Palo Verde, pt. 5: A mangrove excursion

At 8 am on Friday, 3/4 we left Palo Verde for a trip to a mangrove forest! It took us several hours to get there, and then we hiked in through private property, ducking under barbed wire fences to cross some pastureland before arriving in the mangroves. It was amazing how quickly we transitioned from open fields to regular shrubs and trees on a forest edge to a full-on mangrove forest with almost exclusively mangroves growing there.

Mangroves are a paraphyletic group of trees that have all evolved adaptations to deal with high salt content in their water, poor nutrient availability in their soil, and occasional to frequent flooding caused by tidal changes. Mangroves live in coastal tropical and subtropical regions, in places where salt marshes would exist in temperate zones. The first type we encountered was the black mangrove, which is the least salt-tolerant species that we saw and thus lives farthest inland. The trees look relatively normal, except for the fact that they send up short above-ground roots called pneumatophores which help with gas exchange when the tide comes in and the area is flooded.

Pneumatophores covering the ground of the black mangrove forest

Also, they deal with high salt levels by excreting it on the bottoms of their leaves! They excrete so much salt that you can see the crystals on the bottom, and if you lick the leaves you can taste it. Tom described it as having the same amount of saltiness as a pretzel, which I would agree with.

Salty leaves of the black mangrove trees

After a brief introduction to the black mangroves, Mau gave us some time to sit in the forest and observe our surroundings. We then talked about the main differences we noticed between the mangrove forest and the other tropical forests we'd seen, and determined that the most striking one was the lack of biodiversity in the mangroves. They are literally the only plant species in sight, with no groundcover or subcanopy growth whatsoever. The only animals we saw were fiddler crabs, which burrow holes into the salty mud... none of the birds, lizards, frogs, or monkies that we'd been seeing at other sites.

One of the many crabs we saw

Aside from a few mosquitoes (which are apparently much more abundant in the wet season) and some termites, we didn't even see any insects! Also, the forest structure is much simpler with a relatively uniform canopy height and really no other layers of foliage.

Nothing but black mangroves, as far as the eye can see.

We kept walking towards the coast (over the pneumatophores, which make the mud feel bouncy when you step on them!) until we got to the red mangroves. Because they are more salt-tolerant, they live closer to the water, which means the mud there is REALLY wet! This was one of the first hikes that I felt like my rubber boots were truly necessary, and I was glad I had worn them. There were some places where you could unintentionally sink in up to your knee in mud, and that happened to a few people while we were entering the red mangrove zone. Red mangrove is the type of mangrove that you probably think of when you think about mangroves in general, because they have the very distinctive prop roots that are easy to remember.

Red mangroves

Hiking through a red mangrove forest is not an easy task, since on top of the mud you have to climb over, under, and around all of the crazy above-ground roots of the trees. When we had gotten far enough into the forest, we stopped for lunch, which we had packed in with us that morning. We were all hot and sweaty, but it was pretty neat to eat a sandwich while perched five feet above the ground on a giant tree root.

Hiking through the red mangroves felt like spy training in the movies when you have to cross a room secured with laser beams, you know?

After lunch we talked about the red mangroves a bit, and then split up into small groups to do an activity. Our professor had brought a lengthy review article about mangrove ecology, and split it up into sections so that each group could read a small part and then present it to the class. My section was about the importance of mangroves in the fishing industry, since many young fish hatchlings use mangrove forests as a sort of nursery, since the water is calm and protected and there is an abundance of food. After discussing the article, we all wrote down some short ideas about how to restore mangrove forests, since many of them have been destroyed worldwide for coastal development and flood management, and then started to head back because the tide was coming in! It started while we were presenting our article sections, and happened really fast. Again, I was glad to have my rubber boots! We all trekked out through several inches of water, which made the mud even sloppier.

The tide coming in and flooding the forest!

At one point my foot sank in to below boot level, so my boot filled up with muddy water that splashed all over my pants when I tried to dump it out. By the time we made it back to the bus, I was basically completely soaked, but still in awe of the mangrove forests. It was an amazing ecosystem to see, and unlike anything I have ever experienced before, in Costa Rica or elsewhere. I changed into my extra pair of shorts on the bus, and we drove another hour and a half to get to the field station where we were spending the night.

We arrived at 5, and discovered that we were staying approximately 4 blocks away from a beach! Mau didn't tell us this in advance, so of course none of us had brought bathing suits or other beach-appropriate things. We were so excited to be at the beach (for the first time since we'd arrived in Costa Rica!) that we all went anyway, me in my hiking boots since I didn't even bring flip-flops for the one night trip.

First glimpse of the beach across the street from our station

Sunset!

Sunset + amigas!

We went swimming in our clothes right as the sun was setting, and swimming out about 100 feet in the calm cove we could actually see the sunset which you couldn't see from land. The water was warm, the sky was beautiful, and we were all incredibly happy. Going to the beach is almost always relaxing, but the stress of our independent projects and the surprise of not knowing we were going to the beach made our 30 minutes in the water that much more enjoyable.

We returned to the station for dinner as it was starting to get dark. I had only brought one extra pair of shorts since the trip was so short, which I had worn swimming, and my field pants were still soaked with muddy water from the mangroves. I was mentally readying myself to wear a bedsheet until my clothes dried the next day, but right before dinner Chesca lent me the shorts she had brought to sleep in. We were supposed to have a class that night, but our professors rescheduled it for the next morning so we had the evening free. Some people stayed up to have a fiesta, but after sitting around and talking for a bit I was completely exhausted and went to bed at 9 pm. I had been awake since 4:45 am the day before, working on IP things the whole time and then leaving straight for the mangroves without sleeping the night before. Going to bed that night felt amazing, and I slept for 10 glorious hours.

The next morning we had a lecture after breakfast on mangrove ecology with a visiting professor who had studied mangroves extensively. Much of the class was a review of the things we had seen the day before, but I enjoyed it because I found it all very interesting the first time. After class we had free time until lunch, so of course we went back to the beach. My pants were still not dry from the day before, so I had nothing to change into if I went swimming. I enjoyed the beach from dry land, though, and hung out in the sun for a few hours, heading back to shower before lunchtime.

Back to the beach in the AM!

Strollin'

Quite content to be at the beach

On the way back to Palo Verde, we stopped at "Megafauna Park," which is basically a tourist trap on the side of the road somewhere near the coast. You pay admission to walk around a trail with giant cement sculptures of large animals of Costa Rica, both alive and extinct. It was kind of a joke thrown in by Mau since we had spent so much time talking about gomphotheres, a group of extinct megafauna, in Palo Verde. We spent about two hours there looking at the poorly-made, disproportionate, and probably scientifically inaccurate sculptures, often times imitating their expressions ourselves since they all looked slightly crazed.

The T-rex that guards the entrance to Megafauna Park

Monkey face?

Tessa and an anteater

Patrick imitating some large animal that I don't recognize, and doing a fantastic job of it. Tyra would be proud!

This guy was FIERCE.

Patrick next to the giant ground sloth, which was grossly disproportionate!

Another crazed-looking cement statue

There was also a small insect museum attached to the gift shop, which was interesting because the insects were arranged in interesting patterns and hung like pieces of art.

Insect art

After our jaunt with the poorly-recreated megafauna, we finished our bus ride back to Palo Verde, arriving just in time for dinner.