Mangroves and their implications for conservationists

Several weeks ago, I had the opportunity to visit a mangrove with my fellow students and professors. The two-hour ride was slightly packed in the back of our transport van, making for some sore legs at the end of the ride. But after visiting the mangrove, I couldn’t be more pleased with the fieldtrip. From reading scientific papers about mangroves in while sitting in a mangrove to walking through the beautiful mazes of mangrove tree roots, the trip was an excellent introduction to this tropical ecosystem. Yet, something else has stuck with me about the mangroves, weeks after trudging through the malleable floor of soil.

            You see, mangroves have always been a hard sell for conservationists. Full of tall trees, there is a plethora of natural resources in this ecosystem. Furthermore, they are found on the edge of shores, which are often targeted by human activity. Add in the fact that their soils can release methane, and you have yourself a perfect target for habitat destruction.

            This poses a significant problem for those trying to protect these shoreline ecosystems. How do you convince individuals that mangroves are more than a pungent view disruptor? We discussed this as a class, and the most compelling argument for mangroves was that they protect inland areas from hurricanes. They are impressive buffer zones between estuaries and inland terrestrial ecosystems. Thus, removing these mangroves can severely endanger communities near shorelines.

            This facet of mangrove conservation has stuck with me, days after we trudged our way outside of the saline-rich forest. Conservation has a human element, and this human element cannot be ignored while trying to protect ecosystems. It may be selfishness or a facet of the human condition, but we tend to invest energies in causes that provide direct benefits. Accepting this is key to successful conservation endeavors.

            I will be the first to say that these mangroves are valuable and worth protecting in their own right; from the scurrying crabs to the towering mangrove trees, this ecosystem provokes respect and appreciation for natural beauty. But connecting this ecosystem to tangible human benefits is a valuable conservation strategy; spreading the word about its natural hurricane protection can be a really effective strategy! This could get local communities invested in conservation, which could extend to other ecological initiatives.

            This is an important facet that all conservationists must consider. While protecting species and their homes is a noble cause, there will always be the element of human activity implicated in conservation. My visit to the mangrove is a reminder that conservation only works if you empower the communities that will be affected by conservation policies. Fail to do so, and you won’t have much success in protecting those scurrying crabs, nor those magnificent trees.

Bryce Pepin, Tufts University

New passion for mangroves

On one of our days in Palo Verde, we hopped on the bus for a two-hour bumpy ride to a mangrove.  Mangroves have been the common example of environmental services used in my biology and climate change classes in high school and college.  I always had difficulty comprehending mangroves’ importance since I had never seen them in person.  A field trip that far away seemed a little perplexing considering we were in the midst of designing our independent projects, but seeing the mangroves definitely improved my understanding and appreciation for them.

            Mangroves are critical habitat for a variety of arthropods, fish, and reptiles.  Arthropods specialized in eating the salty leaves of the mangrove trees are their main herbivores.  Mangroves serve as a hiding place for immature fish away from their predators.  They also provide a habitat and food for a unique set of snakes, crocodilians, turtles, and birds either passing through or inhabiting the area permanently. 

            Mangroves also play a critical role in mitigating climate change and its effects.  In terms of carbon sequestration, mangroves take up and store more carbon than tropical ocean phytoplankton in a given area.  Mangroves also serve as buffers to tropical storms, which are increasing in intensity and frequency with climate change. 

            Mangroves buffer aquatic systems against human land use.  They hold soil in place, preventing it from flowing into rivers and increasing turbidity.  Mangrove trees filter through polluted water flowing to the river and also trap trash, preventing it from going into the ocean.

            These are just three of the many services mangroves provide.  Unfortunately, they are undervalued ecosystems.  Local communities do not like the smell of decomposition and the mosquitoes they harbor.  For this reason, they overexploit mangroves for charcoal and tannins and convert them to aquaculture areas.  Mangroves also sit near the shore, so coastline development has led to deforestation.  Hiking through the mangroves and learning how its system works gave me a unique perspective on its value and the importance of conserving them in tropical areas, especially as species extinctions, climate change, and human land use worsens.   

Ariek Barakat Norford, Franklin and Marshall College

Asking the wrong questions for the right reasons

Coming up with a research question might have been the most difficult aspect of the independent project assignment for everyone. Many people chose to start in the field, finding interesting study systems such as dragonflies and ant lions. The challenge of this approach, they found, was that many of their questions of interest were “patterns, not biological hypotheses”. My approach was different, but also full of challenges. I started by reading papers, quickly came up with a relatively unexplored question that I was excited about, and then spent the next several days struggling to find an appropriate study system in Palo Verde.

            I hoped to study preferences of different species of pollinators that visit the same species of flower. I knew that pollinator-mediated selection on floral traits was well documented among flower species. Hummingbird-pollinated flowers tend to be red and elongated; bee-pollinated flowers are blue or purple; bat-pollinated flowers are large and white. It’s not difficult to imagine how this works: pollinators tend to go to flowers that are easily visible within the color spectrum of the pollinator, or ones with a size and shape that facilitates nectar access for the pollinator.

            What I wondered about was variation within a flower species. I knew that some flower species are pollinated by multiple types of pollinators, and that even within a species, individual flowers can vary slightly in size, shape, and hue. I wondered whether pollinators that pollinate the same flower species might tend to visit different types of flowers, thus imposing non-random mating on the flower species. I’m very interested in mating system evolution, but previously, I had only mentally categorized mating system variation based on whether or not mating occurs: sexual reproduction, parthenogenesis, self-fertilization, haplodiploidy. I was interested in genome structures and evolutionary trajectory of populations, but I hadn’t been thinking about the ecological context that these mating systems occur in. And for flowering plants, one of the most important ecological drivers of mating patterns is pollinator behavior.

            I went out in to the field to look for a generalist flower species, and settled on Malvaviscus arboreus, a small shrub visited by bees, butterflies, and hummingbirds. But when I came back from the field and started reading papers about my study system, it turned out that the bees and butterflies did not pollinate the plant—they just drank the nectar. And Malvaviscus arboreus was also self-compatible, as it turned out, so any study of pollinator behavior would not accurately capture the reproductive events that were occurring.

            But while I was conducting field observations on the flower visitors that I thought were polinators, I noticed a few ants crawling in and out of the flowers. Could ants be pollinators? It didn’t seem likely that they traveled enough between flowers to transfer pollen. But luckily, I wrote down my observations in my field notebook. By the time I found out that Malvaviscus arboreus wasn’t the right study system for a project on preference differences between multiple pollinators—and I had spent too much time on this study system to start over again with another—I was already wondering what the ants were doing.

            I read about ants as nectar robbers and began to develop a new question: does nectar theft deter hummingbirds from visiting, since their nectar reward has been depleted? I had been interested in coevolutionary interactions—such as between mutualists, or hosts and pathogens—as a link between ecology and evolutionary biology. But it was new to me to consider how multiple ecological interactions could affect one another. In the case of nectar robbers, the antagonistic relationship between nectar robbers and the plant could affect the mutualistic relationship between the plant and its pollinator. As I read papers about complex species interactions, I learned that the ants that protect Vachellia (Acacia) trees from herbivory can scare pollinators away from the flowers. That was a case of one mutualism affecting another. I couldn’t understand the relationship between the plants and the hummingbirds without zooming out and considering the broader ecological context.

            I learned a few important lessons from this independent project. I had been interested in mating system evolution for a while, but I had only been thinking about mechanisms by which genomic material is inherited from the parent or parents. I hadn’t considered how ecological factors—such as assortative mating, sexual selection, and pollinator behavior—can influence which genomes recombine and contribute to future generations. I also learned that when I study an organism or an ecological interaction in the field, there is likely more to the picture than I initially realize. Any given species may have many mutualistic, antagonistic, or competitive interactions, and these interactions can influence one another. As I discussed in my blog post for Las Cruces, I am learning the importance of trying to figure out what might be going on in an ecosystem that I do not see.

            Lastly, I learned that it was okay to start out a research project by asking the wrong question—in this case, whether different species of pollinators have different floral trait preferences in a single flower species—because conducting exploratory fieldwork for the wrong question eventually led me to the right one.

Reena DeBray, Duke University