The human impact on North American erosion, sediment transfer, and storage in a geologic context

Abstract

Humans are primary agents of geomorphic change, and rates of anthropogenic landscape change likely far exceed the pace of change expected from natural geologic processes. Nevertheless, our understanding of the impact of humans on the natural landscape is limited by difficulties in accurately comparing past and present rates of change across wide spatial and temporal scales. Here, we present a compilation of >4000 rates of alluvial sediment accumulation that provide an indirect record of North American erosion, mass transfer and sediment storage from the late Pleistocene to the present day. Continent-wide rates of alluvium accumulation were broadly stable for ~40,000 years, but increased 10-fold during the rapid expansion of agriculture and river system modification associated with European colonization. Interpreted in terms of mass transfer, humans have moved as much sediment in North America in the past century as natural processes can transfer in 700–3000 years.

Comment on esurf-2021-7

“…and may have different impacts on erosion, our results strongly point to the overwhelming impact of agriculture and related activities on short-term erosion rates, corroborating previous work (Dedkov and Mozzherin, 1996;Montgomery, 2007;Wilkinson and McElroy, 2007;Kemp et al, 2020). However, it is worth noting that the difference in short-term erosion rates between anthropogenic and non-anthropogenic regions shown here is smaller than was shown in previous studies (Dedkov and Mozzherin, 1996;Montgomery, 2007;Wilkinson and McElroy, 2007;Kemp et al, 2020). For example, Dedkov and Mozzherin (1996) estimated that anthropogenic activities increase sediment yields by a factor of 3.5 in large rivers and 8 in small rivers.…”

“…Previous studies have shown that, in some regions, short-term erosion rates are higher than long-term rates because of recent human activities (Clapp et al, 2000;Gellis et al, 2004;von Blanckenburg, 2006;Kemp et al, 2020) or climatic change https://doi.org/10.5194/esurf-2021-7 Preprint. Discussion started: 24 February 2021 c Author(s) 2021.…”

“…Human activities have increased short-term erosion rates by an estimated one to two orders of magnitude (Milliman and Syvitski, 1992;Dedkov and Mozzherin, 1996;Montgomery, 2007;Wilkinson and McElroy, 2007;Kemp et al, 2020), suggesting that human influences on sediment yields outweigh natural processes (Hooke, 2000;Wilkinson and McElroy, 2007;Kemp et al, 2020). Among the many human activities expressed on surface erosion around the globe, agriculture has one of the highest impacts on the land surface because it directly alters both vegetation through replacement of forest canopies with low-interception coverage crops, and soils through replacement of natural profiles containing developed organic layers with homogenised profiles that undergo cycles of tillage and surface compaction (Hooke, 2000).…”

“…Among the many human activities expressed on surface erosion around the globe, agriculture has one of the highest impacts on the land surface because it directly alters both vegetation through replacement of forest canopies with low-interception coverage crops, and soils through replacement of natural profiles containing developed organic layers with homogenised profiles that undergo cycles of tillage and surface compaction (Hooke, 2000). This anthropogenic disruption of vegetation and soils should create higher susceptibility to erosion by rainsplash, runoff, and wind (Dedkov and Mozzherin, 1996;Wilkinson and McElroy, 2007;Kemp et al, 2020). The eroded material would then contribute to stream channels, where it would be measured as elevated sediment flux compared to pre-historic levels.…”

“…In addition to climatic controls, land surface processes are strongly influenced by anthropogenic activities through construction, mining, timber harvesting, and conversion of natural vegetation to agriculture (crop and pasture), the last of which is the most dominant in terms of area (Hooke, 2000). Global analyses of short-term erosion rates from suspended sediment records suggest that a change to agricultural land cover has enhanced erosion rates by one to two orders of magnitude (Dedkov and Mozzherin, 1996;Montgomery, 2007;Wilkinson and McElroy, 2007;Kemp et al, 2020).…”