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Chapter 1 Scientific Basis of Global Climate Change

5. Land Surface Processes

Land surface processes are an indispensable part of the Earth’s climate system, involv-
ing various physical, chemical, and biological processes. These processes not only shape
the morphology and characteristics of the Earth’s surface but also exert profound impacts
on global climate through interactions with the atmosphere, hydrosphere, and ecosystems.
Changes in land surfaces, such as vegetation cover alteration, soil moisture variation, and
urbanization progress, can directly or indirectly influence the climate system. Furthermore,
changes in land use patterns, including deforestation, agricultural expansion, and urban
sprawl, have intensified the potential climate impacts of land surface processes.
(I) Impact of Vegetation Cover
Vegetation cover is one of the most critical features of land surfaces, exerting multiple
influences on the climate system.
First, vegetation absorbs carbon dioxide through photosynthesis and releases oxygen,
thereby regulating greenhouse gas concentrations in the atmosphere. Dense vegetation areas
such as forestsact as carbon sinksan essential component, capable of absorbing substantial
amounts of carbon dioxide to slow the rate of global warming. However, deforestation and
land degradation reduce vegetation cover, leading tocarbon sequestration capacitydecline,
thereby exacerbating the greenhouse effect.
Secondly, vegetation influences surface energy balance and water cycle through tran-
spiration. Plants release moisture into the atmosphere through their leaves, increasing air
humidity, lowering surface temperatures, and promoting cloud formation and precipitation.
This process plays a vital role in regulating regional climate and water distribution. For in-
stance, tropical rainforests maintain high precipitation levels through transpiration, while
reduced vegetation in arid areas may lead to decreased rainfall and drier climates.
(2) Changes in Soil Moisture
Soil moisture is another critical factor in terrestrial surface processes, directly influ-
encing surface energy balance and the water cycle. Water in the soil enters the atmosphere
through evaporation and transpiration, affecting air humidity and precipitation patterns.
Changes in soil moisture also impact surface albedo, as moist soil typically exhibits lower
albedo, absorbing more solar radiation and consequently increasing surface temperature.
Furthermore, soil moisture significantly affects ecosystem health and functionality.
Moist soil facilitates plant growth and microbial activity, promoting carbon sequestration
and cycling. However, arid or excessively wet soil conditions may lead to vegetation degra-
dation, soil erosion, and declining ecosystem functions, ultimately affecting regional climate.
(3) Climatic Effects of Urbanization
Urbanization is a significant feature of modern societal development, but its impacts on
climate systems cannot be overlooked. Urban areas typically contain high-density buildings,
roads, and populations, giving rise to the “urban heat island effect.” This phenomenon refers
to urban regions exhibiting markedly higher temperatures than surrounding rural areas due to

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