Annex 3 - Vulnerability to Damage by International Shipping Activitiesfootnote
Clasification Society 2023 - Version 9.38
Statutory Documents - IMO Publications and Documents - Resolutions - Marine Environment Protection Committee - Resolution MEPC.294(71) - Designation of the Tubbataha Reefs Natural Park as a Particularly Sensitive Sea Area - (adopted on 7 July 2017) - Annex 3 - Vulnerability to Damage by International Shipping Activities1

Annex 3 - Vulnerability to Damage by International Shipping Activitiesfootnote

1 Vessel traffic characteristics

Operational factors

1.1 The vicinity of TRNP is regularly visited by passenger boats carrying scuba divers into the Park and fishing vessels conducting fishing operations outside the Core Zone. Passenger boats voyaging into the TRNP are strictly regulated by the Tubbataha Management Office and must call on the ranger station before proceeding to the designated dive sites (TMO 2008). Such boats are usually smaller kinds of boats and yachts. On the other hand, fishing vessels are often wooden vessels domestically registered, operating from other parts of the country. Management of the TRNP for the most part has effectively kept domestic fishing activity out of the Core Zone, which is designated as a "no-take" area. Fishing operations take place mainly in the Buffer Zone (TPAMB 2014). Both commercial fishers and small-scale Filipino fishers use fish aggregating devices called payao to attract valuable pelagic fish (TPAMB 2014). These types of fish aggregating devices normally involve buoys or floats with clusters of material, floating just beneath the sea surface, and anchored to the seabed with rope or chain. They may pose navigational hazards due to the possibility of entanglement with propellers of passing ships if they are run over. In addition, foreign poachers engaged in illegal fishing have often been found, and boats of local fishers collecting valuable topshells have been seen entering the Park at night (TPAMB 2014). Given the illegality of their activity, poachers surreptitiously entering, operating in, or exiting the Park area may pose collision hazards.

1.2 There has been only one instance to date where the Philippine Government issued a petroleum exploration contract with an area that included parts of the TRNP. This contract has not been implemented as of the time of this application, and the TPAMB has requested the Department of Energy to exclude the area of the TRNP from the said contract (TPAMB 2014).

Vessel types

1.3 Satellite AIS-based data, procured via NORAD and analysed and processed by the Australian Maritime Safety Authority, for the 12-month period from October 2012 to September 2013 show numerous and varied ships passing the TRNP at varied distances. Cargo ships constitute the absolute majority (approx. 70%) of such vessels, followed by tankers (approx. 10%) and other types of ships (approx. 18%). These do not include ships not equipped by AIS, particularly numerous smaller domestic vessels. Available data indicate that at minimum, total vessel traffic passing in proximity of the TRNP Core Zone may be categorized in table 1.

Distance from TRNP Core Zone
Type 20 NM 30 NM 40 NM 50 NM
Cargo 2,225 2,645 2,922 3,152
Fishing 1 1 1 1
Passenger 6 6 10 11
Tanker 288 349 397 442
Other 591 709 778 845
TOTAL 3,111 3,710 4,108 4,451

Table 1: Total number and types of ships that passed within certain distances from the TRNP Core Zone between October 2012 and September 2013

Traffic characteristics

1.4 TRNP lies at the intersection of north-south and east-west shipping routes that traverse the Sulu Sea, connecting the South China Sea to the Celebes Sea and to the Pacific Ocean respectively. At least 4,451 AIS-equipped vessels passed within 50 NM around the TRNP, the majority (some 75%) along the north-south route that connects Northeast Asia with Oceania. Traffic passing along the North-South route is described below likewise in terms of distance from the TRNP Core Zone, set out in table 2, below.

Distance from TRNP Core Zone
Type 20 NM 30 NM 40 NM 50 NM
Cargo 2,100 2,470 2,715 2,882
Fishing 1 1 1 1
Passenger 4 4 7 8
Tanker 198 237 270 291
Other 524 625 689 735
TOTAL 2,827 3,337 3,682 3,917

Table 2: Number and types of ships that passed within certain distances from the TRNP Core Zone, along the North-South routes, between October 2012 and September 2013

1.5 North of the Sulu Sea, ships passing along the North-South route pass into/out of the area through the Mindoro and Tablas Passages astride the Philippine island Province of Mindoro, converging/diverging east of the TRNP (refer to figure 1, below). A significant proportion pass within 10 NM of the Core Zone, i.e. through the TRNP Buffer Zone. This is consistent with actual observations using partial radar coverage from the TRNP ranger station, which has recorded multiple transits of vessels within the Buffer Zone between 2010-2013. These ships then pass out/into the area via the Sibutu Passage.

1.6 International maritime traffic through the Sulu Sea on this route likely connect major ports in the Philippine island of Luzon (e.g. Manila, Batangas) and Northeast Asia with ports in Indonesia, Papua New Guinea and Australia.

1.7 Traffic passing along the East-West route is distributed as follows, likewise in terms of distance from the TRNP Core Zone refer to table 3, below.

Figure 1: Traffic density plot of ships travelling along North-South routes near the TRNP

Distance from TRNP Core Zone
Type 20 NM 30 NM 40 NM 50 NM
Cargo 178 265 350 490
Fishing 0 0 0 0
Passenger 4 4 7 7
Tanker 105 138 167 208
Other 97 130 150 192
TOTAL 384 537 674 897

Table 3: Number and types of ships passing within certain distances from the TRNP Core Zone, along the East-West routes, between October 2012 and September 2013

1.8 Ships passing along the East-West route enter/exit the Sulu Sea through the Balabac Strait; those that traverse through the Bohol Sea are brought in proximity of the southern portion of the TRNP (see figure 2). Compared with ships on the North-South route, less numbers of vessels cross into the Buffer Zone around the TRNP.

1.9 International maritime traffic through the Sulu Sea on this East-West route likely call on major Philippine ports of Cebu and Iloilo from other ports in the Far East. The proportion of vessels that continue on through the archipelago and out by the Surigao Strait from this area is significantly less.

Figure 2: Traffic density plot of ships travelling along the East-West route near the TRNP

Harmful substances carried

1.10 The significant proportion of chemical and oil tankers passing within 10 NM of the TRNP Core Zone is a cause for concern. A closer examination of the AIS data show that shipping routes running through the east and west of the Park bring vessels in closest proximity to the TRNP Core Zone. Data indicates that the major route is to the east, with more than 774 vessels passing along a north-south route within 7.5 NM of the Park. This included 89 chemical tankers (11.49%) and 185 oil tankers (23.9%). Several thousand vessels pass annually along this north-south route further offshore. To the west of the Park, some 165 vessels including 31 chemical tankers (18.7%) and 46 oil tankers (27.9%) travelled within 9 NM of the Park along another north-south route.

1.11 The threat of oil and chemical pollution and potential catastrophic impact on coral reefs is well known. With oil and chemical tankers passing so close to the TRNP, there is a significant risk of accidental spills and even grounding on the reefs. Notably, the two successive ship-grounding incidents that took place in 2013 (the USS Guardian in January and the Min Ying Pu in March) were both travelling along north-south routes.

2 Natural factors


2.1 The TRNP is located in a region of the Sulu Sea of varied depth ranging from 1,490 to 2,769 m. Charts indicate that the Tubbataha Reefs rise above these deep waters abruptly, forming separate underwater pinnacles topped off by coral reef structures. Depths can change radically, from 1,000 m to less than one metre within a distance of only one nautical mile around the reefs. This steeply rising slope contributes significantly to the risk of grounding for vessels in the area. The reefs provide little protection from strong winds and surface currents.

2.2 Hydrographic information from the Philippine Coast Pilot Guide (NAMRIA 1995) describes all reefs within the TRNP in very clear terms as inherent dangers to navigation:

  • "The North and South Atoll of Tubbataha Reefs are considered to be dangerous reefs separated by a deep channel about 5 miles wide.

  • The North Atoll is oblong in shape and encloses a lagoon 2 miles wide and 5 miles long, with depths of 7.3 to 32.9 m at mud bottom. There are no passages through the barrier reef into the lagoon; only small launches can cross the barrier reef at high tide. Deep water is close to the outer edge of the reefs, and no anchorages are available. North Islet, Central Islet, and a number of small black rocks are the only objects that appear above high water. At low water, a large number of detached sand cays or ridges, each about 91 m long and 9 to 18 m, can be seen along the entire length of the reef. North Islet is covered with gravel and some guano.

  • The South Atoll is about 4.5 miles long North and South with several black rocks and sand cays visible at high water.

  • South Islet is made up of loose, white sand about 1.5 m above high water, and is protected by riprap. The 39.6 m cylindrical, steel-framed tower which used to be a lighthouse on this islet is very prominent.

  • Jessie Beazley Reef, about 18 miles north of Tubbataha Reef Light, extends about 640 m in a north-westerly direction and is about 137 m wide. At the centre of the reef is a small hill of broken coral about 1.8 m high, devoid of vegetation. At low water, the reef bares over a considerable area. Birds can sometimes land on the bare parts of this reef. White sand cay is readily visible by day at a distance of 3 to 5 miles."


2.3 The Sulu Sea within which the TRNP is situated is a deep sea in the Southeast Asian region located along the south western quadrant of the Philippines. It is bounded by Palawan Island on the west, Mindoro Island to the north, Panay Island and Mindanao Island to the east, the Sulu Archipelago to the southeast, and Borneo to the southwest. Weather and climate is strongly influenced by the East Asian Monsoons and the seasonal migrations of the Inter-tropical Convergence Zone (ITCZ) and the El Nino Southern Oscillation (ENSO). A north-easterly wind prevails in winter and a south-westerly wind prevails in summer, but otherwise it is very variable during the transitional periods (Oppo et al. 2003; Latiff et al. 2014). Sudden heavy rainfalls are known to occur appear within the Sulu Sea region, posing hazards to shipping (Butt and Johnson, 2013).

2.4 Rough seas are present from July to October and November to March. Rainfall is highest in the Sulu Sea from May through November. From June through September, the ITCZ rainfall merges with the East Asian Monsoon. By October and November, the East Asian summer monsoon rains are over, and the dry season starts in the northern SCS but reaches its seasonal maximum in the southern SCS due to the southward position of the ITCZ (Oppo et al. 2003). The Philippines, including the Sulu Sea, is also located within the tropical "typhoon belt" regularly traversed by typhoons. On average, about 20 tropical cyclones develop within the Philippine Area of Responsibility each year, of which around half make landfall (PAGASA 2009). These disturbances periodically aggravate weather and sea conditions in the Sulu Sea, thus sudden violent storms, heavy rainfall, and strong winds increase the risk of navigational incidents.


2.5 The Sulu Sea is a semi-enclosed basin connected to surrounding seas over shallow sills. It is surrounded by major landmasses such as Palawan, Borneo, Mindanao, Panay, Antique, and Mindoro, as well as connecting several bodies of Philippine waters such as the Linapacan and Balabac Straits, the Sibuti Passage, Moro Gulf, Dipolog Strait, Bohol Sea, Panay Gulf, and Mindoro Passage. The Mindoro Passage to the north/northwest is the deepest passage at 420 m, connecting the Sulu Sea to the South China Sea, and with the Java Sea across the shallow Sunda Shelf. The Sibutu Passage to the south is the next deepest passage, connecting the Sulu Sea to the Sulawesi Sea (Oppo et al. 2003). The TRNP lies between these two passages, which also form the entry/exit points for North-South routes traversing the Sulu Sea. Water circulation patterns in the Sulu Sea show that there is an inflow from the South China Sea at the Mindoro and Balabac Straits, and an outflow into the Sulawesi Sea at the Sibutu Passage. There is a cyclonic circulation in the southern basin (Han et al. 2009). A strong current forms in the northeast Sulu Sea where currents from the Mindoro and Tablas straits converge. These converging currents are also entry/exit points for North-South shipping routes. Surface current speeds have been measured to be as much as 100 cm/sec (Han et al. 2009).

2.6 Strong westward currents in the Bohol Sea carry the surface water of the western Pacific from the Surigao Strait into the Sulu Sea via the Dipolog straits. In the Sibuyan Sea, currents flow west which carry the surface water from the Western Pacific near the San Bernardino Strait into the Sulu Sea via the Tablas Strait (Han et al., 2009). Surface currents exhibit strong variations or reversals from winter to summer, with the TRNP forming a centre around which the currents circulate. Generally, during the South West Monsoon, waters flow in a clockwise motion around the TRNP, driven by currents from the Dipolog and Linapacan Straits (Han et al., 2009). The fact that TRNP is located at the centre of this circulation pattern increases the possibility that any discharges or vessels adrift near TRNP will likewise be carried around and into its boundaries.

3 Other Information

3.1 Since 2010, TRNP Park Rangers have been collecting and compiling information on impacts of international shipping traffic around the TRNP, albeit with limited capabilities due to the isolation and inherent limitations of surveillance capabilities of the Park Ranger Station. Annual records have been based on personal observations of Park Rangers and extremely limited radar coverage of the immediate vicinity of the TRNP. A review of the records of limited radar coverage during the period from 2010-2013 echoes the upward trend of ship transit, notably passing through the TRNP Buffer Zone. Refer table 4, below.

Year No. of Ships Tracked Monthly Average Rate of Increase
2010 3,358 280 -
2011 4,253 363 23%
2012 3,616 302 -20%
2013 5,546 462 35%

Table 4: Number of ships tracked by the TRNP Park Ranger Station with extremely limited radar coverage

3.2 The upward trend in ship transits around the TRNP translates into an expected increasing risk in shipping-related impacts, both operational and accidental. Ship groundings have been demonstrated as the most prominent risk, followed by pollution from discharges. A recent study of maritime trade and traffic trends in the Sulu-Sulawesi Region concluded that all global trade forecasts indicate "higher volumes of international shipping will transit through or close to Philippine national waters and as a consequence increase the vulnerability of the Tubbataha Reefs Natural Park". It pointed out that the potential increase in very large vessels transiting through the area to service the ore, coal and LNG trades, and growing populations around the Sulu-Sulawesi Region that would likely also increase import activities and the corresponding number of vessels operating in the area, also posed significant threats. (Butt and Johnson 2013).

3.3 A separate study that mathematically modelled ship incident risks around TRNP corroborated the above report by concluding that "incident probabilities and monetary value at risk (MVR) have increased in recent years; the probability of pollution in 1999-2007 increased by about 60% for South-East Asia compared to 1979-1998, and the associated MVR for tankers has doubled." It further noted that the increase of pollution risk close to the TRNP is even larger (Heij et al. 2013).

3.4 Park rangers have documented a notable increase in the amount of foreign, non-Philippine marine debris (product packaging, plastic containers) collected at the TRNP ranger station, indicating a clear correlation between the amount of shipping traffic and the amount of marine debris washed ashore at the park ranger station (refer to table 5, below).

Year Kg of debris collected
2010 198
2011 627
2012 635
2013 1,460

Table 5: Weight of marine debris collected annually by TRNP Park Rangers

3.5 Ship groundings have occurred on Tubbataha Reefs. Available records indicate that as early as 1925, the British steamship Egremont Castle ran aground near the lighthouse on South Atoll, and in June 1949, the US steamer Flying Cloud ran aground near the South Island. Despite modern navigational technologies and accurate charting, such groundings have continued to take place. In January 2013, the US Navy minesweeper USS Guardian ran aground on the South Atoll and had to be completely dismantled for removal. Shortly after, in March 2013 the Chinese fishing vessel Min Ying Pu ran aground on the North Atoll and had to be salvaged (TPAMB 2014). These successive incidents in the TRNP have demonstrated its continued exposure to high risks posed by international shipping activity. The increase in shipping activity around the TRNP denotes a corresponding increase in risks of similar ship groundings.

3.6 Chemical and oil spill simulations conducted for the Tubbataha Management Office by the Physical Oceanography Laboratory of the Marine Science Institute show that at any given month, due to the proximity of several shipping routes around the TRNP, there is a very high probability that pollutants from chemical or oil spills will cross into the boundaries of the TRNP. Depending on the distance, time of year, monsoon and sea conditions, in the worst case scenario (outside of a vessel grounding) pollutants can take as little as four hours for chemical spills and five hours for oil spills. In the best case scenario, a chemical/oil spill threat can take as much as 8 days before reaching the TRNP. Again, the increasing trend in shipping activities around the TRNP will result in a corresponding increase in risks of accidental chemical and oil spills (Villanoy et al. 2015).

3.7 In case of a marine incident at or in the vicinity of the TRNP, there are only two government vessels available in the nearest Coast Guard District operating base at Puerto Princesa City, a 35 m Search and Rescue Vessel and a 30 m Fisheries Monitoring, Control, and Surveillance patrol vessel. It will take such vessels approximately 10 hours to respond to an incident at the TRNP, assuming that the said vessels are not being used elsewhere and are capable of taking the stricken vessel in tow. Private salvage companies based in Manila with dedicated salvage capability will take at least 24 hours to respond to a marine casualty or incident in the vicinity of the TRNP. Moving the concentration of shipping away from the Park significantly reduces the risks of incidents and may provide just enough additional time for Park Rangers and other government agencies to prepare adequate incident response measures.

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