Mangrove to Seagrass, a journey into Thailand’s coastal ecosystems
By David Matyas, MAP Volunteer Intern
During a two month immersion into the mangrove world as a volunteer with the Mangrove Action Project in Trang, southern Thailand I learned there are more than 60 species, they livelihoods for local communities, play a role in coastal protection, and have been greatly reduced in Thailand, mainly due to shrimp farming … It is indeed a unique ecosystem which has had so much research on a whole range of different kinds of issues and many books have been written about this magnificent forest. Some people have even devoted their entire life to protecting it.
Personally, I needed time to step back and explore something else.
Dr. Barry Bendell monitors seagrass on Koh Phra Thong an island off the coast of Phang-nga Province, Thailand. He is one of MAP’s volunteer scientific advisors, which is how I got in touch with him.
So, on Wednesday 22nd of June with the big Spring tides approaching — it was time to monitor seagrass — So I hit the road to meet him.
It was a long journey from the south to the north along the Andaman sea’s coast, taking me from Trang, through Krabi, past Phuket island to Phang-nga province, which by the way has the largest mangrove area in all Thailand.
Around Trang, it’s mainly flat and rolling land with oil palms and rubber tree plantations where a few limestone walls pop-up in the scenery, especially along the coast. Then, on the way, more and more cliffs unveiled themselves from Krabi to Phang-nga, a small mountain range of karst limestone emerges. Passing Phang-nga town, it becames more hilly and the winding road is surrounded by tropical rainforest all the way to my final destination for today: Kuraburi located on the main coastal road with a few houses and shops lining both sides.
Buses as well show a contrast between north and south on the Andaman coast. A comfy large seat in a fast AC bus from Trang to Phang-nga and then an old, orange painted, Mercedes-Benz bus, with benches as seats, open windows and fan on the ceiling, cruising at 30km per hour on average, struggling to get at the top of the hills.
I arrived just before nightfall to meet Barry We had a good dinner near the bus station, a cold beer and then we went to bed early. Early morning was announced to catch a boat to the Island.
In the morning, after a rice porridge and some purchases at the market, we went to the Kurburi pier. No boat was leaving to the island so we travelled to a second pier. Waiting for our boat, we were watching three local boats being filled up with sacks of concrete. The loaded boat’s gunnels were riding just above sea level and a small wave and some rains would be enough to sink them. Kind of laughing about the danger these people take, we were astonished when we understand that these were the only boats available to reach the island today.
|Our long-tail boat to Koh Phra Thong|
I took time to contemplate the mangrove forests. Young trees, sometimes an area with much diversity but mostly Rhizophora. Getting close to Phra Thong (Golden Buddha) Island I could see seagrass beds, mudflats, then mangrove and forest. A continuous natural setting. Why should we just protect the mangrove? Actually all this nature which we divide into units forms one large interconnected ecosystem.
|Navigating through the mangrove forest|
Afternoon arrives and we head to Tha Pae Yoi, the main village on the island from where we took a kayak and glide onto some sandbanks where seagrass was growing.
Time to learn more about the seagrass ecosystem.
Invisible at high tide, seagrasses, are a type of submerged aquatic vegetation. Many people confuse seagrass and seaweed which are quite different. These plants evolved from terrestrial plants and have become specialized and are able to live in the marine environment. They have leaves, roots, flowers and seeds like any terrestrial plants, but amazingly they can live covered with saltwater most of the time. Salt kills plants and being submerged underwater means the lack of oxygen would drown plants.
Seagrasses are the foundation species for the system with a single acre (0.4 ha) of seagrass producing over 10 tons of leaf biomass per year. Seagrasses support the associated ecosystems of coral reefs and mangroves by providing food, shelter, and essential nursery areas to fish species (especially juveniles), countless invertebrates like crabs, shrimp, mollusks or sea cucumber and mammals like the dugongs who need more than 40 kg of seagrass per day. Seagrass meadows also provides livelihood for local communities. I was amazed by the number of people at each low tide collecting and harvesting conch, mussels, crabs and sea stars in the seagrass ecosystem. This not only provides food but also medicines and soil fertilizer for their gardens. Furthermore, seagrasses have a role in stabilizing sediments and improving water quality.
Barry is interested in a fair amount of research about invertebrate and seagrass. During the afternoon, we searched for a species of conch, an edible sea snail that people harvest, called dog conch. We collected all of them, both the small ones and the adult ones to measure them and then we released them. Barry took measurements of the adults as he is interested in the proportion between juvenile and adults in a seagrass area unprotected and protected.
As fresh air arrived as suddenly as the winds picked up, I looked at the horizon. A curtain of rain was moving down on us. A moment later, heavy rain and lightning ended our field work for the day. We paddled hard in the cold rain to reach the shore then it was a long motorbike drive back to our base in the village. The hot coffee was a fair reward.
Low tides were in the afternoon. In the morning, between down pours, I explored the Island. Koh Phra Thong is situated in Phang-nga province on the north-west coast of peninsular Thailand. It’s a flat and sandy island surrounded by mangrove on the landward side and beach facing the open Andaman Sea into the Bay of Bengal. On the western seaward side, beach forest with pine like trees (Casuarina equisetifolia) and in the island interior, a landscape with tall grasses and paper bark tea tree (Melaleuca quinquenervia) depicts this unique savannah ecosystem, not found on any other island along the Andaman coast.
|Savannah in front and behind, Casuarina trees hidding the ocean view|
|Pa Nee helping us with the seagrass monitoring|
There are disadvantages though. Usually, there is no clear end point for the monitoring and the objectives can be vague, and so it can be difficult for a funder to support long-term monitoring.
The Seagrass Watch monitoring uses the same method worldwide which consists in three transects of 50 meters each. Every 5 meters we dropped our square quadrat (50cm x 50cm) to sample everything from crab holes to any kind of invertebrates. Then we estimate the total coverage of seagrass and the coverage by seagrass species and finally record the length of the long seagrass.
During the next couple days, we sampled a second site, situated in a locally protected area (LPA). More seagrass was present and we could find bigger conch. The site is located just in front the village where local people support the idea of a seagrass conservation zone. Barry asked people in a survey about the protected seagrass area and everyone thought it was a good idea and many people certified that the number of conch has increased where they collected them outside the LPA. They feel the protected conservation area is acting as a nursery which is the primary purpose of a LPA.
Although a few people have helped on occasion with monitoring, most people are not really involved in any direct way although they think it is a good idea. They really just want to be able to collect conch for local consumption and to increase their incomes. I think it is the same in most places that people support conservation but only a minority gets involved.
Barry is also involved in sea cucumber raising in old extensive ponds2. I helped him to collect some young juveniles that can be stocked for grow-out in peace. At nightfall, we tried to monitor big sea cucumber in the protected area but the water was too turbid and we could hardly see anything except small fish and shrimp attracted by our lights.
On the way back to Trang, proceeding as on the way I came, I had plenty of time to think about restoration and ecosystems at much larger scale. Living in a small village with no electricity and few possibilities to earn an income I understand the needs of local communities which harvested the natural ecosystem for food, livelihood and money. A week of insertion into the local environment was indeed a rewarding experience. I regained my confidence in the need to protect the natural ecosystem and the importance of developing a holistic approach to understanding the complexity of the ecosystem, but also not forgetting the needs and benefits of resources for the local communities.
- Smithsonian National Museum of Natural History : http://ocean.si.edu/seagrass-and-seagrass-beds
- Rufford foundation, Barry Bendell’s project http://www.rufford.org/projects/barry_bendell