers. However, recent satellite data (2000–2017) reveal a greening pattern that is strikingly prominent in China and India, and overlapping with croplands world-wide. China alone accounts for 25% of the global net increase in leaf area with only 6.6% of global vegetated area. The greening in China is from forests (42%) and croplands (32%), but in India is mostly from croplands (82%) with minor contribution from forests (4.4%). China is engineering ambitious programs to conserve and expand forests with the goal of mitigating land degradation, air pollution and climate change. Food production in China and India has increased by over 35% since 2000 mostly due to increasing harvested area through multiple cropping facilitated by fertilizer use and surface/ground-water irrigation. Our results indicate that the direct factor is a key driver of the “Greening Earth”, accounting for over a third, and likely more, of the observed net increase in green leaf area. They highlight the need for realistic representation of human land-use practices in Earth system models.