by Elaine Shen
**This piece is a shorter version of Elaine Shen’s essay, which was among the 2017 winners of the Greene Prize for Environmental Writing.**
“My Ph.D. advisor told me when I first visited Madagascar to be careful, because once you drink the water, you will be back,” Amy Dunham chuckled. “And she was right. It’s a naturalist’s paradise.”
For Dunham, assistant professor of ecology and evolutionary biology, the tropical rainforest is a home away from home. Her research sites, ranging from Madagascar and Gabon to the island of Guam, all boast highly diverse natural ecosystems as well as a rich culture celebrated by the native people who share their deep knowledge of the forest. Despite all of the scientific opportunities that such oases can offer, Dunham noted that there are few places left where such ecological treasures remain untouched by human development. With hunting, deforestation, habitat fragmentation, political instability and climate change threatening the abundant biodiversity in the world’s rainforests, Dunham’s research represents a last chance to understand the ecosystem shifts that are already underway. Through extensive collaboration with overseas research stations and intergovernmental organizations, Dunham is helping conserve these unique habitats using an approach that is not based on individual species, but is instead focused on preserving functional diversity. In other words, she is studying how the daily jobs of every species keep an ecosystem running smoothly.
One of the most important roles that animals play in tropical ecosystems is tree seed dispersal through various frugivores, or fruit-eating animals. Dunham explained that the extent of change that occurs from the absence of major frugivores is relatively unclear. The forests of Guam are interesting study sites for examining the role vertebrates play in the distribution of tree populations after its infamous ecological disaster in the 1940s. When a species of brown tree snake was accidentally introduced onto the island, it quickly became the top predator and eliminated 10 out of the 12 native bird species. The two remaining species are only maintained as a result of isolated and protected snake-free areas. Without the cacophony of birdcalls in the canopy, Guam soon became a silent forest, and the ecology of the area dramatically changed.
Some of the small birds that originally inhabited the area were frugivores, eating and dispersing the seeds of a majority of the island’s trees. They were especially important for pioneer trees, or the fast-growing trees that first populate open, sunlit areas in the forest and help stabilize the community after a natural disaster. If a seed of a pioneer tree does not reach a forest gap, it may never germinate or survive. Over the past three years, Dunham and a team of ecologists and students from Rice and the University of Guam have been working together to better understand the absence of such important seed dispersers. She and her colleagues are using observations, experiments and models to compare forests in Guam to the tree populations of nearby islands, whose bird populations remained intact after the introduction of the brown tree snake. So far, Dunham and her team have found that due to the absence of small birds in Guam, the tree gaps are increasing in size and pioneer trees are less successful in filling in the gaps. As a result, the entire composition of the rainforest is beginning to shift and change, demonstrating the domino effect in which one large-scale natural event can alter an entire ecosystem.
Another research site where the loss of critical seed dispersers is observed is in Madagascar, an island off the east coast of Africa, where Dunham is deeply involved in the study of lemurs, another group of frugivores. Lemurs are primates that are native only to Madagascar and resemble the earliest ancestors to monkeys and apes from 10s of millions of years ago. Ever since her undergraduate college years, Dunham has been enraptured with the huge lemur species diversity present in this Texas-sized country.
“By understanding how behavior and life histories have evolved and the forces that affect them, we can even begin to understand our own evolution,” Dunham explained. “After all, we are primates as well.”
There are currently 103 species of lemurs that live in Madagascar, representing over 20 percent of the world’s primate diversity. This group of primates exhibits female social dominance over males, an unusual characteristic for social mammals. In a groundbreaking study, Dunham found that female dominance in lemurs probably evolved over time in response to their unusual mating systems, resource competition, and the greater energetic demands faced by pregnant and lactating females. Lemurs also have very restricted breeding seasons, so small environmental variations can have a huge impact on future generations. Now, about 90 percent of lemur species are threatened with extinction. Dunham found that in addition to habitat loss and hunting, lemur populations are also sensitive to climate change. Increasing global sea temperatures causes wet seasons to get more extreme, resulting in a decrease in the fecundity, or reproductive capacity, of lemurs. Intense rainfall decreases the activity of lemurs, reduces forest fruit production, and has the potential to starve lemurs of the fruit they need to consume for lactating and caring for their offspring.
Similar to the small birds in Guam, Lemur populations are the main seed dispersers and are necessary to the functioning of the rainforests in Madagascar. In some cases, their generalist feeding behavior and consumption of the region’s larger fruits and seeds make them the only animal that can distribute them. With former graduate student Onja Razafindrastima and a team of 10 local villagers with extensive knowledge of the forest, Dunham was able to track 24 groups of lemurs over the course of a year. Through mathematical modeling, observations and experiments, the team estimates that the seeds of a common canopy tree are 300 percent more likely to sprout and become a sapling if dispersed by a lemur versus simply falling to the ground. Thus, like the silent forests of Guam, the absence of lemurs could lead to large-scale shifts in Madagascar’s unique flora.
Although her findings recommend an increase in rainforest conservation, Dunham recognized that it is not that simple. “The humanitarian and biodiversity crises in Madagascar are both so severe,” Dunham said. “The people are dependent on the wildlife, and the wildlife are affected by the people, so the two issues are hard to reconcile.”
To better understand the social and political aspects of conservation issues in Africa, Dunham joined the Intergovernmental Platform on Biodiversity and Ecosystem Services, a three-year project run by the United Nations that connects ecologists, social scientists and policymakers to create a global assessment of biodiversity loss and change and how it relates to human livelihoods. As part of the African Assessment, she contributes to this growing body of knowledge by providing a scientific perspective to African ecosystems. With this information, it is the hope that policymakers will be able to better prioritize and manage ecosystems and the services they provide to people. After joining last summer, Dunham is already discovering the challenges that African policymakers have struggled with for many years — an overall lack of infrastructure, communication difficulties and access to scientific information.
“My role is to translate science in an understandable and useful way to the world’s politicians,” Dunham said. “It is one of the most rewarding things I have done in a long time, because I am usually on the science side of things. This project allows me to collaborate with a diverse group of people, and it gives me a chance to use science to make a real impact.”
Both tropical ecosystems and conservation management are extremely complicated and inextricably intertwined. Dunham has been a part of the shift in ecosystem management and conservation biology that focuses more on the roles that animals play in the maintenance of biodiversity rather than individual species. Her research warns of community shifts as a result of anthropogenic and naturally induced stressors. The complicated networks and interactions between species mean that harming one species leads to detrimental changes in the whole ecosystem. In tandem to her research, Dunham’s involvement with interdisciplinary organizations shows her dedication to ensuring that advancements in ecological research leads to changes in conservation: without learning the ins and outs of policymaking, the prized regions that Dunham has spent so many years understanding will continue to deteriorate. Only through such diverse collaborations can large-scale changes productively preserve some of the world’s greatest biological treasures.
This essay first appeared in Enquiry: The Magazine of the Wiess School of Natural Sciences at Rice University. It is being republished here with the permission of both the author and magazine.
Elaine Shen is a junior at Rice University, majoring in ecology and evolutionary biology. She is a writer for Catalyst, Rice’s undergraduate science journal, and her article on overfishing is featured on the cover of the journal’s ninth volume. Shen is interested in marine biology, specifically fisheries management and the intersection of science and policy.