Deploy in mangroves

The first two days went very well, so we moved ahead. On the third day, we started on a small river between the Sundarbans mangroves and the settlement, watching monkeys play on the shore at the edge of the forest. On the settled side, we found our clearing. At this site and the last few sites before, some of the paddy fields were recently planted with watermelons. The best watermelons in Bangladesh are grown in this area and their most valuable crop. Still, enough fields remain unplanted for us to be successful.

We found our first monkey on the shore of the forest.

The second site of the day was more problematic. We won’t be able to enter the Sundarbans until the next day, so we have to work on the last settlement on the Left Bank. When we headed to what we thought was fallow, it turned out to be a large construction site with backhoes moving around imported sand. After what seemed like an eternity in the hot sun, we finally found a spot in two dry rice fields that was far enough from heavy machinery to get a good measurement. By the time we finished, it was too late for the third stop. Still, I’ve traveled nearly 7 miles for both locations.

Our team traveled to a location on a country boat with gear and guards.

In the evening, the speedboat went to Mong La, sent Anwar and an accompanying reporter, and picked up Céline Grall and Sanju Singha. She is my former postdoc and is bringing in additional scientific measurement equipment. Sanju has collaborated extensively with me on my GNSS (GPS) work. We will visit two sites later on this tour.

We’re used to a routine of 6:00 breakfast, pickup and deployment, 12:30-1 lunch, more deployments, and 7:30 dinner. The food is a buffet like the lunch seen here.

To save time, we split our site searches in the morning. I took the speedboat back to the first stop and the country boat took people to the second stop. On the way back, we picked up our two rangers and got permission to work in the Sundarbans mangroves. With only two sites to choose from, we were ready to start the deployment early and successfully installed 4 sites.

Our speedboat engine failed and had to be towed to a ranger station by a country boat, and our crew managed to fix it.

Deploying in the Sundarbans, the largest mangrove forest in the world, is not the same as working in a densely populated area. We just have to pick a location at the correct distance downstream and enter the forest. We hiked through the bushes using deer trails whenever possible and tried to find enough clearing to set the central receiver location. For the magnetometer, the challenge was to find a point in the correct orientation without the roots, especially the aerial roots that allow mangoes to live in salt water.

Nafis uses a compass to guide the person deploying the electrodes, while he can still see them.

The electrodes are now the slowest part of the deployment. Had to go straight N, S, E or W, we couldn’t follow the trail and had to go straight through trees and brushes. We also couldn’t see 50 m through the forest, so more creative ways of locating the electrodes had to be found, such as having the middleman use a compass. For distance we need to use a tape measure as laser rangefinders don’t work. We also needed an armed guard to go to the electrodes with the team due to the danger of tigers. On the last stop of our first day we came across pugmarks – tiger footprints – probably from that morning. We saw some old pugmarks on about 1/4 of the site.

We went through some dense forest to reach our site.and low golan Forests are even worse.

Nonetheless, we managed to install 4 sites in Sundarbans on day one. Just pulling 2 sites from the previous day gives us more time to install new sites. The next day was the opposite. We had to pick up 4 stops. We could split into two groups by picking up two more rangers, but they had to return to their station after the pick-up.The afternoon passed slowly because golan The various mangroves at the site form a very dense forest. We had to hack our way with an axe.

Install vertical magnetometers at the roots of spiky aerial mangroves.

Since tigers like this kind of forest, we have to be extra careful. Our staff made loud noises to help keep the tigers away. Since there are many deer here, the tigers in this part of the Sundarbans are not very ferocious and the noise is enough to keep them away. At least, we hope so. Almost all tiger attacks are further west than where we work. Nonetheless, we have established clear safety protocols. Each person should be in groups of at least 4 people with armed guards. We make sure we have everything we need because one can’t go back alone and pick up what’s been forgotten. We keep making a lot of noise.

Sanju’s hand is next to a tiger mark we found.

Once a day, we also deploy a gravimeter from Céline and a precision GPS of mine. While the GPS accuracy for all trees will be low compared to my geodetic work, it’s accurate enough for gravimetry. Normally, Sanju and I set up the GPS, while Céline handles the gravimeter, all guarded by an armed guard.

Céline took the gravity measurements next to our makeshift GPS antenna mount and instrument case, while a guard kept watch over us.

We had wished there were 4 guards with us instead of two. However, most of the time we were able to get a third (and fourth) guard. Like Bangladesh, we adjust our schedule based on the difficulty of the site and the number of guards we have. Some days we can split up to retrieve instruments faster. One group traveled further afield by speedboat, while country boats and Kokilmoni covered other locations.

One morning, we discovered that one of our magnetometers had been dug up by a wild boar. Fortunately, we logged enough data before it happened.

At night, after field work and showers, we watched wildlife in the forest until dark. We’ve seen deer, crocodiles, wild boars, egrets, storks and monkeys – but no tigers. We stayed two nights in one of my favourite places in the Sundarbans, near the Kokilmoni place where our boat was named. Smaller passages allow us to see beautiful views of both sides.

Our group emerged from the forest after successful instrument recovery.

We took a group photo at a location in the Sundarbans.

I am also learning to distinguish between different mangrove species.We try to avoid dense golan Forests, prefer more open ones Gwa or Sundari Forest. Our maps don’t differentiate between forest types, so we sometimes cruise along the coast looking for more open forest. At one location, we unsuccessfully took the country boat to a tidal creek in search of more open forest. At the last site in the Sundarbans, near the Bay of Bengal, we deployed on the lightly sandy tidal flat. It shouldn’t be flooded until the big tide in a few days, but we put the recorder and batter in a plastic bag on top of the metal box, just in case.

Arriving at low tide, we struggled through thigh-deep mud to the forest at this location.

The tidal creek was lined with Golpata palms, and we failed our voyage to find more open forest.

On our last morning in the Sundarbans, we were delayed by thick fog. We had to wait for the fog to clear before we could get the last 3 sets. The speedboat crew headed to the last site found the recorder and magnetometer with a slight rise to stay dry, although some electrodes were underwater, which was fine. In the end, we completed 12 MT stops in four days in the Sundarbans. We then drove through the Sundarbans to Barisal and finally enjoyed most of the day during the transit.