Abstract
The hydrological regime in arid and semi-arid regions is quite sensitive to climate and land cover changes (LCC). The Three-North region (TNR) in China experiences diverse climate conditions, from arid to humid zones. In this region, substantial LCC has occurred over the past decades due to ecological restoration programs and urban expansion. At a regional scale, the hydrological effects of LCC have been demonstrated to be less observable than the effects of climate change, but it is unclear whether or not the effects of LCC may be intensified by future climate conditions. In this study, we employed remote sensing datasets and a macro-scale hydrological modeling to identify the dependence of the future hydrological regime of the TNR on past LCC. The hydrological effects over the period from 2020–2099 were evaluated based on a Representative Concentration Pathway climate scenario. The results indicated that the forest area increased in the northwest (11,691 km2) and the north (69 km2) of China but declined in the northeast (30,042 km2) over the past three decades. Moreover, the urban area has expanded by 1.3% in the TNR. Under the future climate condition, the hydrological regime will be influenced significantly by LCC. Those changes from 1986 to 2015 may alter the future hydrological cycle mainly by promoting runoff (3.24 mm/year) and decreasing evapotranspiration (3.23 mm/year) over the whole region. The spatial distribution of the effects may be extremely uneven: the effects in humid areas would be stronger than those in other areas. Besides, with rising temperatures and precipitation from 2020 to 2099, the LCC may heighten the risk of dryland expansion and flooding more than climate change alone. Despite uncertainties in the datasets and methods, the regional-scale hydrological model provides new insights into the extended impacts of ecological restoration and urbanization on the hydrological regime of the TNR.
Highlights
Global climate has changed dramatically over the past few decades as demonstrated by many studies [1,2,3]
According to the data from Liu et al (2014), we focused on four primary land cover types: forests, grasslands, croplands, and urban areas
There has been a significant change in land cover in the Three-North region (TNR) over the past three decades, primarily due to ecological restoration projects, urban expansion, and industrialization
Summary
Global climate has changed dramatically over the past few decades as demonstrated by many studies [1,2,3]. Due to human activities, land cover has experienced various and rapid changes, especially in recent decades [4,5,6,7]. 2019, 11, 81 affect the hydrological cycle [8,9,10,11,12] regarding water balance and energy balance processes at various scales [13] These changes are more likely to result in serious consequences, such as droughts and floods, in arid and semi-arid regions, where the environment is much more vulnerable than in humid areas [14]. The TNR is an ecologically fragile area, where land degradation has been very serious due to both human activities and changes in natural conditions since the last century, especially in the Northwestern region [15]. In order to solve this problem, the Chinese government has launched a series of ecological restoration programs, beginning in 1978, including the
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