Treasure our Rajang mangroves

Each year World Wetlands Days is celebrated on 2 February to mark the adoption of the Convention on Wetlands of International Importance (Ramsar Convention) in the Iranian city of Ramsar in 1971.

This year’s celebration is themed ‘Wetlands for Disaster Risk Reduction’. This celebration focuses on the need for healthy wetlands which help us cope with extreme weather events, act as natural safeguard against disasters, and sustain lives. Wetlands are areas where water is the primary factor that controls the environment and its associated plant and animal life.

Natural wetlands comprises freshwater swamps, peat swamps, river systems, floodplains, natural lakes, marshes, mangroves, sandy beaches, rocky shores, nipa swamps, coral reefs, seagrass beds and mudflats. Manmade wetlands comprise rice fields, mining pools, ponds, reservoirs, sewage farms, constructed lakes and marshlands.

In this article, WWF-Malaysia highlights the importance of conserving the mangroves along the Rajang delta and their importance for the survival of a vulnerable species, Irrawaddy dolphins.

Irrawaddy dolphins are categorised as vulnerable in the IUCN Red List of Threatened Species. Photo credit: © Sarawak Dolphin Project

Irrawaddy dolphins are categorised as vulnerable in the IUCN Red List of Threatened Species. Photo credit: © Sarawak Dolphin Project

KUCHING: The mighty Rajang River, the longest in Malaysia, supports a significant wetlands area in the country that provides priceless socio-economic value to the people and environment.

The Rajang River provides its surrounding human population with resources such as food and water, to services such as transportation, power generation, recreational activities, and opportunities for income generation through tourism. The river is also an important area for research and educational activities, and is home to the Irrawaddy dolphin Orcaella brevirostris.

The Rajang delta is a busy waterway that includes deep anchorage port operations and various other industries. Rapid developments near the delta over the years have raised concerns on the long term conservation of its resident dolphins, and the need to protect them from being threatened by human activities.

Surprisingly, Irrawaddy dolphins still strive at the delta, particularly near the Rajang mangroves which provides them protection and food.

The mangrove root systems of the Rhizophora and Avicennia protect the riverbanks from erosion. In these parts of the mangroves system, the water is calmer and clearer, making it an ideal habitat for Irrawaddy dolphins.

A dolphin waiting for its share of fish caught by a fisherman. Photo credit: © WWF-Malaysia/Mohd Khairulazman Sulaiman

A dolphin waiting for its share of fish caught by a fisherman. Photo credit: © WWF-Malaysia/Mohd Khairulazman Sulaiman

In a study conducted in 2009 to 2010, entitled Distributions, Densities and Abundance of Irrawaddy Dolphins (Orcacella brevirostris) in Batang Rajang and Batang Saribas of Sarawak, Malaysian Borneo, jointly by Sarawak Forestry Corporation (SFC), Institut Penyelidikan Marin Borneo of Universiti Malaysia Sabah and Institute of National Oceanography and Environmental of Universiti Malaysia Terengganu, it was reported that there is high probability of sighting, density and abundance of this mammal at the lower river segments.

The study, which included a 118.8km long survey from the Rajang delta (the estuary where Rajang Mangrove National Park is located) upstream to Sibu town, observed that the distribution of the dolphins is determined by the combination of pH, conductivity, turbidity, dissolved oxygen and surface temperature of the water. High conservation value areas (HCVA) as well as tourism hot spots were also identified. The study also noted the use of the river for logging and timber-related industries, transportation and berthing place for large deep sea vessels at Tanjung Manis.

The study was presented at the International Conference of Marine Science and Aquaculture 2014 in Sabah by one of the authors, James Bali from SFC.

The area between Surat River and Loba Palai of the Rajang River has been identified as HCVA for Irrawaddy dolphins. This area accounted for 64.20% of the total sightings during the study, which represented an average of one sighting for every half hour period.

The study made recommendations for periodic monitoring to observe population trend and habitat utilisation of the Rajang Mangrove National Park. It also asked for the development of eco-tourism activities such as dolphin watching and for public awareness campaigns to be organised.

It pointed out that more research is needed to fill the knowledge gaps particularly on the association of Irrawaddy dolphin occurrence with food sources availability, distance from river mouth, tidal stages and water depth. Other research identified include the need to study home range – which may be carried out using satellite tracking, photo identification or DNA studies; and population estimation through periodic monitoring programmes.

When Batang Rajang is calm along the mangrove forests, it provides a safe haven for Irrawaddy dolphins. Photo credit: © WWF-Malaysia/Mohd Khairulazman Sulaiman.

When Batang Rajang is calm along the mangrove forests, it provides a safe haven for Irrawaddy dolphins. Photo credit: © WWF-Malaysia/Mohd Khairulazman Sulaiman.

In a rapid survey conducted by WWF-Malaysia in 2015, it is noted that the dolphins co-exist well with humans, but this also expose them to human-animal conflicts. The communities here are predominantly fishermen. Sometimes, these mammals are accidently caught and suffered the fate of being drowned when they get entangled in fishing nets.

Besides that, human activities upstream will also have detrimental impacts upon dolphins.

Floating plastic bags, indiscriminately thrown into the river or sea, are also dangerous to the dolphins as they might mistake them as food. Pollution and contaminant run-off from land can also affect the food chain and result in the depletion of food source such as fishes, crustacean and cephalopods which the dolphins feed on. Permanent physical barriers such as weirs and dams impede dolphin movements upriver, but they may also cause changes to downstream flow.

Developmental activities, largely being carried out in the coastal region and the delta area, may have impacts upon long term survival of dolphins, causing them to become even more threatened.

We should not shrug off these threats that may one day wipe off the population of Irrawaddy dolphins from our waters. For instance, this species has been regarded as ‘functionally extinct’ in Laos. Our dolphins could receive the same fate like the ones in Laos if no holistic conservation action is taken.

From the results of the WWF-Malaysia’s rapid survey, the Rajang delta is regarded as one of the key habitats for wildlife, including dolphins, and deserves long term conservation attention. The area provides invaluable ecosystem services for human and wildlife. The delta is also home to protected species under the Sarawak Wild Life Protection Ordinance 1998 such as proboscis monkeys, silvered langurs, lesser adjutant storks, raptors, hornbills and migratory birds.

The proboscis monkey is an endemic species to Borneo and can be found in Rajang delta. Photo credit: © Jason Hon

The proboscis monkey is an endemic species to Borneo and can be found in Rajang delta. Photo credit: © Jason Hon

Such a high concentration of wildlife species indicate that the delta is an important habitat that warrant proper management and conservation attention. If developed properly, the variety of species here can be the stars of ecotourism activities at the delta. The local communities can provide boat services and serve as local guides, both serving as sources of additional income.

The benefits that can be derived from conservation of wetlands are abundant. Healthy wetlands also help us cope with extreme weather events, by acting as natural safeguard against disasters. They provide humans with resources to sustain lives. In the advent of development, it is hoped that people and industries present in the delta will come together to help conserve the wetlands, and in any case, develop this important wildlife habitat sustainably.

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