TY  - JOUR
A1  - Menges, Johanna
A1  - Hovius, Niels
A1  - Andermann, Christoff
A1  - Dietze, Michael
A1  - Swoboda, Charlie
A1  - Cook, Kristen L.
A1  - Adhikari, Basanta R.
A1  - Vieth-Hillebrand, Andrea
A1  - Bonnet, Stephane
A1  - Reimann, Tony
A1  - Koutsodendris, Andreas
A1  - Sachse, Dirk
T1  - Late holocene landscape collapse of a trans-himalayan dryland
BT  - human impact and aridification
JF  - Geophysical research letters
N2  - Soil degradation is a severe and growing threat to ecosystem services globally. Soil loss is often nonlinear, involving a rapid deterioration from a stable eco-geomorphic state once a tipping point is reached. Soil loss thresholds have been studied at plot scale, but for landscapes, quantitative constraints on the necessary and sufficient conditions for tipping points are rare. Here, we document a landscape-wide eco-geomorphic tipping point at the edge of the Tibetan Plateau and quantify its drivers and erosional consequences. We show that in the upper Kali Gandaki valley, Nepal, soil formation prevailed under wetter conditions during much of the Holocene. Our data suggest that after a period of human pressure and declining vegetation cover, a 20% reduction of relative humidity and precipitation below 200 mm/year halted soil formation after 1.6 ka and promoted widespread gullying and rapid soil loss, with irreversible consequences for ecosystem services.
KW  - geomorphology
KW  - paleoclimate
KW  - human activity
KW  - Tibetan plateau
KW  - late Holocene
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL084192
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 23
SP  - 13814
EP  - 13824
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Garcin, Yannick
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - de Saulieu, Geoffroy
A1  - Schefuss, Enno
A1  - Sebag, David
A1  - Dupont, Lydie M.
A1  - Oslisly, Richard
A1  - Brademann, Brian
A1  - Mbusnum, Kevin G.
A1  - Onana, Jean-Michel
A1  - Ako, Andrew A.
A1  - Epp, Laura Saskia
A1  - Tjallingii, Rik
A1  - Strecker, Manfred
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - Early anthropogenic impact on Western Central African rainforests 2,600 y ago
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest-savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the "rainforest crisis" to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. delta C-13-inferred vegetation changes confirm a prominent and abrupt appearance of C-4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. delta D values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era.
KW  - Western Central Africa
KW  - late Holocene
KW  - rainforest crisis
KW  - paleohydrology
KW  - human activity
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1715336115
SN  - 0027-8424
VL  - 115
IS  - 13
SP  - 3261
EP  - 3266
PB  - National Acad. of Sciences
CY  - Washington
ER  -