In this ScienceWatch.com interview, Dr.
Van Savage talks about his highly cited work in the
field of Environment & Ecology. According to a
recent analysis of Essential Science Indicators
Scientific, Dr. Savage’s work has entered the
top 1% in this field. At present, his overall record in
the database includes 23 papers cited a total of 865
times to date. Dr. Savage is an Instructor in the
Fontana Laboratory of the Department of Systems Biology
at Harvard Medical School in Boston,
Please tell us a little about your research
and educational background—specifically, how does a physicist
become involved in biology?
I have always enjoyed trying to solve problems that are simply stated yet
deceptively difficult. This process is especially exciting when I am able
to greatly simplify a problem by cleverly applying a few key insights about
the natural world. This fondness led me to physics, a field that has
focused on discovering fundamental features of the natural world, on
reducing those features to the most basic set from which all the rest can
be derived, and on devising new technical and mathematical tools that use
these fundamental features to solve practical problems. For example,
conservation of energy and momentum can be used to reconstruct a car crash
and even to determine which driver was at fault.
I majored in physics at Rhodes College and got a Ph.D. in theoretical
particle physics at Washington University in St. Louis, where my training
emphasized applied math approaches to problem solving. I received excellent
mentoring and advising from Dr. Bob MacQueen, Dr. Claude Bernard, and my
graduate adviser, Dr. Carl Bender. This training taught me the essentials
of problem solving that I was then eager to use to tackle the problems that
During graduate school I was fortunate enough to have a six-month
fellowship at the Santa Fe Institute (SFI), where scientists are encouraged
to explore other fields. As part of this fellowship I worked on allometric
scaling laws in biology with a physicist, Geoffrey West, and an ecologist,
Jim Brown. Together with their collaborators, these two were forging a
unifying approach to many biological problems. Their approach was strongly
grounded in empirical data and sought explanations using a modeling
philosophy similar to that of physics. I had always loved biology, and this
approach to biology was exactly what I had been searching for since high
"I want to identify which factors
constrain, organize, and control diversity in
ecological systems because I feel this will reveal the
fundamental features that shape the ecological and
evolutionary patterns we observe in nature."
I followed this graduate fellowship up by accepting a joint postdoc between
SFI and Los Alamos National Laboratory to pursue both biology and physics.
Within a year I found myself working almost solely on biological problems.
I was seduced by biology’s vast amounts of published empirical data,
and thus the many undiscovered and unexplained patterns lying dormant
within all those bound (and now online) journals. Reading the literature
and searching for data was like searching for treasure, and this stoked my
motivation to keep reading and learning.
Moreover, thanks to the intuitive and instructive style of my advisers and
collaborators I was able to learn a great deal of ecology, physiology, and
evolution in a short time. Through frequent discussions and intense
directed reading I was able to gain much of the knowledge and intuition
that has helped me in my research and led my investigations to their
What do you consider the main focus of your
research, and what drew your interest to this particular
I want to identify which factors constrain, organize, and control diversity
in ecological systems because I feel this will reveal the fundamental
features that shape the ecological and evolutionary patterns we observe in
nature. I try to answer these types of questions by studying how
"intrinsic" organismal physiology influences ecological and evolutionary
processes and how this influence is affected by and helps to mediate
"extrinsic" environmental factors.
Metabolic rate sets the pace of life and helps determine development times,
birth rates, mortality rates, and generation times. These life history
attributes in turn govern rates of population growth and carrying
capacities, and those in turn affect biodiversity, community composition,
and speciation-extinction rates.
Putting flesh onto this skeleton of connections has been the focus of much
of my work. I do this by making the mechanisms more explicit, quantitative,
predictable, and thus testable. This is achieved by developing novel
theories based on first principles and by testing predictions with
extensive empirical data.
Much of my current work and future directions depend on tying the
environment to this causal chain from the organism to the ecosystem. Global
warming and climate change have the potential to dramatically impact
biological systems and potentially to reduce the amount of diversity in
species and traits. Since metabolic rate depends strongly on body
temperature, changes in environmental temperature will directly alter the
metabolic rate of cold-blooded organisms, and this change will cascade
through the causal chain, affecting processes at every level.
Fortunately, there is a simple mathematical function that describes how
metabolic rate depends on body temperature, and this function can be
inserted and followed through the causal chain from the organism to the
ecosystem to help predict how biodiversity, community composition,
predator-prey interactions, and rates of evolution may be affected by
I am also trying to understand more complicated feedbacks, such as
correlations among the environment, the organism, and the ecosystem. For
example, temperature, light, and precipitation are crucial environmental
factors and are often correlated in space and time. These correlations
affect relationships among plant traits (e.g., optimal temperature for
growth, total leaf area, and water uptake rate), the ability of plants to
respond to environmental change, and thus biodiversity levels and community
composition in ecosystems.
One of your most-cited papers in our database is
the 2004 Ecology review article, "Toward a metabolic theory
of ecology," (Brown JH, et al., 85: 1771-89, July 2004).
Would you describe the ideas behind using metabolism to study
The fundamental idea is that an individual’s metabolic rate
dramatically influences both how it interacts with other individuals and
how it responds to the environment. In the first case, metabolic rate sets
an organism’s pace of life by speeding up or slowing down its growth
rate, mortality rate, feeding rate, and interaction rate with other
individuals and species. In the latter case, environmental temperature,
food availability, oxygen concentration, and other environmental factors
speed up or slow down metabolic rate and thus the organism’s pace of
life and how it interacts with other organisms.
By serving this dual role and linking the environment to the individual and
to interactions with other organisms, metabolic rate underlies large swaths
of ecology. After all, the field of ecology is defined as the study of how
organisms interact with each other and their environment.
Recent advances in theory and data analyses have helped to reveal how and
why an individual’s metabolic rate depends on body mass and body
temperature in specific, quantitative ways that apply across diverse taxa
such as unicellular organisms, insects, plants, amphibians, fish, reptiles,
birds, and mammals. These advances may enable the construction of a single
mathematical framework that uses metabolic rate to link the environment,
the individual, and interaction rates. These advances are still ongoing by
myself as well as West, Brown, Brian Enquist, Jamie Gillooly, Drew Allen,
and many others.
How was the metabolic theory idea accepted by the
The community’s response to this work has been very mixed, ranging
from the embrace of it as a "Newton’s laws" for ecology to the
declaration that it is fatally flawed. Virtually all new ideas in science
are met with debate and critique. These debates are vital because they lead
to deeper explanations of the original work, better methods for
communicating ideas, new perspectives on how the work relates to other
problems, and the identification of incorrect assumptions. Valuable
criticisms of metabolic theory are currently being absorbed by the
community and are already resulting in the theory being taken in new and
In some cases, criticisms have resulted from miscommunications that I
believe are partly due to systematic problems in the communication of
science. In particular, there is no common language for interdisciplinary
work that draws on ecology, physiology, mathematics, and physics. This lack
of language is exacerbated by the brevity of journal articles and by a lack
of knowledge on the part of all researchers, who cannot possibly have a
mastery of all fields.
I think these problems can be partially solved through more detailed
supplementary materials, an ever-evolving and improving language for
interdisciplinary studies, and increased consultation and collaboration
among researchers from different fields. I am also encouraged by the trend
in which younger scientists are being trained in a more interdisciplinary
manner. At this point, I am optimistic that metabolic theory will continue
to be developed and revised into an ever more useful framework that
provides a parsimonious explanation for large amounts of empirical data.
Where do you see this research going in five to
Much of the work thus far has focused on the effects of body size and body
temperature on metabolic rate and thus how these factors influence
biological and ecological processes. I think future work will identify
other factors that play an important role in determining metabolic rate,
such as ecological stoichiometry and nutrient or water availability. I also
think the understanding of species interactions will improve by having more
detailed spatial models and by incorporating effects of behavior (e.g.,
predator or prey strategies), diet, and sensory detection.
Finally, I think better theory will be developed to predict how fluctuating
environments will be mediated by metabolic responses and how that will
impact ecological systems. I envision such theories as being based upon
traits that characterize different functional groups and how their growth
is tied to the environment. Such theories will also necessarily be
integrated with effects of the environment on adaptation and speciation,
and hence, with the complicated feedbacks between environments, organisms,
What should the "take-away lesson" about your work
be for the general public?
Metabolic rate is the power that organisms use for maintenance, growth, and
reproduction and is uniquely capable of linking the environment to an
organism’s pace of life in terms of births, deaths, and interactions
with other individuals, such as eating or sex. Recent advances enable more
exact descriptions of these links in a manner that is roughly the same for
bacteria, plants, and animals. This work may be useful for providing a
unifying framework to ecology and for understanding how global warming,
resource availability, and other environmental fluctuations will impact
biological and ecological systems.
Van M. Savage, Ph.D.
Department of Systems Biology
Harvard Medical School
Boston, MA, USA
Van Savage's most-cited paper with
224 cites to date: