Integration of RS and GIS to Assess Human Impact on Ecosystem Change in Llanos Area (Venezuela)
3. Research Methodology
The framework for remote sensing application in landscape ecology must be considered in reference to both the spatial and temporal condition. The individual research question associated with space, time and dynamics. (Quattrochi, D.A., and Pelletier, R.E., 1990) An appropriate data collection design can be employed within the scope of an investigation to provide answers to the specific landscape questions under consideration. For to assess the human impact on the ecosystem change these questions are not all-encompassing and should be addressed. The landscape processes associated with the landscape spatial and temporal dynamics should be observed and measured.
Figure 1 Methods of implemented integrated GIS and RS assess to human impact in the Llanos area
To take into account the landscape ecological characteristics in the study area and the research question and the limitation of available data, the framework of implemented methods in this research is:
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Constructing the spatial ancillary database including road map and residential area map etc.
- Interpreting the ecosystem map from Landsat TM.
- Employing the change detection technique to derive the ecosystem temporal change 1960 to 1988.
- Extracting the main human impact factor ¾ dikes by using knowledge based and fuzzy classification.
- Carrying out the landscape fragmentation analysis in different scales ¾ to calculate the landscape pattern index that correlated with the degree of human manipulation of landscape in GIS environment to compare the spatial difference of landscape change in modular area and non-modular area.
- Applying GIS to model the human impact on ecosystem change to take into account the anthropogenic factors such as distance to dikes etc.
Figure 1 gives an overview about implemented methods of integrated GIS and remote sensing to assess human impact in the study area.
4. Results
Temporal changes in a landscape could include change in (1) patch number, (2) patch size, (3) number and type of corridors, (4) number and type of dispersal barriers, (5) probability and spread of disturbance. (Turner, 1988) The emphases in this study are 1,2,4 and 5.
The change detection is a technique that detects the changes between two data sets, the Ecosystem map 1960 and the Ecosystem map 1988 pixel by pixel. The implementing of the post-classification is a program in GIS environment (ARC/INFO). Based on the results of landscape change detection, the Ecosystem change map, the area of ecosystem temporal change can be identified.
The patch number and the total boundary length in 1988 increase enormously comparing with in 1960, the average patch size is shrinking. The construction of dikes is the dissection, dissect or subdivide of the landscapes into sections. Fragmentation predominates in the present phases of landscape change.
Analysis of the landscape type change, the River forest and the Hyper-seasonal savanna, which dominated the study area and relative stable comparing with the other types. However, it is remarkable that the area of Hyper-seasonal savanna inundated by water is more than the Semi-seasonal savanna, and the Semi-seasonal savanna is the lower part in the study area. The trend of the landscape change indicates the landscape transformation that is not a natural process.
Using GIS the overlay analysis function, the ecosystem map 1960 was intersected with the dike map. The patches that were dissected by dikes were reselected. The areas of each landscape type were counted as disturbed by the construction of dikes. For the landscape types within the study area, the frequencies of disturbance are more than 80%.
