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change on soil erosion. It should be noted that the
most complete studies were applied using contin-
uous models at the slope scale, possibly due to the
availability of data to evaluate these models; stud-
ies at the watershed scale and using extreme event
models are rarer and appear, in comparison, to be
less developed. Despite the higher number of slope
applications, current modelling approaches are
still limited in space and scope, and therefore it is
difficult to extrapolate the results to more general
conclusions. It can perhaps be said that this branch
of climate change impact science is not yet fully
developed, and that modelling approaches still
need further testing, refinement and discussion
before robust results can be presented.
However, one overall conclusion indicated by
the results of the different studies is that the rela-
tionship between soil erosion and climate change
is complex and depends upon a number of impacts
highlighted at the start of this chapter. Further-
more, soil erosion processes are themselves
highly sensitive to changes in driving forces,
making it difficult to exclude complexity from
the analysis without invalidating the main con-
clusions. These issues should be taken into
account when designing a modelling approach to
be applied in a particular case study. Two broad
conclusions emerging from this work relate the
patterns of changes in climate with erosion
response, at least at the slope scale:
●
where rainfall is expected to increase signifi-
cantly, this dominates erosion response; and
●
where rainfall is not expected to change or is
expected to decrease, more complex processes
take hold, with the dominant processes involving
a relationship between changes to rainfall and
vegetation biomass.
The results are not sufficient for a quantitative
estimate of these impacts, and there are still
many knowledge gaps surrounding these esti-
mates, especially when transferring results from
slope-scale studies to larger scales. Some of these
gaps are related to more general issues in soil ero-
sion science, such as the lack of data and the
uncertainties surrounding estimates in erosion
magnitude, location of hotspots, on- and off-site
impacts and conservation measures (Boardman,
2006). The knowledge gaps on the impacts of cli-
mate change on soil erosion can be, in broad
terms, systematized in a few questions:
●
Can we upscale model results at the individual
hillslope and watershed scales to regional and
global scales?
●
What is the uncertainty surrounding the
estimates?
●
Which are the links and feedbacks between soil
erosion and land use/land cover that can be
affected by climate change, and which adaptation
measures can be taken?
15.5.1
Upscaling results to the regional
and global scales
Most of the studies presented earlier in the chap-
ter focus on single hillslopes or, at most, water-
sheds. While these applications have been
extremely useful to increase our understanding of
the processes behind the impacts of climate
change, one can question whether the results can
be upscaled. Soil erosion is a phenomenon with
high variability in space and time, and different
processes intervening at different scales. The
PESERA study (Mantel
et al
., 2003) highlighted
the high spatial variability of climate change
impacts on soil erosion, even at the hillslope scale;
the within-watershed results by Nunes (2007)
showed how impacts may vary with spatial scale.
Both studies have been hampered by the lack of
data to evaluate the modelling approach used.
These issues, especially the lack of erosion
data, appear to limit the feasibility of grid-based
impact assessment studies at the regional or glo-
bal scale, such as those currently done for surface
runoff (e.g. Nohara
et al
., 2006). The lack of
regional or global-scale erosion estimates for cur-
rent conditions (Boardman, 2006) should be over-
come before attempting to upscale climate change
impacts. Furthermore, the studies presented in
this chapter are not evenly distributed through-
out the globe. Most studies have focused on the
mid-latitudes, with temperate humid and semi-
arid climates; subtropical regions and the high
latitudes are poorly represented by comparison,
which could limit the understanding of particular
