The mangrove marathon walk

We packed ourselves in a matatu, driving to the southern edge of Mombasa where we would board the Likoni ferry. I was drenched in sweat and grateful that the windows in the back were openable (the American passenger vans I know have NO ventilation in the back). But, as we slowed to a halt waiting to drive onto the ferry, I was warned that I should close the window in case someone tries to snatch something from my hand...or sell me something. Indeed, several people moved between the cars on foot selling Coca-Cola beverages and other snacks. This man, below, tried to sell us bagged nuts but there would be no takers.





Our driver would have to pay to get on the ferry, but it costs nothing to walk on.





Back on continental Africa, we continued our drive south, passing several street-side vendors selling produce, clothes, rubber slippers, and other stuff.





And we drove further south, passing roadside businesses like these.

After a while, the roadside businesses stopped appearing and villages were spaced further apart. If we kept driving, we'd end up in Tanzania but we made a left long before that happened, through some bushes, and past a coconut grove that buffered Gazi Village from the road. Village children ran to us, excitedly yelling Jambo! Jambo! (hello!) as we found our way to our rooms. The wood walls and roof, tile floors, paved courtyard area, porcelain sink, flush toilet, and fully plumbed shower made it easy to feel like privileged royalty.

We regrouped soon after settling in, and sat for a brief introductory lecture with Kairo, a charismatic researcher from the Kenya Marine and Fisheries Research Institute. Mangroves, he explained, are trees that grow where most other things can't - in the intertidal zone, between land and sea.

These trees are able to survive, even thrive, in tropical saline environments that would quickly kill most other plants. This is accomplished by one of three elusive mechanisms:

1. Excretion - Plants take in salts along with water and excrete them to leaf surfaces. If you lick the back of a leaf that does this, it actually does taste salty.

2. Accumulation - Plants have established an unusually high tolerance for salt and store them in vacuoles.

3. Exclusion - Plant roots repel salt uptake. Studies have shown that near roots of plants that use this mechanism, salinity is measurably higher.

In addition to salinity, Kenyan mangroves are subject to anaerobic soil and tidal flooding, making survival even tougher. Unique adaptations enable mangroves to cope with this environment. "Prop roots" (the above ground roots in photo at left, for example), containing aerenchyma, are a common mangrove adaptation that provide a critical pathway for oxygen transport. Spongy "breathing roots" (pneumatophores) grow vertically, penetrating the soil surface, to enable oxygen uptake in water-logged soils where air is scarce.

Evert, a Dutch attorney and fellow volunteer, sinks knee-deep into oxygen deficient mud on our walk. The dark brown, almost black, color is a classic sign of oxygen deficiency. The sulfurous stench radiating from the ground and warm temperature of the mud are probably indicative of anaerobic bacterial activity which further verifies this.

This monkey stands amongst pneumatophores.

To me, mangroves look like weeds (in fact, they are in Hawaii). Perhaps this is why the scientific community has largely ignored the intertidal zone, instead favouring more glamorous rainforests at higher elevations and coral reefs at sea.

After Kairo's lecture, we set out for what Mark, the Scottish ecologist mangrove expert and Principal Investigator called "The Marathon Walk" -- a stroll along the village perimeter through the mangroves to see the wild adaptations first hand and get acquainted with the land.

As we passed village houses we learned that mangroves are the primary building material. I am not sure how these structures are anchored to the ground, but the next step is to erect the wall framing. This is done by lashing mangrove wood together in a grid pattern.





Then, the roof framing is constructed in a similar fashion, as can be seen in the background of the above photo. I remember seeing young girls sitting outside of houses around the village weaving roof thatch. They took a ~14" stick, weaving coconut fronds about it with some sort of raffia type material. These sections are then layered on the roof framing, and secured with, what I would call, twine.








They are overlapped to prevent water leakage, but in heavy rainfalls this is inevitable. The final phase is to pack the walls with mud and rock. Sometimes a rectangular area is left open to serve as a window. Even so, the windows are usually few and relatively small (presumably to maintain structural integrity). This, combined with the relatively dark color of the mud, makes for a dim interior even in broad daylight (in my very limited experience).





The village theater (above) is a great example of the finished product. Note the corrugated metal folded over the roof ridge - I expect this is to help keep water out. There is also a smaller piece of metal situated between the two roofs, acting as a rain gutter.

We continued on our walk and soon came upon a woman cutting and collecting mangroves for firewood, another traditional use of mangrove wood in Gazi.





Fishermen use mangrove wood to make poles (below). These poles, I assume, help them maneuver their solid wood boats if the water is shallow enough to push off the bottom. Some fishermen had wood oars (probably made from a larger hardwood tree) for canoeing (Indian style - no 'ama or 'iakos like the polynesian canoes as the hull is wider with a flatter bottom) in open ocean waters.

As we walked, tiny crabs scampered into their holes in the mud. There were at least two different kinds - a spotted one, and a dark brown/gray one.






Both had one oversized claw for fighting, as below, and a smaller one for eating. The crab expert wasn't in town, but I did learn that the crabs thrive in mangroves and are territorial - they will only go down another crab's hole as a last resort.

Fish also depend on mangroves for shelter from predators and food. And, this village depends on fish.

Unfortunately, man exploits mangrove directly for fuel and building material and also indirectly by claiming mangrove habitat for other uses (urban development, etc.), contributing to water pollution (oil spills, sewage effluent, etc.), and contributing to sea level rise via climate change.

This Earthwatch Expedition began as an effort to reforest denuded coastal land in Kenya. Reforestation was successful and the project evolved into a brilliantly efficient research project with social, economic, and environmental benefits.

The project objectives are to (1) quantify any impact mangroves have on mitigating soil erosion, (2) better understand the relationship between mangrove and fish and crab species, (3) explore the effects of species diversity and density on ecosystem productivity, and (4) determine a method for predicting below-ground root mass to investigate the viability of mangrove as carbon sink.

Findings will provide a better understanding of the complexities of these intertidal forests and the creatures that depend on them. Research results will hopefully provide information necessary to create a sustainable management plan to enable local communities to continue their traditional use of mangroves without depleting the resource. Restoring wetlands is like trying to glue a broken vase back together - it will never look the same and you're probably missing a few pieces - so it is important that we also focus on preserving mangrove forests. This project has developed community buy-in essential to resource preservation by creating research and other job opportunities for locals.

A group of women built this boardwalk through a mangrove forest and give educational tours. I'm not sure if they were inspired by the Earthwatch project or by a group of women from a neighboring village that also have a mangrove boardwalk attraction.

Next: Field execution of project objectives