Sampurno Bruijnzeel talks
with ScienceWatch.com and answers a few questions
about this month's Emerging Research Front Paper in the
field of Engineering. The author has also sent along
images of their work.
Article: Hydrological functions of tropical
forests: not seeing the soil for the trees?
Journal: AGR ECOSYST ENVIRON, 104 (1): 185-228 SEP
Addresses: Free Univ Amsterdam, Fac Earth & Life Sci,
Boelelaan 1085-1087, NL-1081 HV Amsterdam,
Free Univ Amsterdam, Fac Earth & Life Sci, NL-1081 HV
To begin with, the paper received a flying start by being highly cited in
the widely read Polex Newsletter issued by the International
Centre for Forestry Research (CIFOR). This newsletter reaches an audience
representing many more disciplines than the journal in which the paper
itself was published at the time (Agriculture, Ecosystems and
In addition, there has been so much debate on the hydrological role of
(tropical) forest in recent years that many people have become confused and
simply do not know what to believe anymore. The issue is rather complex
indeed, in that the effect of deforestation or reforestration on streamflow
depends on the local setting in terms of rainfall, soils, and topography
and therefore one-liners are not good enough. I like to believe that the
paper has succeeded in striking the right balance in terms of complexity
and nuance, and this seems to appeal to many readers (from what I've
Does it describe a new discovery, methodology, or
synthesis of knowledge?
It is primarily a synthesis of knowledge on a topic (tropical forests and
water) that is both subject to heated debate and is also confusing to many.
How did you become involved in this research and were
any particular problems encountered along the way?
I went to Indonesia as a student in the mid-'70s to study forest hydrology
and gradually got more and more interested in the hydrological impacts of
land-cover change (deforestration, reforestration) in addition to the study
of the hydrological functioning of forest ecosystems themselves.
Written for a review such as Agriculture, Ecosystems &
Environment, my 2004 paper has also been helpful in identifying the
chief subjects requiring further research and the extent to which the
hydrology of degraded lands can be restored again. Examples include the
hydrology of tropical montane cloud forests, a rare type of evergreen
mountain forest found in tropical areas where local climatic conditions
cause cloud and mist to be regularly in contact with the forest vegetation.
These forests are receiving additional water inputs through cloud water
capture—a most elusive and difficult to quantify process.
Where do you see your research leading in the
Given the ongoing degradation of many areas in the humid and sub-humid
tropics and the surprising lack of good quantitative information on the
hydrological functioning of such degraded areas, I reckon there is an
urgent need to fill this lacuna.
In addition, with an increased emphasis lately on planting trees for the
mitigation of climate change, resulting in an increase in carbon
sequestration—usually without realizing the potentially adverse
effects on streamflow—efforts to quantify the hydrological
implications of all this tree planting need to be stepped up.
Finally, the hydrological implications of restoring badly degraded land
under a range of tropical climatic conditions constitute a major research
challenge for years to come.
Do you foresee any social or political implications for
Yes, for instance, the planned massive tree planting schemes (for carbon
sequestration, etc.) in sub-humid areas that do not support natural forest
(e.g., East Africa) are bound to backfire on the situation of water
Prof. Dr L.A. (Sampurno) Bruijnzeel
Chair of Land Use and Hydrology
Department of Hydrology and Geo-Environmental Sciences
Faculty of Earth and Life Sciences
VU University Amsterdam
Amsterdam, The Netherlands
Keywords: hydrological functions, tropical forests,
deforestation, reforestration, streamflow, rainfall, soils, topography,
hydrology of tropical montane cloud forests, hydrological functioning of
forest ecosystems, cloud water capture, tree planting schemes.