Late last year, the work of Dr. G. Arturo
Sanchez-Azofeifa entered the top 1% in the field of
Environment & Ecology in Essential Science
Reuters. His current record in the overall database
includes 38 papers cited 633 times between January 1,
1998 and December 31, 2008.
Dr. Sanchez-Azofeifa is Director of the Center for
Earth Observation Sciences (CEOS), a Professor at the
Earth and Atmospheric Sciences Department, and a
Principal Investigator of the TROPI-DRY Collaborative
Research Network funded by the Inter American Institute
for Global Change Research (IAI) at the University of
In the interview below,
ScienceWatch.com correspondent Gary Taubes talks with Dr.
Sanchez-Azofeifa about his highly cited work.
As a civil engineer by training, how did you get
involved in deforestation and climate change research?
In the early 1990s, I came to the US on a Fulbright scholarship to do a
masters and Ph.D. in hydrology at the University of New Hampshire. At the
time, I had the opportunity to work with a very good group at the
university that was working on deforestation in the Amazon basin, using
remote sensing. While working on my dissertation, I met such people as Paul
Ehrlich, Kamal Bawa, and Robert Harris, and they are the ones who actually
pulled me into this line of work over the years, and we’ve continued
working together in this area. A lot of my work has been derived from
interactions and discussions with them.
What was your first approach to studying
Looking at the effects of parks on deforestation. Basically Kamal and I
asked ourselves in 1998 whether national parks were effective or not in
preventing deforestation, and I think we published probably one of the
first papers in Conservation Biology about those issues. We looked at a
very important park in Costa Rica and we used remote sensing to look at how
deforestation and fragmentation were occurring in the vicinity of the park.
Could you explain what fragmentation is?
Taking a huge portion of forest and cutting it into little pieces. When you
look at the Amazon now, you see what you often see in the American Midwest,
small patches of forest in the middle of vast fields. That’s what we
call fragmentation. My work in Costa Rica over the years has been along
those lines, and we did the first inventory of deforestation and
fragmentation in the region and we’ve continued working on this,
publishing a lot of papers that have had impacts on policy, environmental
services, water resources, etc.
One of your most-cited papers in our database is the
2006 Nature article, "Widespread amphibian extinctions from
epidemic disease driven by global warming." Would you walk our readers
through this paper and its findings?
The paper was motivated by the work of Alan Pounds, the first author. There
was a lot of discussion at the time about whether climate change was
affecting cloud forests, which are forests at the top of mountains; not
alpine forests, but forests affected by the constant movement of clouds.
The best way to understand this is to look at the Monteverde cloud forests,
which is where Pound works. We met through the Tropical Science Center in
Costa Rica. There were some theories floating around for years talking
about the effect of deforestation on local climates and that this could
explain the disappearances of frogs, for instance. I remember talking to
Alan about this and we were thinking that there must be something else
My work in the team was to provide all the deforestation analysis based on
satellite analysis that went into the model, which ultimately demonstrated
that deforestation was, in fact, not a factor in the disappearance of frogs
in Monteverde. That led, in turn, to the whole theory of climate change and
how changes in micro-temperature during the day and night affected the
disappearance of frogs. We had evidence from other sites, as well, so that
story became more significant.
Why do you think that paper has been so highly
I think there are two reasons. One is the time it was
released—January 12th 2006. I remember being at my house
when Nature released that paper. It seemed like two minutes later
when the phone started ringing, and it kept ringing for hours. This story
was all over the place—it was in 278 newspapers in a week. It turns
out this was when the Intergovernmental Panel on Climate Change (IPCC) was
preparing to release its 2007 report, its fourth assessment on climate
change, and the IPCC report actually cited our paper as demonstrating one
of the effects of climate change. In practice it was very unique. We
actually demonstrated that the frogs had been killed by pathogens, but what
was happening was that the pathogen was moving into higher elevations
because of the temperature change. Some people say that climate change is
the trigger for the bullet that is killing the frog. So I think that opened
When someone writes a paper on this subject, the first thing their
introduction has to do is frame the work inside a body of knowledge, and
ours is a very important paper in this respect. When people want to say
that climate change has an impact on biodiversity, then Pounds et
al. is the first paper they cite. When the disbelievers write their
papers, they use Pounds et al. to define their own theories. And
once we had a couple of replies in Nature and another reply in
another journal, the whole thing snowballed. The key element—and
it’s important to stress this—is that the paper was used by the
IPCC as among the first evidence of the effect of climate change in Latin
America, a topic on which we have very little information.
What do you consider the most challenging aspect of
studying the effect of climate change on deforestation?
I think it is always difficult to work with remote sensing on a site
that’s always covered with clouds. Those are optical satellites,
after all. If you have clouds, you cannot see the forest and so you have
trouble developing algorithms that the modeling team can use to get
accurate rates of deforestation. That, to me, is now the most challenging,
although over the years it’s not actually the most difficult thing
we’ve ever done.
OK, so what was the most difficult?
Ever? Oh, man. There’s a paper by Phillips from the Royal Academy of
Science in England, published in one of the top journals, in which he talks
about the 10 fingerprints of global change in the tropics—hunting,
fragmentation, things like that (Lewis SL, et al., "Fingerprinting
the impacts of global change on tropical forests," Phil Trans. Roy.
Soc. London B-Biol. Sci. 359: 437-62, 29 March 2004). And one he
mentions is the increase in the extent of lianas—these woody vines
that climb around and between trees. Lianas are parasites that extend all
the way to the top of the tree. The question is, if lianas are so important
for global change, which Phillips and others have documented, and if the
extent of lianas is increasing in the tropics and is strongly related to
the increase in CO2, could we detect the lianas from space using satellite
So I developed a program of research with postdocs, students, etc., trying
to answer that question. I went from the question of how the leaves of the
lianas reflect light compared to the leaf of a tree. I tried to extrapolate
from there to the canopy and from there to the landscape. I used
construction cranes in Panama, in the middle of forests, to understand
those processes. To me, this is the most difficult thing I’ve ever
done. And one thing I can say so far is that we cannot detect the extent of
lianas in tropical rain forests from satellites, but we can do it in
tropical dry forests.
You caught me right now addressing the reviews of that paper. One referee
said we quote ourselves too much and we have to explain to the editor that
we have to do that because nobody else is doing this work. It seems to me
that for a long time researchers working on forests did not make the
connection that lianas are important or that they are even part of a
tropical ecosystem. It is like they do not exist. The only thing
researchers saw was the tree. In some cases, lianas may constitute 70% of
the structure of the forest. There is a tree in Panama, for example, with
27 species of lianas in one single crown. Sometimes the lianas become so
heavy that they kill the tree.
It seems like you’ve become fascinated with lianas
in and of themselves.
"I think it is always difficult to
work with remote sensing on a site
that’s always covered with
I have. Lianas just grow. They don’t have to put any energy into
generating trunks and branches. The energy all goes to leaves and growing.
It’s really interesting, and I think this is opening up a whole new
line of research. People are now starting to write proposals on this.
People have worked on the ecology of lianas for many years but not this
linkage between the ecology of lianas on a tree and the observation of the
presence of the life form in a crown of a tree using satellites. So, yes,
this to me is one of the most difficult things to do and we’re still
struggling with that.
Another of your highly cited papers is the 2001
Ecological Applications paper, "Countryside biogeography: Use
of human-dominated habitats by the avifauna of southern Costa Rica,"
(11: 1-13, February 2001). Would you please talk a little about
this paper and its significance for the field?
This paper is with Gretchen Baily and Paul Ehrlich and it was published in
Ecological Applications in part because we introduced this concept
of countryside biogeography. That’s the seminal paper in which we
presented the concept and demonstrated the principle of it, and people can
then use it to help develop this field of study. And that’s why this
paper is so highly cited.
So what exactly do you mean by the term "countryside
The understanding of effects of fragmentation in the landscape, considering
the matrix of the landscape. For many years, fragmentation and the effects
of fragmentation on biodiversity considered just forest and non-forest,
which is effectively everything that’s not a tree. In this paper with
Gretchen and Paul, we moved away from that concept and looked beyond forest
We were looking at what the landscape looks like; what happens when you
have coffee plantations? What about if it’s sugar cane? What if it is
half sugar cane, half coffee? What if you have a forest that is surrounded
by a coffee plantation, and the coffee plantation has trees that can be
used by birds as a stepping stone? That is the kind of research that this
paper opened and I think that’s why it’s so highly cited.
Where do you see your research going in five to ten
I think that it will go in several main lines. We are going to continue
working on the issue of lianas: how can we map their presence and absence
in tropical dry forests? That’s where we're finding more significant
differences between the lianas themselves and their host trees. The second
will be dealing with the role of climate change phenology; that is, the
change of seasons, from winter to spring to summer to fall in dry forest
environments. We have ways to quantify that transition dynamic using
satellites. We have long-term remote-sensing time series and it's
interesting to see how those processes have been captured over the last 30
years, and if there are any trends, and where those trends are more
The third one is an area that has not been explored in depth by anyone,
which is the role of endophytes in the response to climate change.
Endophytes are fungi that live inside the leaf. They’re important
when you consider the theory of how a leaf reflects light and then
extrapolate this to the canopy and then to the landscape. Most satellites
have sensors that look in the near-infrared, and the way that a leaf
reflects light is in the near-infrared. When you take a cross-section of a
leaf and look at it with a microscope, you’ll find that in the middle
of the leaf there’s the spongy mesophyll. It actually looks like a
sponge. Light goes through the epidermis of the leaf and reflects inside
the spongy spaces of this spongy mesophyll. The theory says that the way a
leaf reflects light in the near infrared is related to the amount of empty
space inside the leaf. Now guess where the endophytes go—inside those
What we want to know is the relative contribution of those fungi to light
reflectance and how they use that light. And we are finding some phenomenal
things. For example, in one single leaf you can find up to 10 or even 16
different species of endophytes. One plant may have over 120 species of
endophytes. And nobody has ever looked at this. So we’re starting to
develop a line of research to understand the role of endophytes on the
spectral reflection of light from leaves.
Department of Earth and Atmospheric Sciences
University of Alberta
Edmonton, Alberta, Canada