operational definition of "global change" encompasses
far more than just changes in climate and atmospheric composition.
It also includes change in land use, as driven by demographic,
economic, technological, and social pressures. Over the next
few decades this human dimension of global change will have
the most profound influence on the fate of terrestrial ecosystems;
one aspect intimately associated with this change in land
use (but also linked to the other changes discussed above)
is soil erosion and it poses a major threat for sustainable
erosion is a very widespread phenomenon, and is usually irreversible.
Once the nutrient-rich surface soil has been lost, the ability
to sustain plant growth is severely reduced, and increased
runoff from the more impermeable subsoils results in reduced
plant-available water. Furthermore, erosion brings various
associated "off-site" problems, including reduced
water quality from increased sediment loads and poorer air
quality due to dust.
has long been known that both water and wind erosion are commonly
accelerated by degrading vegetation cover, presently the main
manifestation of global change; given a relatively stable
set of conditions many successful strategies have been developed
for combating erosion. Global change will, however, bring
added problems, as it encompasses more than just change in
land-use; change in atmospheric composition and, more particularly,
change in climate will further stress many systems. The severity,
frequency and extent of erosion will certainly be altered
by changes in rainfall amount and intensity, and by changes
in wind. Global change will thus amplify many current problems,
but as certain soil thresholds are exceeded, potentially new
and different problems could arise. It will therefore be crucial
to understand the potential impacts of global change on soils
to allow the predictive capability necessary to improve their
management in the future to be developed. The "GCTE Soil
Erosion Network" (one of the key components of the soils
research agenda of the Global Change and Terrestrial Ecosystems
Core Project of the International Geosphere-Biosphere Programme),
is dedicated to this goal.
of the unique features of GCTE is that it has set an internationally
agreed research agenda (the GCTE Operational Plan, see above)
to investigate the interactive effects of changes in the global
change drivers. To achieve its aims, this research will require
collaboration between research teams, between nations and
between disciplines. The GCTE Soil Erosion Network is designed
to provide the international coordination and linkages necessary
to achieve the Network's objectives.
To design and undertake experimental and monitoring programmes
to provide a predictive understanding of the impacts of
changes in climate and land-use on soil erosion.
To refine and adapt current erosion models for use in global
change studies from plot to regional scales.
GCTE Soil Erosion Network is being developed around three
closely interrelated themes:
erosion processes commonly only start beyond a certain threshold
set of conditions, emphasis will be put on the determination
of such thresholds, on reversibility of processes, and on
soil resilience. Infrequent climatic events, such as heavy
storms, typhoons, etc. can trigger severe erosion, that
would be unpredictable from short-term records. Long-term
erosion monitoring is therefore essential to observe possible
transient and non-equilibrium responses to climatic and
land use changes. For inclusion in the Network monitoring
the numerous current and past soil erosion experiments,
many uncertainties about the mechanisms involved remain.
Furthermore, as many experiments are very site-specific,
extrapolation of results is difficult. These uncertainties
must be resolved by detailed experimentation to gain the
understanding required to allow models to be developed that
are both highly sensitive to global change and sufficiently
flexible to be relevant under the largest range of conditions.
experiments have often been at the "run-off" plot
scale, using land cover and tillage as experimental variables.
These variables are of course key determinants of erosion
rate, and the Network will build on the valuable base-line
data and understanding gained from such experiments. However,
GCTE is interested in the interaction of global change driving
forces. The Network will therefore also examine the impact
of changed variance and mean for key climate parameters
and the effects of elevated CO2, via their direct
and indirect impact on aggregation and aggregate stability.
processes are both varied and complex, and several modelling
approaches have been developed for a range of temporal and
spatial scales, for erosion by both water and by wind. These,
and other, approaches need to be systematically validated
across environmental space to determine which are most robust
for global change studies. The broad range of data covering
the space-time domain flowing from the many monitoring and
experimental programmes worldwide will be used to calibrate,
initialize and validate soil erosion simulation models;
this will be one of the primary objectives of the network.
three aspects of the Network are discussed in detail in a
series of papers related to the GCTE Soil Erosion Network
published in a special issue of the Journal of Soil and
Water Conservation, 51, 1996.)
about how to join the GCTE Erosion Network are given in Annex
and Structure of this Report
Report lists the metadata (descriptions) of those projects
that are formally accepted in the GCTE Soil Erosion Network
at the time of printing (further studies are very much welcomed
- see Annex III). Its aim is to promote collaboration by publicising
and detailing work suitable for global change studies; it
allows researchers to identify suitable work for bi- and multi-lateral
Report is structured in four sections: Models; Experiments;
Monitoring Studies; and Annexes. Models appear in alphabetical
order according to model name, and experiments and monitoring
studies according to contact name.
further details about the GCTE Erosion Network, please contact:
Valentin, GCTE Task 3.3.2 Leader
ORSTOM, 32 Rue Henry Varagnat, 93143 Bondy Cedex, FRANCE.
Tel +33 1 48025500
Fax +33 1 48473088
Ingram, GCTE Focus 3 Officer
GCTE Focus 3 Office, NERC Centre for Ecology and Hydrology
Maclean Building, Crowmarsh Gifford, Wallingford, Oxon OX10
Tel +44 1491 692410
Fax +44 1491 692313