Restoring dense vegetation can slow mountain erosion to near natural benchmark levels
Veerle Vanacker - Department of Geography and Geology, Université Catholique de Louvain,
Belgium; Institute for Mineralogy, University of Hannover, Germany
Friedhelm von Blanckenburg - Institute for Mineralogy, University of Hannover, Germany
Gerard Govers - Physical and Regional Geography, Katholieke Universiteit Leuven, Belgium
Armando Molina - Physical and Regional Geography, Katholieke Universiteit Leuven, Belgium
Jean Poesen - Physical and Regional Geography, Katholieke Universiteit Leuven, Belgium
Jozef Deckers - Division of Soil and Water Management, Katholieke Universiteit Leuven, Belgium
Peter Kubik - Paul Scherrer Institute, Institute of Particle Physics, Zurich, Switzerland
2007 Geological Society of America.
Geology, April 2007; v. 35; no. 4; p. 303–306
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, three independent assessment tools were combined 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, it was found that 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, the land cover analysis has
shown 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, the data suggests 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.