The surface of the Earth is rapidly changing, largely in response to anthropogenic perturbation. We now realize that almost half of the land surface on Earth has been transformed by human activity, including vast and sometimes devastating transformations of soils. With the human population doubling to about 10 million people in 50 yr, there is a growing concern about soil resilience and sustainable development.
We are focusing on the following two research questions:
1. What are the impact and feedback mechanisms of human activities on land degradation?
Land use modification and conversion by human activities have large impacts on ecosystem functions, such as biogeochemical cycles, biological diversity and natural hazards and risks. Human-induced land use has accelerated soil erosion and increased sediment transport by large rivers. Various field studies have documented that mean rates of soil loss on agricultural plots may exceed the rates of soil formation by as much as an order of magnitude. Tropical mountain areas in particular are undergoing rapid soil erosion, which is currently limiting their agricultural growth potential. Notwithstanding the growing number of field studies on the effect of land use change on erosion rates, quantitative information on the importance of humans as agents of mountain erosion is scarce. Modern elevated sediment fluxes in tropical mountain areas are commonly attributed to improper land management, although natural process rates may be high due to steep slopes, tectonic activity, and the erosive climate.
We aim to better understand the role of human activities
on the sediment cycle in mountainous regions. Using new geochemical methods such as in-situ produced cosmogenic nuclides
, we are able to quantify natural erosion benchmarks. These measures allow us to quantify the impact of human activities on sediment fluxes
. Furthermore, we are highly interested in the link between land use and degradation. For various pathways of land use change, we are working on specific hypotheses that allow us to better understand the causes and consequences of degradation
in anthropogenic landscapes.
2. Can we predict geological denudation rates from landscape morphology?
Topographic variables are often used as surrogates for inferring landscape processes. Landscape evolution models commonly predict erosion rates based on a simple linear functional relation between erosion rates and hillslope morphology. This classic assumption that the rate of erosional processes depends on terrain steepness, measured as mean local relief or mean slope gradient, has recently been challenged for steep terrain.
Relief evolution in threshold landscapes is strongly dependent on the fluvial network that sets the local base level for hillslope processes.
In contrast to the slopes, the fluvial network is directly coupled to the basin outlet, and keeps consistently track of any change in tectonic or climatic forcing by changing its bed morphology, channel width and gradient. At the moment, the extent to which basin-wide denudation rates can directly be inferred from slope and channel morphology is still difficult to evaluate. More quantitative data on basin-wide denudation rates for tectonically active topographic ranges are necessary to establish such relationships.
We are focusing on two regions that are representative for two completely different tectonic domains: the Ardennes-Rhenish Massif
(Belgium), and the Northern Andes (Ecuador). We specifically analyse spatial patterns in erosion and river incision rates in relation to regional tectonic differentiation patterns.
