Assessment of human impact on Co2 fixation due to vegetation change
Y. Honda, S. Murai
Institute of Industrial Science, University of Tokyo
7-22-1 Roppongi, Minato-Ku, Tokyo 106, Japan
S. Goto
Kanazawa Institute of Technology, Japan
Summary
Abstract
World population has doubled in the past 40 years. It is now 5.3 billion. It is estimated to double again in the next 50 years, reaching 10 billion. The impact on the global environment by human economic activities is stronger than the population increase. The human economic activities produce Co
2 ( green house effect gas). Therefore it is necessary to assess of human impact based on Co
2 fixation change. In this study, the authors estimated Co
2 fixation change due to human activities on the earth.
Inroduction
Assessment of human activities in the geosphere and biosphere is one of the most important problems in environmental sciences. Vegetation changes arise from human activities. For example, in China, large forests have changed to agricultural field for agricultural development. Global change of Co
2 fixation volume result from these vegetation changes. Vegetation change due to human activities is the difference between actual vegetation and potential vegetation. Co
2 is the most important green house effect gas, which is produced from human activities. Therefore, human impacts should be measured based on Co
2 fixation . A world vegetation map has been produced by the authors with the use of NOAA GVI ( global vegetation index ) land use because of human activities. A potential vegetation map has been produced by the authors with the use of weather data and other geographic data. This shows the virgin status of vegetation as generated only from climate and geographic conditions without disturbances due to human activities.
Actual and Potential Vegetation Map
1 Actual Vegetation Map
A global monthly could-free NVI ( normalized vegetation index ) can be obtained from NOAA GVI data. A new vegetation classification ( eight vegetation types ) based on monthly NVI change patterns has been defined by the authors. The author's new definition is shown in Figure 1. For example, tropical forest is defined as an NVI change pattern with a constantly high NVI ( about 0.3) all year . The minimum distance method was applied to the 3 years' ( 1985, 1986 and 1987 ) average NVI and the monthly NVI change patterns shown in Figure 1. The result, a actual vegetation map is shown in Figure 2.
2 Potential vegetation Map
In this study, the potential vegetation has been proposed by the authors as follows. This process is shown in Figure 3. First, as a limit of forest growth, the temperature in the coldest month shall not less than - 5 degree. Second, in the highlands over 3000 m, there is no vegetation. Finally, regarding the arid index, the zoning criteria based on Martonne's AI ( arid index ) are shown in Table 1. Figure 4 shows the potential vegetation map.
AI=P/(T+10)
Where P:
annual rainfall ( mm)
T : he sum of 12 monthly temperatures over 0 degree
divided by 12
