『Abstract
Tropical mountain areas may undergo rapid land degradation as
demographic growth and intensified agriculture cause more people
to migrate to fragile ecosystems. To assess the extent of the
resulting damage, an erosion rate benchmark against which changes
in erosion can be evaluated is required. Benchmarks reflecting
natural erosion rates are usually not provided by conventional
sediment fluxes, which are often biased due to modern land use
change, and also miss large, episodic events within the measuring
period. To overcome this, we combined three independent assessment
tools in the southern Ecuadorian Andes, an area that is severely
affected by soil erosion. first, denudation rates from cosmogenic
nuclides in river sediment average over time periods of 1-100
k.y. and establish a natural benchmark of only 150± 100 t km-2
yr-1. second, we find that land use practices have
increased modern sediment yields as derived from reservoir sedimentation
rates, which average over periods of 10-100 yr to as much as 15×103
t km-2 yr-1. Third, our land cover analysis
has shown us that vegetation cover exerts first-order control
over present-day erosion rates at the catchment scale. Areas with
high vegetation density erode at rates that are characteristically
similar to those of the natural benchmark, regardless of whether
the type of vegetation is native or anthropogenic. Therefore,
our data suggest that even in steep mountain environments sediment
fluxes can slow to near their natural benchmark levels with suitable
revegetation programs. A set of techniques is now in place to
evaluate the effectiveness of erosion mitigation strategies.
Keywords: erosion; vegetation cover; human impact; land use change;
cosmogenic nuclides; Andes』
Introduction
Methods
Natural and modern erosion rates
Vegetation control on erosion rates
Conclusions
Acknowledgments
References cited