AMWS, an EMBC Protected Area, Celebrates World Wetlands Day
A Sponge of the Earth, or Nature’s Kidney, in the Southern Philippines’ hemisphere. The Lungs of Mindanao Island.
A Wetland of Global Significance and regional corridor conservation.
These are just some of the colorful analogies that describe the Agusan Marsh Wildlife Sanctuary (AMWS).
A declared Philippine Protected Area, AMWS is one of the most significant wetlands in the country, having been listed since November 1999 as a Wetland of International Importance under the Ramsar Convention (site no. 1009).
By November of 2018, the ASEAN Heritage Parks declared AMWS as its 9th ASEAN Heritage Park in the Philippines and the 42nd in the overall ASEAN Region.
However, AMWS faces threats that endanger its important ecological functions and services, including pollution from upstream effluents, wildlife and timber poaching, and the pressures of unregulated land use and increasing population.
Being one of the sites within its Eastern Mindanao Biodiversity Corridor, the BD Corridor Project will address the root causes, barriers and threats that this unique ecosystem is currently facing.
As part of its mandate, the Project will be addressing policies, regulations and approaches that breed such barriers and threats, and fragmented implementation of key programs to effectively address such threats to BD corridor connectivity.
WLI+PAMO Data
Seven (7) habitat types of AMWS:
a. Open water (oxbow lakes, floodplain lakes and ponds) – Based on the turbidity of water, two subtypes are present in the marsh, namely clear water habitat and turbid water habitat. The turbid open water is filled with silt materials. The presence of macrophytes intensifies faunal biomass and species diversity in clear water habitats, supporting large populations of invertebrates, fishes and fish-eating birds. Low biodiversity are present in turbid open water habitats because it inhibits natural productivity of phytoplankton and macrophytes. Clear open water are acidic and colored by humic acid because of a high rate of decomposition of organic matter. This type of habitat is fairly rare in the Philippines.
b. Flowing water – There are two subtypes of flowing water present. These subtypes are based on differences in flow characteristics, depth and biological characteristics. The first subtype is unidirectional flow. This means flowing in one direction such as the Agusan River, some other major tributaries like the Simulao, Adgaon and Umayan Rivers and some other minor tributaries. The second sub type has bidirectional flow such as rivers and creeks which flow into lakes when the Agusan River rises, then flow back out of the lakes when the water level recedes. Agusan River rises in July and August and then flow out of the lakes into the river in the March-May period. Main concern in this habitat type is the high sediment load in them, which had been aggravated by deforestation, and other activities in the catchment. High silt load has been reducing diversity as they interfere with the respiration of fishes and other organism.
c. Herbaceous swamp – Open and very extensive in the marsh, this habitat type is composed mainly of sedges, grasses and ferns. Their occurrence is related to the period and depth of inundation and stage of succession in the area. This habitat is almost undisturbed because they are difficult to penetrate.
d. Scrub swamp – This is quite similar to herbaceous swampland areas. The difference is that is has stunted trees of Barringtonia and Nauclea. Certain birds use this habitat for cover and roosting.
e. Swamp forest – Their subtypes were identified based on species composition. These are: (a) terminalia forest; (b) peat swamp forest; (c) sago swamp forest; and (d) mixed swamp forest.
There are several areas in the marshland that has pure stands of Terminalia copelandii species. The said species is similar to Terminalia catappa that is locally known as “talisay”. This habitat observed to be slowly diminishing in terms of number and area occupied is the “kalanipawan” (Terminalia forest) habitat. It is a type of swamp forest dominated by Lanipao (Terminalia copelandii) and found mostly on periodically inundated areas. In AMWS, the forest type can still be found intact in Rosario and Loreto. In La Paz,Talacogon and Bunawan, fewer trees are present and exist individually due to extensive land conversion and cutting of trees in the past. The species was used by Manobo to build boats and as floaters for their houses during flooding season.
This area is largely composed of Barringtonia and Nauclea. This habitat type is very rare in the Philippines. If ever they exist elsewhere, they are only isolated remnants consisting of a few hectares. Thus, Agusan Marsh is considered as the largest and the last stronghold in the Philippines for this unique habitat.
Tiga (Tristaniopsis micrantha Merr.) is a Philippine endemic species commonly found in the mixed swamp forest in Talacogon. The habitat which the species dominates is called “Katigahan” by Manobo. Based on the survey, about 153 individuals were recorded belonging to 15 species (species richness). The five most dominant species of the habitat include Aemajan (19%), Tiga (18%), Likayan (16%), Sainganan (14%) and Yaku-yako (12%). Most of the species in the Katigahan were utilized as lumber or post for house construction and related uses that requires naturally durable type of woods. Associated species include Libas (Spondias pinnata), Kandiis (Garcinia parviflora), Bitaog or Palomaria (Calophyllum inophyllum) and Kabak (Nauclea orientalis). The habitat has an evenness index of 0.619, which means that species are more equal or numerically even in the community compared with other. The area has a mean density of 1,217 individuals per hectare, considered to be denser compared with the other mixed swamp forest in the marsh.
This forest type is the rarest swamp forest type in the marsh and holds the only largest Sago Palm forest in the Philippines. This forest dominated by Metroxylon sagu is rare in the Marsh. It is used by the natives as construction material for their floating houses. It is located in North-West portion and shared by the municipalities of La Paz, Talacogon and Rosario, all in the province of Agusan del Sur.
According to local residents, the kalumbiyahan covers an estimated area of 3,000 hectares and continuously expanding because of their conservation practices. A candid transect on dry season passing the innermost portion of the forest would take a day and a half to reach its other side. However, the area is very much accessible by boat during flood. The Manobo believed in the existence of supernatural beings in the forest. Before going inside for harvest, it is strongly recommended to offer a small ritual. They believe that by not doing so, the forest will become a labyrinth were bad spirits make fun of you making it very hard to find your way. Lumbia is the source of sago starch that is known to be the raw material for sago food product such as puddings, noodles, breads, and also serve as a thickener. Aside from being used as food during times of hunger, the lumbiya forest also served as a habitat for various fauna species. During data gathering, several footprints of wild boars were observable in the area. Large snakes such as banakon and sawa also thrives in the innermost portions of the forest. The lumbiya habitat has a richness of 5 species which was dominated by Lumbiya (Metroxylon sago) comprising 86% of the community. Associated tree and tree-like species include Uyango (Pandanus basicularis), Banaba (Lagerstroemia speciosa), Sainganan, and Badawa.
The peat swamp forest type in the marsh is the next rarest swamp in the Philippines. It covers the largest remaining intact peatswamp forest in the country, the Caimpugan peatland which I estimated to store a total of 22.8 million tons of Carbon within its 5,487 hectares area.
f. River bank – This habitat type is composed of slightly different vegetation type than the lower areas. They suffer the least inundation due to raised banks along the rivers and creeks. Currently, they only exist along the more isolated creeks because they have been cleared along major rivers which had served as major transport corridors.
g. Inundated forest – This habitat type is thought to be relatively rare in the Philippines. In Agusan Marsh, it can no longer be identified on the ground but they may still be found along the western periphery of the marsh where there has been less disturbance. This habitat maybe inundated but the soil is not permanently water-logged.
The AMWS hosts a total of more or less 1,100 species of unique assemblage of flora and fauna with 314 endemic species recorded. This include the following:
- 721 plant species including 3 species of bamboo.
- 216 species of birds (67 Phil. Endemics, 48 Mindanao endemics)
- 31 species of mammals (15 Phil. Endemics, 1 Mindanao endemics)
- 53 species of reptiles
- 33 species of amphibians (17 Phil. Endemics, 10 Mindanao endemics)
- 65 species of butterflies (3 are rare: Papilio antonio, Graphium cordus and Graphium idaeoides)
- 11 species of crustaceans
- 50 species of fish
- 9 species of mollusks