Crystal McMichael is an Assistant Professor in the Department of Ecosystem and Landscape Dynamics at the University of Amsterdam. Her research interests are focused on assessing long-term (100s to 1000s of years) ecological processes in tropical ecosystems, and how distributions of species (including people) have changed over those time scales.
Crystal is particularly interested in how tropical ecosystems have responded to past disturbance events, including climatic changes (i.e., drought) and past human activities (i.e., fire and cultivation). Current research topics include reconstructing fire and vegetation histories across northwestern Amazonian and Andean landscapes, modeling changes in the distribution of people in Amazonian and Andean landscapes over the last 14,000 years, and determining whether past human activities left lasting ecological legacies on tropical systems.
A random walk into the rainforests of South America
My professional career completely changed in 2007. At that point, I was an unhappy graduate student in Florida. I was working on a project that related changes in retinal structure and composition of the eye to changes in life history characteristics of sea turtles. The project was interesting enough, but I disliked the euthanasia and dissection of the turtles. In my second year, I was considering quitting my Ph.D., but then my teaching assistantship position was moved from Genetics to Community Ecology. It was there that I met Mark Bush, a Neotropical palaeoecologist. I didn’t know it at the time, but meeting him would change my life completely, and he would become the biggest ecological inspiration of my life.
I began to read about Mark’s research and palaeoecology in general, and after many long discussions, he offered me a PhD position in his lab. In my first year (2007), he took a group of graduate students (including me) to Ecuador for fieldwork. I got the chance to core lakes and collect soil samples in the lowland Amazonian forests (Photo 1) and on two islands in the Galapagos (Photo 2). As someone who had always loved exploring nature, this was a dream come true! Seeing the forests and the islands exceeded all expectations, and I loved the physical challenge of the expedition. We had to hike all of the equipment (100s of kilos!) in and out of a caldera to reach our target lake on the island of Genovesa in the Galapagos (Photo 3). Physically, it was the most difficult thing I had ever done in my life, and I had even been at the gym training with my close friend/colleague Dunia Urrego (Photo 4) in the months beforehand! But the feeling after we successfully obtained those sediments and got everything back to the boat was incredible…empowering and inspiring. I’ve continued to run field expeditions to the tropics of South America since that summer. Spending time in the forests and interacting with the local people has shaped much of my research over the last decade. Many of my proposals and manuscripts originated from scribbles on mud-splattered sheets of paper that I wrote while in the forest!
My Ph.D. tested ideas that were put forth in Michael Heckenberger et al.’s 2003 Science paper, “Amazonia 1492: Pristine forest or cultural parkland?” and in Charles Mann’s book (2005) “1491: New revelations of the Americas before Columbus”. These controversial works refuted the long-standing idea that Amazonian forests were virgin and pristine until Europeans arrived to the American continent. But then many scholars immediately leapt towards the other extreme. In one instance, it was suggested that “If one wants to recreate pre-Columbian Amazonia, most of the forest needs to be removed, with many people and a managed, highly productive landscape replacing it” (William Woods, as quoted in Romero, 2012).
This statement implies that most of Amazonia, which is ca. 6 million km2 in size, is simply ‘regrowth forest’ that had been cut down only a few hundred years ago. But most importantly, there were no empirical data to support this statement. The ideas put forth by Heckenberger et al. came from a few archaeological sites scattered across the vast rainforest – hardly enough evidence to claim that most of the trees in the forest had been removed. But this is only one example of many statements that were made with similar tones. Mark Bush and Miles Silman (who also mentored me during my Ph.D.) summarized the impact of these types of statements on conservation policy, particularly given the lack of any empirical data in their paper “Amazonian exploitation revisited: Ecological asymmetry and the policy pendulum” (2007). This paper paved the way for my Ph.D., so of course it had a huge impact on my early research.
Halfway through my Ph.D. (2010), I was awarded a short-term fellowship from Smithsonian Tropical Research Institute (STRI) to go and learn phytolith identification (silica microfossils used in palaeoecological and archaeological reconstructions) with Dolores Piperno, who was also on my Ph.D. committee. Dolores is a true inspiration; she is a member of the National Academy of Sciences, and wrote the books on phytolith analysis for palaeoecologists and archaeologists (Piperno, 2006, Piperno, 1988). I have learned so much from her, and we still work very closely together. While I was at STRI, I was also able to work with another person who has inspired my research: Joe Wright. Joe is one of the world’s leading experts in tropical forest ecology, and his 2005 paper “Tropical forests in a changing environment” suggested that the patterns observed in modern ecological inventories may reflect past disturbances originating from prehistoric people (i.e. fire and cultivation) or past climatic changes (i.e. drought events). This theme was, and still is, a focus of much of my research.
Basically, my closest mentors all came from different disciplines. Mark is a palaeoecologist, Miles and Joe are modern ecologists, and Dolores is an anthropologist, human ecologist and archaeobotanist. I also developed a keen interest in remote sensing and spatial analyses while I was a postdoc at the University of New Hampshire with Michael Palace. All of those disciplines still appear in my research, and approaching scientific questions with interdisciplinary datasets and analysis techniques is one of the things I enjoy the most in my work.
A more recent influence on my research was the paper on “Hyperdominance in the Amazonian tree flora” by Hans ter Steege, et al. (2013). This work suggests that only 227 of ca. 16,000 species compose half the individual trees in the forest, and thus only 1.4% of the total tree diversity (termed hyperdominant species) plays a disproportionately large role in the biogeochemical cycling of the Amazon rainforest. A large part of my research then became focused on addressing whether these patterns could result from past human disturbances, and whether hyperdominance patterns changed on timescales that exceeded ecological observation. One of the first papers to come out of this endeavor was mine and Mark’s (2016) paper in Journal of Ecology “Holocene variability of an Amazonian hyperdominant”, where we showed an example of one species, Iriartea deltoidea, had increased in its abundance mainly over that last several thousand years. The relative influence of prehistoric people versus increasing precipitation in shaping this pattern, however, remains unclear.
Iriartea deltoidea, a tropical palm species, is a long way away from the sea turtle retinas that I was studying in 2007. The random event where the university moved my teaching assistantship position into Mark Bush’s class gave me the opportunity of a lifetime, and I took full advantage of it. My mentors also inspired me to work hard during the process, and it has paid off. Almost twelve years later, I am still traveling to amazing field sites. I remain close with all of my colleagues from that first expedition in 2007 (Photo 4). I am working in a great university, and I am surrounded by colleagues (many of whom I also consider friends) and students, both in the Netherlands and abroad, who inspire me. As a whole, I feel like I have the best career anyone could ever ask for!
Crystal McMichael, Associate Editor of Journal of Ecology, University of Amsterdam, The Netherlands