The Micro-analysis of Land Use/Land Cover Change
The raw and classified imageries of the watershed were carefully compared and areas with very evident change were separated and analyzed individually. Four sub-areas were selected and four major factors of change were identified.
Figure 3 shows imageries taken before and after the 1990 earthquake. The earthquake caused landslides on very steep, unstable or disturbed slopes. The area with the cyan color on Figure 3 #2 used to be the dwelling of a small group of settlers. This area was very steep. When the earthquake occurred, the whole side of the mountain where their houses were built slided and all the 30 people died except for one. An after effect of the earthquake was the widening of the rivers and tributaries due to siltation. Landslides were very common on the western side of the watershed, but very few on the eastern side.
Rice cropping was performed in the rice paddies three times a year and farmers do not plant at the same time. Figure 4 shows imageries of paddy fields while with rice (Figure 4 #1 and #3) and while on fallow (Figure 4 #2 and #4). This type of land use/land cover change occurred actively only on the floodplains and valleys of the watershed but very minimal on the highlands where rice croppings were done on terraces.
The climate inside the watershed was characterized in to two general categories: wet and dry. Not only did the availability of rainfall had an effect on agriculture but also on the grasslands and brushlands of the watershed. Figure 5 shows imageries of grasslands and brushlands. During the dry seasons, drying up of grasses and grass/brush fires were very common. This was further enhanced by the occurrence of the El Nino. Figure 5 #2 showed a high reflectance on the grass areas because the grass cover was thin and dry.
The log ban, together with the forestry development programs had resulted to the growth and development of forests lands. Figure 6 showed that there was an improvement in the land use/land cover from 1988 to 1998. The improvement in the land cover for this site was due to the governments promotion of agro-forestry.
Figure 3. The effect of natural disasters on land use/land cover
(#1) raw 1988 (before the earthquake),
(#2) raw 1992 (after the earthquake),
(#3) classified 1988 (before the earthquake) and
(#4) classified 1992 (after the earthquake).
Figure 4. The effect of human intervention (agriculture) on land use/land cover
(#1) raw 1988 (planted),
(#2) raw 1996 (fallow),
(#3) classified 1988 (planted) and
(#4) classified 1996 (fallow).
Figure 5. The effect of climate on land use/land cover
(#1) raw 1997 (wet),
(#2) raw 1998 (dry),
(#3) classified 1997 (wet) and
(#4) classified 1998 (dry)
Figure 6. The effect of improvement on land use/land cover
(#1) raw (1988),
(#2) raw (1998),
(#3) classified (1988) and
(#4) classified (1998)
Conclusion
I therefore conclude that there were three major factors which affected land use/land cover of Upper Magat Watershed. They were climatic conditions, human activities through agriculture, deforestation and reforestation, natural disasters like landslides from earthquakes and soil erosion.
Further Studies
Now that the major factors which caused change in the land use/land cover of Upper Magat Watershed has been identified, they should be considered in the land use/land cover change analysis. Spatial dimension should also be established for these factors because their activities were site specific and not applicable for the whole watershed.
References
- Climatological and Agrometeorology Branch, Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), Department of Science and Technology (DOST), August 1992. Climate of the Philippines Brochure, Quezon City, Philippines.
- Climatological and Agrometeorology Branch, Philippine Atmospheric, Geophysical andAstronomical Services Administration (PAGASA), Department of Science and Technology (DOST), 1997. Primer on El Nino/Southern Oscillation (ENSO), Quezon City, Philippines.
- Department of Environment and Natural Resources Web Site, http://www.denr.gov.ph
- Land Use Land Cover Change (LUCC) Team, Philippine Land Use and Land Cover Change Case Study, Makati City, Philippines.
- Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), Rainfall and Tropical Cyclone Climatological Norms of the Philippines (1961-1990), Quezon City, Philippines.
