Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Ecosystems and Climate
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Hydrometeorology
- Part IV Biometeorology
- Part V Terrestrial Plant Ecology
- Part VI Terrestrial Forcings and Feedbacks
- 25 Terrestrial Ecosystems and Earth System Models
- 26 Seasonal-to-Interannual Variability
- 27 Biogeophysical Climate–Vegetation Dynamics
- 28 Anthropogenic Land Use and Land-Cover Change
- 29 Carbon Cycle–Climate Feedbacks
- 30 Nitrogen, Chemistry, and Climate
- 31 Aerosols, Chemistry, and Climate
- 32 Urbanization
- 33 Climate Intervention and Geoengineering
- 34 Coevolution of Climate and Life
- Appendix
- Index
- Plate section
- References
28 - Anthropogenic Land Use and Land-Cover Change
from Part VI - Terrestrial Forcings and Feedbacks
Published online by Cambridge University Press: 05 November 2015
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Ecosystems and Climate
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Hydrometeorology
- Part IV Biometeorology
- Part V Terrestrial Plant Ecology
- Part VI Terrestrial Forcings and Feedbacks
- 25 Terrestrial Ecosystems and Earth System Models
- 26 Seasonal-to-Interannual Variability
- 27 Biogeophysical Climate–Vegetation Dynamics
- 28 Anthropogenic Land Use and Land-Cover Change
- 29 Carbon Cycle–Climate Feedbacks
- 30 Nitrogen, Chemistry, and Climate
- 31 Aerosols, Chemistry, and Climate
- 32 Urbanization
- 33 Climate Intervention and Geoengineering
- 34 Coevolution of Climate and Life
- Appendix
- Index
- Plate section
- References
Summary
Chapter Summary
Changes in land cover and in human uses of land can influence climate. Conversion of forests and grasslands to agricultural land alters net radiation, the partitioning of this energy into sensible and latent heat, and the partitioning of precipitation into soil water, evapotranspiration, and runoff. Among the surface characteristics altered by land-cover change are albedo, surface roughness, leaf area index, canopy conductance, root depth, and soil texture and structure. Land degradation in arid and semiarid climates increases surface albedo, reduces evapotranspiration, and may contribute to low rainfall in these regions. Extensive deforestation and land clearing have altered the climate of vast regions of Australia. Clearing of tropical forests for pastures creates a warmer, drier climate. Clearing of temperate forests and grasslands to cultivate crops cools climate, primarily because of higher albedo. However, the climate signal associated with crops is complicated and is related to the timing of crop planting, maturation, and harvesting relative to the phenology of natural vegetation. Irrigation leads to a cooler, moister climate. The influence of historical land-cover change on climate needs to be considered as a climate forcing in addition to traditional forcings such as greenhouse gases, aerosols, solar variability, and ozone. Climate model simulations show that the biogeophysical effects of historical land-cover change have cooled climate over large regions of North America and Eurasia. This biogeophysical cooling is comparable to, but of opposite sign, greenhouse gas warming over the same period. This cooling primarily results from increases in surface albedo with deforestation. Conversions among forests, pastureland, and cropland are thought to have decreased annual evapotranspiration. The net effect of anthropogenic land use and land-cover change is the balance between these biogeophysical changes and carbon emission from land use.
Green Planets and Brown Planets
Much of the natural vegetation of the world has been converted to cropland and rangeland (Figure 2.8). Human uses of land such as cultivation, grazing, forest clearing, and forest regrowth on abandoned farmland alter net radiation, the partitioning of this available energy between sensible and latent heat, and the partitioning of precipitation into runoff and evapotranspiration. These changes occur from modifications of albedo, surface roughness, leaf area index, rooting depth, and canopy conductance and also from changes in soil texture and structure that affect soil water. Soil texture determines how much water is available for evapotranspiration.
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- Information
- Ecological ClimatologyConcepts and Applications, pp. 523 - 562Publisher: Cambridge University PressPrint publication year: 2015