By Chris V. PanganibanInquirer Mindanao Bureau
SAN FRANCISCO, Agusan del Sur — Satellite data showing about140,000 hectares of tree-cover loss in Agusan del Sur from 2001 to 2025 provide an important picture of changing landscapes, but the figures require ground validation to determine whether the loss involved natural forests, plantations, or other tree-covered areas, according to Butuan City-based forestry and mapping specialist Reymar Ballescas.
The Global Forest Watch (GFW) data, which use satellite-based monitoring to track changes in tree cover, show areas where tree canopy has disappeared over time. The recorded loss represents about 18% of Agusan del Sur’s tree-cover area in 2000, highlighting continuing pressure on one of the Philippines’ most important forest landscapes, home to major watersheds, biodiversity areas, and the Agusan Marsh, one of the country’s most significant wetland ecosystems.
However, the figure does not mean that all recorded loss represents permanently destroyed forests.
Data Limits
Ballescas said GFW is a valuable tool for monitoring changes in tree cover, but the system measures the physical disappearance of vegetation and does not automatically identify the type of trees removed.
“Global Forest Watch uses tree-cover loss. As long as there is tree-cover loss, it considers it,” Ballescas said. “It cannot identify if it is natural forest, plantation forest, or other types of trees.”
He said this limitation is important in interpreting Agusan del Sur’s forest-loss figures because the province contains different types of vegetation, including natural forests, commercial plantations, and perennial tree crops.
Areas planted with falcata, mahogany, rubber, durian, marang, lanzones, and other tree crops may appear as tree-cover loss when their canopy is removed, even if the land remains under forestry or agricultural production.
“When it is cut, it is not necessarily deforestation,” Ballescas said. “But if you base it on Global Forest Watch, it is considered tree-cover loss.”
Forest History
Ballescas said understanding Agusan del Sur’s forest changes also requires looking at the province’s logging history.
He noted that the period from 2000 to 2011 coincided with the final years of some Timber License Agreements (TLAs)and the transition from traditional logging concessions toward other land uses, including plantations and agricultural expansion.
He said the significant forest changes recorded during that period require further assessment to determine whether losses were linked to timber extraction, land conversion, plantation development, or other activities.
Validation Needed
Ballescas said GFW data should be examined alongside official land-cover information from the National Mapping and Resource Information Authority (NAMRIA)and field-based GIS validation.
He said separating plantation forests from natural forests is necessary to accurately assess the condition of Agusan del Sur’s remaining forest landscapes.
“Without integrating GIS validation on the ground, real deforestation patterns can remain hidden behind macro statistics,” Ballescas said.
NAMRIA and GFW provide different but complementary information. While GFW monitors annual changes in tree cover from satellite observations, NAMRIA produces official land-cover maps that classify broader vegetation and land-use conditions.
Ballescas said satellite classification also has limitations because some vegetation types cannot be fully identified without checking actual conditions on the ground.
Drivers of Loss
According to GFW data, about 63% of Agusan del Sur’s recorded tree-cover loss occurred in areas where the dominant drivers were associated with deforestation and land-use changes.
Permanent agriculture was identified as the largest driver, accounting for about 86,000 hectares of tree-cover loss. These areas were converted into long-term agricultural production.
Shifting cultivation accounted for about 43,000 hectares, involving temporary farming activities where vegetation is cleared and may later recover. Logging activities were associated with another 7,300 hectares of recorded loss.
The figures show the major pressures affecting the province’s landscapes, but satellite data alone cannot determine whether individual activities were legal or illegal. Such assessments require field investigations, land-use records, and verification by concerned government agencies.
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