1. Changes and Feedbacks of Land-use and Land-cover under Global Change Mingjie Shi Physical Climatology Course, 387H The University of Texas at Austin, Austin, TX November 25, 2008

2. Outline 1. Introduction of land-use and land- cover change. 2. Changes of forests and their feedbacks 3. Changes of tropical savanna and their feedbacks 4. Discussion

3. 1. Introduction of land-use and land-cover change Variations promoted by anthropogenic activities include: Variations promoted by anthropogenic activities include:  Substituting forests and grassland for agriculture use,  Intensifying farmland production,  Urbanization.

4. Deforestation Intensified use Urbanization

5. Land-use and land-cover change surface energy and water balance Albedo Roughness length Leaf-area index (LAI )

6. 1. Introduction of land-use and land-cover change Research methods: Research methods:  Climate models (general circulation model (GCM)),  Remote sensing,  Field study results.

7. Outline 1. Introduction of land-use and land- cover change. 2. Changes of forests and their feedbacks 3. Changes of tropical savanna and their feedbacks 4. Discussion

8. 2 Changes of forests and their feedbacks 2.1 Tropical forest 2.2 Temperate forest 2.3 Boreal forest

9. 2.1 Tropical forest Climate model simulations show that tropical forests maintain high rates of evapo- transpiration, decrease surface air temperature, and increase precipitation compared with pastureland. Flux tower measurements in the Brazilian Amazon indicates that forests have lower albedo compared with pasture.

10. 2.1 Tropical forest Simulations with general circulation models (GCMs) demonstrated that changes in albedo, roughness length, leaf-area index and rooting depth caused by tropical deforestation reduce precipitation and relative humidity and increase surface temperature and wind speed. Simulations with general circulation models (GCMs) demonstrated that changes in albedo, roughness length, leaf-area index and rooting depth caused by tropical deforestation reduce precipitation and relative humidity and increase surface temperature and wind speed.

11. 2.1 Tropical forest Greater insolation at the soil surface Increases the air temperature and decreases relative humidity near the soil surface. Increase fire risk Reduces tree cover and prevents tree regeneration Thinning or removal of the forest canopy

12. 2 Changes of forests and their feedbacks 2.1 Tropical forest 2.2 Temperate forest 2.3 Boreal forest

13. 2.2 Temperate forest Temperate forests are forest in the temperate climate zones. They include: Temperate forests are forest in the temperate climate zones. They include:  Temperate deciduous forest,  Tempereate broadleaf and mixed forests,  Temperate coniferous forests,  Temperate rain forest.

14. 2.2 Temperate forest Studies of eastern United States forests: trees maintain a warmer summer climate compared with crops. Lower albedo, augmentation of evaporative cooling from crops and feedbacks with the atmosphere that affect clouds and precipitation. Mesoscale model simulations in the United States in July indicated: trees increase evapotranspiration and decrease surface air temperature compared with crops. Flux tower analyses show: conifer and deciduous broadleaf forests in North Carolina have lower surface radiative temperature than grass fields. Greater aerodynamic conductance and evaporative cooling. In western Europe, forest and agricultural land have comparable surface radiative temperature when soil is moist but respond differently to drought..

15. 2.2 Temperate forest It can be seen that the net climate forcing of temperate forests is highly uncertain. Besides, the future of temperate forests and their climate services has high uncertainty. It can be seen that the net climate forcing of temperate forests is highly uncertain. Besides, the future of temperate forests and their climate services has high uncertainty.

16. 2 Changes of forests and their feedbacks 2.1 Tropical forest 2.2 Temperate forest 2.3 Boreal forest

18. Boreal forests are different in energy balance, which usually based on the types of forest.Boreal forests are different in energy balance, which usually based on the types of forest. Conifer forests, for example, have low summertime evaporative fraction (defined as the ratio of latent heat flux to available energy), while the deciduous broadleaf forests always produce high rates of sensible heat exchange and deep atmospheric boundary layers.Conifer forests, for example, have low summertime evaporative fraction (defined as the ratio of latent heat flux to available energy), while the deciduous broadleaf forests always produce high rates of sensible heat exchange and deep atmospheric boundary layers.

19. 2.3 Boreal forest Climate forcing raises the fire frequency Surface albedo increase (The trend of temperature decrease) Carbon emission increase (The trend of temperature increasae) offset deforestation cools climate Yet in the first year after fire, positive annual biogeochemical forcing from greenhouse gas emission, ozone, black carbon deposited on snow and ice, and aerosols exceeds the negative albedo forcing.

20. 2 Changes of forests and their feedbacks Carbon storage Evaporative cooling Albedo decrease If is replaced by grass- land or farmland Feedback Tropical forests StrongStrongmoderate Trend to warmer and drier the air Positive Temperate forest StrongModerateModerateUncertain Positive and negative (Uncertain) Boreal forest ModerateWeakstrong Trend to cool down the surface. Negative

21. Outline 1. Introduction of land-use and land- cover change. 2. Changes of forests and their feedbacks 3. Changes of tropical savanna and their feedbacks 4. Discussion

22. 3 Changes of tropical savanna and their feedbacks

23. Degrades of tropical savanna mainly induced by: Degrades of tropical savanna mainly induced by:  Expansion of agriculture  Increase of grazing  Fire frequency (result from temperature increase)

24. 3 Changes of tropical savanna and their feedbacks Based on model and satellites research:Based on model and satellites research: Degrades of tropical savanna decrease precipitation, increase dry season max temperature, increase dry season maximum wind speed, decrease dry season minimums relative humidity Fire risk increase

25. Outline 1. Introduction of land-use and land- cover change. 2. Changes of forests and their feedbacks 3. Changes of tropical savanna and their feedbacks 4. Discussion

26. 4 Discussion Requirement: Requirement: Meeting immediate human needs and maintaining the capacity of ecosystems to provide goods and services in the future. Meeting immediate human needs and maintaining the capacity of ecosystems to provide goods and services in the future. Mitigate climate change induced by CO2 emission, land-use and land-cover changes. Mitigate climate change induced by CO2 emission, land-use and land-cover changes.

27. 4 Discussion Strategies: Strategies: Effective policy should be promoted to keep the balance between the current requirements of human society and the capacity of ecosystems. Effective policy should be promoted to keep the balance between the current requirements of human society and the capacity of ecosystems.

28. 4 Discussion Strategies: Strategies: Through albedo, evapotranspiration, carbon cycle, and other processes, forests can amplify or dampen climate change. The interactions between all these factors are complex, therefore extrapolation of process- level understanding of ecosystem functioning gained from laboratory experiments or site-specific field studies to large-scale climate models should be enhanced. Through albedo, evapotranspiration, carbon cycle, and other processes, forests can amplify or dampen climate change. The interactions between all these factors are complex, therefore extrapolation of process- level understanding of ecosystem functioning gained from laboratory experiments or site-specific field studies to large-scale climate models should be enhanced.

29. 4 Discussion Strategies: Strategies: In addition, remote sensing data can be employed in many ways to solve environmental problems, such as climate change and carbon cycle, loss of biodiversity, sustainability of agriculture, and provision of safe drinking water. In addition, remote sensing data can be employed in many ways to solve environmental problems, such as climate change and carbon cycle, loss of biodiversity, sustainability of agriculture, and provision of safe drinking water.