Land use/cover change (LUCC) analysis is a critical component of sustainable land use planning [1
]. In order to better understand the interactions between human and natural phenomena, timely and accurate detection of change in the earth’s surface features is needed [3
]. Furthermore, multi-temporal sets of data are required when monitoring LUCC in order to have effective and accurate evaluations of human impact on the environment [4
]. Remote Sensing (RS) has contributed to the fulfilment of this particular requirement by providing much of the necessary data via satellite imagery. Previous studies have highlighted the importance of LUCC for sustainable land use planning in Southeast Asia [5
]. In the Philippines, biodiversity loss [7
], water quality deterioration [8
], and natural disasters like flash floods and landslides [9
] have been associated with the loss of vegetation cover. However, the century old ‘theory’ that vegetation cover like forests prevent floods by acting as a giant sponge soaking up water during heavy rains, has been refuted by [12
] arguing that there is no scientific evidence linking large scale flooding to deforestation. Nevertheless, it has been stressed that watershed management projects like soil and water conservation and reforestation activities may be beneficial on a local scale, i.e.
, with a well-developed undergrowth and litter layer, forests may contribute to reducing erosion and sedimentation [12
], which have adverse effects on aquatic and reservoir life, potable water quality, irrigation quality and navigation [13
The Philippines has suffered from a substantial loss in natural vegetation, particularly during the last century. From a forest cover of around 90% of the total area of the country in 1521 [14
], this figure has decreased gradually to 62% in 1920, 35% in 1967 and 22% in 1987 through deforestation [15
]. As a counter measure, provisions on environmental law were incorporated into the 1987 Philippine Constitution. Specifically, the Constitution states in its declaration of principles and state policies in Article II, Section 16 that; ‘the State shall protect and advance the right of the people to a balanced and healthful ecology in accord with the rhythm and harmony of nature’. Also, Article XII, Section 2 states that; ‘with the exception of agricultural land, all other natural resources shall not be alienated. The exploration, development and utilization of natural resources shall be under the full control and supervision of the State’. These provisions show awareness of the continuing degradation of the country’s environment, which has become a matter of national concern and why over recent years, reforestation projects have been implemented. Based on the latest statistics produced by the Philippines’ Department of Environment and Natural Resources [16
], the country’s forest cover increased from 18% in 1995 [15
], to 7.168 million ha, or around 24% of the country’s total land area, of which 4.6% is plantation forest. The Philippine Constitution has also been the basis upon which to implement existing forestry and environment-related laws (e.g., the Revised Forestry Code of the Philippines of 1975, and Philippine Environment Code of 1977, amongst others) and to enact new ones (e.g., Executive Order Nos. 23 and 26 of 2011—creating and implementing the National Greening Program, The Philippine Clean Water Act of 2004, The Wildlife Resources Conservation and Protection Act of 2001, and The Philippine Clean Air Act of 1999, amongst others). These policies serve as a legal basis for the barangays, municipalities and cities in their environmental protection and rehabilitation programs.
Some recently published studies relating to LUCC analysis and modelling using medium-resolution satellite images like Landsat images include the following references [17
]. Some of them fall under specific research topics like; urban growth analysis and modelling [17
], LUCC mapping, analysis and modelling [25
], landscape fragmentation analysis [24
], and deforestation driving forces analysis and forest conversions forecasting [19
]. These studies were conducted in various parts of the world. In the LUCC study conducted by [5
] in the countries of South and Southeast Asia, most of the selected representative study areas were watershed-based, whilst some others were administrative boundary-based, including national parks. In the Philippines, Lasco and Pulhin [34
] analysed the forest land use change and its impact on climate change mitigation for the whole country, whilst Estoque and Murayama [17
] monitored the LUCC for Baguio city. In this study, we attempt to extend the monitoring of vegetation cover changes down to the grassroots level, i.e.
, the smallest administrative unit. Land/vegetation cover changes, more often than not, are within the jurisdiction of the local administrative or political unit. It is here where effective environmental protection and conservation project planning and implementation begin. Republic Act No. 7160 [35
], otherwise known as the local government code of the Philippines, states that; ‘as the basic political unit, the barangay
serves as the primary planning and implementing unit of government policies, plans, programs, projects, and activities in the community, and as a forum wherein the collective views of the people may be expressed, crystallized and considered, and where disputes may be amicably settled’. At present, each barangay, which is headed by the barangay Captain/Chairman, has defined powers to enhance its existence as an autonomous part of the municipality or city. The local government code of the Philippines [35
] provides the barangay executive, legislative and adjudicatory powers, and it is in this context that the barangay is important as a unit of analysis for monitoring changes in vegetation covers.
The objective of this study was to assess the vegetation cover for 1989 and 2009 in the barangays of the city of San Fernando, La Union, the Philippines, using medium-resolution RS satellite images and Geographic Information Systems (GIS) techniques for planning vegetation rehabilitation. Having identified the principal changes in vegetation cover between 1989 and 2009 at the barangay level, we discuss the interventions adopted by San Fernando as part of its environmental rehabilitation, protection and conservation agenda.
4. Discussion and Conclusions
This study has used medium-resolution RS satellite images and GIS techniques to examine changes in vegetation cover from 1989 to 2009 in the barangays of the city of San Fernando, La Union, the Philippines, as input in planning vegetation rehabilitation. The vegetation cover change detection and analysis revealed that there were gains and losses of vegetation cover in most of the barangays in San Fernando during the said period. However, despite a decrease in vegetation, especially in ‘dense’ vegetation cover, in some of the urban barangays, there was an overall increase during the 20-year period. This is largely due to the reforestation efforts of both the barangays and the city government of San Fernando. Unfortunately, as there is no report on the survival rates of the planted trees, it is difficult to ascertain the degree of success of the reforestation activities, especially in the rural barangays. Nevertheless, the initiatives taken seem to have paid off, as shown by the results of this study.
The current initiatives of the city government are aimed at ensuring substantial protection and conservation of its entire natural environment amidst the critical challenges of sustainable urbanisation. The management of forested and degraded areas has been one of the current environmental rehabilitation, protection and conservation programs of the city. Other programs include management of the coastal areas and solid wastes, the clean air program, and the water and sanitation program, amongst others [37
]. San Fernando has also enacted ordinances in relation to environmental protection and conservation. The most comprehensive was the City Ordinance No. 2006–013, otherwise known as the Environment Code of the City of San Fernando. In fact, San Fernando has been a recipient of numerous awards related to its initiatives in environmental rehabilitation, protection and conservation. For taking steps to conserve the environment, especially its vegetation cover, the city was the 2nd Runner-up in the Award for the Cleanest and Greenest City in the Philippines in 2003. In 2007, it won the Likas Yaman
Award for Environmental Excellence by the Department of Environment and Natural Resources, Region 1 [37
]. The numerous other awards received by the city in recent years, reflects the success of the city in delivering quality service to its people and in responding to the challenges of urbanisation. The success achieved by San Fernando city may persuade other municipalities in the province, and other cities in the region, to consider undertaking similar projects that would have a positive impact on the environment.
However, the loss of vegetation cover, especially in urban areas, is one problem that the city still has to resolve. In a city like San Fernando, urban forestry and urban greening, which focus on the management of urban green spaces comprising tree stands and individual trees [58
], may be adopted and implemented. The barangays that showed losses of ‘dense’ and ‘open’ vegetation cover due to conversion to ‘non-vegetated land’, as well as those that showed substantial net losses in vegetation cover need to be prioritised in the rehabilitation planning. With the passing of Executive Order No. 26 on 24 February 2011 by the national government, which was created to implement the National Greening Program—to plant 1.5 billion trees in 1.5 million ha by 2016 [59
], it is also expected that more reforestation projects will be undertaken by the barangays and the city government of San Fernando. In principle, the barangay officials, headed by their respective Captains, identify the areas for vegetation rehabilitation. This information is input during the strategic planning by the city government in which the barangay officials are involved. With support from the provincial government, the Department of Environment and Natural Resources (DENR), and other government agencies, including non-government organisations, the city government, who subsidises the rehabilitation programs by providing tree-planting materials, supervision and technical expertise, prioritises those barangays that require immediate attention. In this instance, the RS/GIS-generated information would be useful to the government at both city and barangay levels.
The RS/GIS methodologies used in this case study have demonstrated their usefulness and applicability in the monitoring of barangay-based vegetation cover changes. The classification method using a relatively small number and more general land cover classes, which did not require the pixels to be trained, but allowed the pixels to be classified based on their original spectral values, performed relatively well. The two parameters used in the accuracy assessment of the land cover maps; namely quantity disagreement and allocation disagreement, provide additional important information that the proportions correct and the standard Kappa index of agreement cannot offer. For example, the relative proportions of the two parameters can be used as a basis in determining whether the achieved accuracy levels of the land cover maps strongly support, and/or are appropriate for quantity-based or spatially-based analysis. However, a more specific baseline, particularly on what proportion of quantity or allocation disagreement is acceptable for a particular type of analysis, is yet to be established.
Extending the analysis down to the lowest level of the administrative hierarchy shows an indirect and a modest recognition of the significant role of these units in the rehabilitation, protection and conservation of the environment. The barangays hold very important, first-hand information on how changes in the vegetation cover occur and thus, these barangays, if explicitly involved, may give significant input in the rehabilitation, protection and conservation planning activities. In general, this study has contributed to the understanding of the vegetation cover changes in San Fernando, and will form the basis of the spatial decision-making processes for the environmental rehabilitation, protection and conservation efforts of the city and its barangays. We recommend, however, that the results of this study should be interpreted and used with careful consideration of the accuracy/inaccuracy levels of the classified land cover maps. This is because a part of the land cover change presented could be due to the time difference of the two RS satellite images used. In addition, the different spatial characteristics (e.g., scale/resolution) of the reference data used could also be one source of error affecting the accuracy of the results. Furthermore, it should not be forgotten that the changes in vegetation cover were analysed using land cover maps classified from images captured during the dry season. Land/vegetation cover mapping and change detection using images captured during the wet season should be one of the important concerns for future studies.
Nonetheless, this study has shown the suitability of the application of medium-resolution satellite images in obtaining information about the past and present vegetation cover in the study area. The approach implemented in this study can be used for similar studies in areas where up-to-date information on vegetation cover and cover conversions is as yet unavailable. Such information is extremely valuable for decision making at the lower administrative level, such as the barangay level. However, because in the Philippines most RS/GIS technologies are not yet accessible to the public, and the associated databases are yet to be developed for public use, the city government of San Fernando and its barangays, have to work hand-in-hand with the agencies that are already using these technologies, like the National Mapping and Resource Information Authority (NAMRIA), National Economic and Development Authority (NEDA), and Department of Environment and Natural Resources (DENR). Investment on RS/GIS software, database and technical staff development is needed.