The Department of Environment and Natural Resources (DENR) was recently mentioned on UNTV News on 05-September-2017 as continuously pushing for the periodic planting of mangroves. DENR is targeting to plant mangroves in more than 50K hectares of swamps, especially in areas frequently hit by typhoons. DENR spends roughly Php50K per hectare as part of the National Greening Program to plant mangroves. Management of mangroves is a mandate of the Protected Areas and Wildlife Bureau (PAWB)’s Coastal and Marine Management Division.
Mangroves along the coastlines significantly decrease the dangers and havoc brought on by typhoons, storm surges, and tsunamis. Henry Adoraro, Director, Ecosystem Research and Development Bureau stated, “Mangroves provide shelter and protection to the community. In fact, study shows that a kilometer-wide of mangrove area can reduce the tsunamis by 70% when it comes to strength.”
DENR defines mangroves as a part of the coastal and marine ecosystem that includes seagrass and the coral reefs. Out of the world’s more than 70 salt-tolerant mangrove species, around 46 species exist in the Philippines. The mangrove is known as the “rainforest of the sea,” and like the inland rainforest, a mangrove provides both economic and ecological benefits to the coastlines. Mangroves are a source of alcohol, medicines, tannin, timber, and housing materials.
The link between land and the sea. The World Wildlife Fund (WWF) considers the mangrove forest as a bridge between terrestrial and marine environments, and as a productive ecosystem. Mangroves transfer organic matter and energy from land to sea, forming the base of many marine food sources. Mangroves are thus home to terrestrial and marine life. Mangroves also play a vital role in trapping and filtering sediments, which help protect coastlines. Since mangrove forests grow where saltwater meets the shore in tropical and subtropical regions, they serve as an interface between terrestrial, fresh-water and marine ecosystems.
With the mangroves’ distinctive stilt and prop roots extending from the trunk, mangroves thrive in areas of soft, waterlogged, and oxygen-poor soil by using aerial and horizontal roots to gain a foothold in the soil. The roots absorb oxygen from the air, and the tree leaves expel excess salt. A multitude of aquatic and salt-tolerant plants also grow within the mangrove forests.
Mangrove ecosystems are most diverse in South Asian seas and least diverse in Caribbean seas. Mangrove forests can roof a number of endemic bird species that are endangered. But apart from the natural and human threats, Mangroves require relatively intact hydrographic and salinity regimes. Without these conditions, the propagation or conservation of mangroves is difficult or next to impossible to achieve.
Mangroves are susceptible to pollution, particularly oil and petroleum-based compounds; and a change in salinity levels can have a dramatic impact on the mangrove forest.
Mangroves in the Philippines. In 2013, global Landsat imaging done from 1990-2010 by Jordan B. Long of EROS and Chandra Giri of ARSC, both of which were contractors of USGS in South Dakota, published in the Journal of Coastal Research, the estimated total area of Philippine mangrove coverage at 256, 185 hectares in 2000, which was a bit higher than DENR’s estimate of 247,362 hectares in 2003.
The report finds 66 out of 82 (80%) provinces have mangroves; and identified the top provinces with the most mangrove areas as a percentage of total national area: Palawan (22.2%), Sulu (8%), and Zamboanga del Norte and Sur (9.86%); Surigao del Norte and Sur (6.8%), Eastern and Western Samar (6.1%), Quezon (5.5%), Tawi-Tawi (4.4%), Bohol (3.69%), and Basilan (2.97%). About 49K hectares (19%) of total national area is protected by IUCN for long-term conservation purposes. These protected mangroves are in Palawan, Siargao, Malampaya Sound, Biri Larosa, El Nido, Tanon Strait, Northern Sierra Madre, Dumanquilas Bay, Sibuyan Islands, and Calauit Island.
Importance of Mangrove ecosystem services:
- Fisheries: The mangrove forest is home to a large variety of fish, crab, shrimp, and mollusk species. These fisheries form an essential source of food for thousands of coastal communities. The forests serve as nurseries for coral reef fish and other fish.
- Timber and plant products: The mangrove wood is resistant to rot and insects, making it extremely valuable. Many coastal and indigenous communities rely on this wood for construction material, firewood, wood chips, pulp, and charcoal. These communities also collect medicinal plants from mangrove ecosystems and use mangrove leaves as animal fodder.
- Coastal protection: The dense root systems of mangrove forests root systems trap sediments flowing from rivers and off the land. Trapped sediments help stabilize the coastline and prevent erosion from hurricanes, high waves, storms and floods. And by filtering out the sediments, the mangroves protect coral reefs and seagrass meadows from being smothered in sediment. In areas where mangroves had been cleared, coastal damage caused by natural disaster is much more severe.
- Tourism: Given the diversity of life inhabiting mangrove systems, and likely proximity to other tourist spots such as coral reefs and sandy beaches, it is surprising that only a few countries have tapped into the tourism potential of their mangrove forests. Bicol and Palawan offer snorkeling expeditions in and around mangroves to witness a variety of fish against an enchanting scenario of interwoven roots delving deep into the sand. Potential revenue generation lies in tourism with on-site learning about mangrove forests.
Threats. The mangrove forests are one of the world’s most threatened tropical ecosystems. More than 35% of the world’s mangroves are already gone. The rate of disappearing mangroves in this century is up to 50% in countries such as India, Philippines, and Vietnam, while in the Americas they are being cleared at a rate faster than tropical rainforests. Although natural disasters are big threats, man-made pollution is the biggest threat to mangroves. The threats include:
- Clearing: The mangrove forests are being cleared to make room for agriculture, human settlements, and infrastructure such as piers, airports, industrial zones, tourist developments, aquaculture, and salt farms resulting in major mangrove loss.
- Overharvesting: Over-harvesting mangrove trees have taken place for centuries and it is no longer sustainable, threatening the future of the mangrove forests.
- River changes: Dams and irrigation reduce the amount of water reaching mangrove forests, changing the salinity level of water in the forest. If salinity is too high, the mangroves cannot survive. Diverted freshwater can lead to mangroves drying out. Increased erosion due to land deforestation can massively increase the amount of sediment in rivers. This affects the mangrove’s filtering ability, leading to a dying mangrove forest.
- Overfishing: The global overfishing crisis facing the world’s oceans also affects the ecological balance of the food chains and mangrove fish communities.
- Destruction of coral reefs: Coral reefs are home to 25% of marine life and simultaneously provide the first barrier against currents and strong waves. When destroyed, the stronger-than-normal waves and currents reaching the coast can undermine the fine sediment where mangroves grow. This prevents seedlings from taking root and washes away nutrients essential for mangrove ecosystems to flourish.
- Pollution: Fertilizers, pesticides, sewage, and other toxic man-made chemicals carried by river systems from upstream sources can kill animals living in mangrove forests, while oil pollution can choke mangrove roots and suffocate the trees.
- Climate change: The mangrove forests require stable sea levels for long-term survival. Coastal habitats are already getting flooded and corals bleached. Rapid sea level rise will likely be the greatest climate change challenge to mangrove ecosystems.
IUCN: Mangrove forests in worldwide decline. More than 1 in 6 (17%) mangrove species worldwide are in danger of extinction largely due to coastal development, climate change, logging and agriculture, according to the first-ever global assessment on the conservation status of mangroves for the IUCN Red List of Threatened Species. As a result of the assessment, 11 out of 70 (16%) mangrove species have been placed on the IUCN Red List.
Mangrove forests are vital to coastal communities as they help protect against damage caused by tsunami waves, erosion and storms, and serve as a nursery for fish and other species that support coastal livelihoods. In addition, they have an incredible ability to seize carbon from the atmosphere, and serve as both a source and storage for nutrients for inshore marine habitats, such as seagrass beds and coral reefs.
“The potential loss of these species is a symptom of widespread destruction and exploitation of mangrove forests,” says Beth Polidoro, Researcher and Principal Author, Global Marine Species Assessment Unit, in a joint study with IUCN and Conservation International. “Mangroves form one of the most important tropical habitats that support many species, and their loss can affect marine and terrestrial biodiversity more widely.”
“The loss of mangroves will have devastating economic and environmental consequences,” says Greg Stone, Senior Vice President, Marine Programs, Conservation International.
“These ecosystems are not only a vital component in efforts to fight climate change, but they also protect some of the world’s most vulnerable people from extreme weather and provide them with a source of food and income,” Stone adds.
Hanneke Van Lavieren of United Nations University said, “There is now a growing awareness of the importance of mangroves, and government and community-led efforts are under way to restore or replant mangroves, and to improve legal systems to regulate future use.”
As DENR’s PAWD takes the lead in propagating mangrove forests in the Philippines, let us find a way to lend support to this cause by joining mangrove tours to help our local coastal communities purchase mangrove seedlings and restore their mangrove forests.