Land use change

Another model, first introduced by Moore, et al. (2i), was used to examine the role of terrestrial vegetation and the global carbon cycle, but did not include an ocean component. This model depended on estimates of carbon pool size and rates of CO2 uptake and release. This model has been used to project the effect of forest clearing and land-use change on the global carbon cycle (22, 23, 24). 

Several studies, based on models, examined the effects of land-use change on the global carbon cycle and conclude that there is a net release of carbon due to land clearing. However, the results and conclusions of these studies are based on assumed sizes of vegetation carbon pools which are inputs to the models. For example, Melillo et al. 24) concluded that boreal and temperate deciduous forests of the northern hemisphere are net sources of atmospheric carbon. Their analysis used values for carbon density derived by Whittaker and Likens 19) from work by Rodin and Bazilevich (27). Rodin and Bazilevich extrapolated results of small, unrelated studies in Europe and the USSR to estimate total biomass of Eurasian boreal and temperate deciduous forests. Their estimates have since been extrapolated to forests worldwide and are used often today. 

Land use changes in the tropics have resulted in a landscape characterized as a mosaic of logged forests, cleared fields, and successional forests. This results in the transformation from extremely fire resistant rainforest ecosystems to anthropogenic landscapes in which fire is a common event (16, 17), Fires occur in disturbed tropical forests because deforestation has a dramatic effect on microclimate. Deforestation results in lower relative humidities, increased wind speeds, and increased air temperatures. In addition, deforestation results in increased quantities of biomass that are susceptible to fire. This biomass may be in the form of forest slash, leaf litter, grasses, lianas or herbaceous species (16, 18). 

The terrestrial biota seem unable to take up much of the excess CO2. In fact, a careful assessment of the impact of deforestation and land-use changes indicate that the terrestrial biota has been a considerable source of CO2 during the past century (Bolin, 1977 Woodwell et al, 1983). A complex effort to deduce mankind s impact on terrestrial biota using a bookkeeping model based on historical records on land use in all parts of the world (Moore et al, 1981 Houghton et al, 1983 Woodwell et al., 1983) gives the curves in Fig. 11-25. Woodwell et al. (1983)... 

Houghton, R. A. (1993). Emissions of carbon from land-use change, paper presented at the 1993 Global Change Institute on the Carbon Cycle, Off. Interdisciplinary Earth Stud. Univ. Corp. Atmos. Res., Snowmass, Colorado, July 18-30. 

Foodwebs of the Delta have been altered in many ways through the multiple changes that have occurred within the Delta in recent decades. For example, the turbidity and organic matter supply to the Delta have been generally decreasing due to land use changes and upstream reservoirs. Phytoplankton populations also have... 

Eighteen percent of Greenhouse Gases (GHGs) stem from land use change , a euphemism for deforestation. A cmcial challenge is how to avoid the problem... 

Metzger M, Rounsevell M, Acosta-Michlik L, Leemans R, Schroter. The vulnerability of ecosystem services to land use change. Agriculture, Ecosystems andEnvironment, 2006.114 pp. 69-85. doi 10.1016/j.agee.2005.11.025... 

Figure 5. Carbon footprint of different types of food products at retail. Average values estimated to be representative for food products sold on the Swedish market. Error bars show ranges of values found in the literature. Emissions from land use change and carbon stock changes in soils are not included [47]...

The distribution of SOC with depth is attributed mainly to continuous input and decomposition of soil organic matter (SOM), and correlates directly with soil development and SOM turnover (Chen et al. 2005). Regional, continental or global models are useful to understand SOM dynamics according to land use changes and management practices (Cole et al. 

Scott NA, Tate KR, Ford-Robertson J, Giltrap DJ, Smith CT (1999) Soil carbon storage in plantation forests and pastures land-use change implications. Tellus B 51 326-335... 

Land spreading, solid waste volume reduction via, 25 870, 874 Land transport, of food, 21 566 Land treatment, defined, 3 759t Land use changes, effect on stream water, 26 27-28... 

---