Ran Nathan on the Growing Importance of Movement Ecology

Scientist Interview: October 2010

Ran NathanIn Essential Science IndicatorsSM from Clarivate Analytics, the work of Professor Ran Nathan ranks among the top 1% of scientists in the field of Environment & Ecology. His current record in this field includes 35 papers cited a total of 1,890 times between January 1, 2000 and June 30, 2010. One of his papers ranks among the 100 most-cited in the field.

Nathan is the Elected Chairman of The Alexander Silberman Institute of Life Sciences of the Hebrew University of Jerusalem, where he also heads up the Movement Ecology Lab, which is part of the Department of Ecology, Evolution and Behavior.

 
Below, NATHAN talks with ScienceWatch.com about his highly cited work

SW: Would you tell us a bit about your educational background and research experiences?

I graduated from the Hebrew University of Jerusalem at the same Institute of Life Sciences that I now chair. In my Ph.D. research, supervised by Uriel Safriel and the late Imanuel Noy-Meir, I worked on seed dispersal and seedling recruitment in Aleppo pine.

I then moved to Princeton to carry out post-doctoral research with Simon Levin, investigating the mechanisms underlying long-distance dispersal of seeds by wind. In 2001, I obtained a faculty position at Ben-Gurion University in Israel, and in 2003 moved to the Hebrew University.

My research merges fieldwork with modeling tools to elucidate various movement phenomena such as seed dispersal, bird migration, and animal foraging and navigation. In the last 10 years, I have led about 15 different research projects with a field research component in Israel and Panama (as a Research Associate in the Smithsonian Tropical Research Institute), and collaborated on field studies in Kenya, Namibia, and Australia as well.

SW: The bulk of your highly cited papers deal with seed dispersal. Is this the primary focus of your research?

The simple answer is "yes," but I have to admit my plans were different in the beginning and my current research is expanding beyond seed dispersal. In 1992, the last year of my undergraduate studies, I was interested in pursuing M.Sc. research on bird behavioral ecology and therefore did my guided undergrad project on the behavior of two lark species in different habitats in the laboratory of Uriel Safriel, the bird expert of the Hebrew University.


Tower Traps Mt. Pithulim.
 
View or download more images of Ran Nathan's work (see also).

Uriel suggested I consider deepening my training as an ecologist by studying the basic components of ecological systems, plants and their spatiotemporal dynamics, by combining modeling and fieldwork. This was just a few years after the big Yellowstone fires in the U.S.A. and the big fire on Mt. Carmel in Israel, when Uriel chaired a scientific committee assigned to guide the restoration of this region.

I was given the task of modeling plant dynamics in this area, and decided to start from the seed dispersal of a dominant tree species, Aleppo pine, that happens to be dispersed by wind. Seed-dispersal research has indeed turned out to be my main theme, and it is still one of the main topics being studied in my laboratory.

Yet, over the last years I returned to my original plans, and developed projects on movement of birds and other animals as well. In fact, most of the ongoing projects in my laboratory currently focus on movement of animals, and especially birds. But I am certainly not going to put seed dispersal aside, there are many interesting ideas and challenges about seed dispersal I wish to pursue.

SW: Your most-cited original article in our database is the 2002 Nature paper, "Mechanisms of long-distance dispersal of seeds by wind." Would you please tell us about this paper—its goals and its findings, and also why you think it's been so well cited?

This article describes the first exciting findings of my post-doctoral work at Princeton with Simon Levin and Henry Horn, supported by a grant from the US NSF. We were looking for ways to quantify and understand long-distance dispersal (LDD), and Roni Avissar, our partner from Atmospheric Sciences, arranged a visit to Gaby Katul at Duke University to see his experimental field setup at Duke Forest.

Gaby had no knowledge of seeds at the time but the project was interesting enough for him. Eventually, he became my main partner in wind dispersal research, and our joint work has been very pleasant and fruitful so far. Gaby is originally from Lebanon, I am an Israeli, and we are best friends.

This specific paper in Nature was the first to use a detailed atmospheric model that incorporates turbulence in three dimensions to simulate trajectories of individual seeds dispersed by wind. Because LDD events are extremely difficult to quantify, we replaced the common setting of seed traps on the ground by a vertical setup of 102 seed traps along a 45-m high tower, placed at 12 different heights including three levels above the tallest trees.

The model suggested that the key mechanism driving LDD is transport by relatively prolonged turbulent updrafts that can carry seeds above the forest where winds are stronger. Therefore, uplifted seeds are dispersed by winds over much longer distances than non-uplifted seeds within the canopy.

Data from the vertical array of seed traps showed that the model adequately describes the vertical component of seed dispersal. Many subsequent studies have shown that this is indeed the key process driving LDD by wind, in various other species and ecosystems.

SW: Why is seed dispersal so important to biodiversity conservation?

"..are the two movement phenomena that I study, seed dispersal and bird migration, really so different?..."

Seed dispersal is important to biodiversity conservation because it plays a major role in all the main processes currently threatening global biodiversity. These include changes in land use, habitat loss and fragmentation, invasive species, climate changes altering species distributions and the escape of genetically modified organisms (GMOs).

In some cases, like invasive species and GMOs, excessive dispersal is the core problem itself. In other cases, the problem is exactly the opposite: insufficient dispersal, as happens for example to many native species in fragmented landscape. This is true of plants, for which seed dispersal is the main movement process, but dispersal is incredibly important for the conservation of animals as well, essentially for similar reasons.

SW: In 2008, you were the lead author on aPNAS special issue paper about a paradigm for unifying organismal movement research—movement ecology (105[49]: 19052-9, 9 December 2008). Could you tell us about this aspect of your work?

I am very happy for this question because I consider this work on movement ecology my most important scientific contribution thus far. The idea of movement ecology was born in 2002. I was a first-year faculty member when this Nature paper on wind dispersal was published and my two new grant proposals, also on seed dispersal by wind, were approved for funding.

Yet, my first M.Sc. student, Ofir Altstein, was recruited to study seed dispersal by birds and my first Ph.D. student, Nir Sapir, launched a project on bird migration. I guess the birder in me was eager to study birds, not only seeds. This "mix", however, raised a practical dilemma: what name should I call my research group?

This has immediately led to more elementary questions: are the two movement phenomena that I study, seed dispersal and bird migration, really so different? And if they have something in common, and some key differences, how can we tell? Because we were most interested in studying movements of both seeds and birds and their interactions with the environment, I decided to call my research group "movement ecology." Later on I noticed this term has already been used in the literature, but very occasionally at the time and never in the context of a unifying research paradigm.

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