Double trouble: subsidence and CO2 respiration due to 1,000 years of Dutch coastal peatlands cultivation

Abstract

Coastal plains are amongst the most densely populated areas in the world. Many coastal peatlands are drained to create arable land. This is not without consequences; physical compaction of peat and its degradation by oxidation lead to subsidence, and oxidation also leads to emissions of carbon dioxide (CO 2 ). This study complements existing studies by quantifying total land subsidence and associated CO 2 respiration over the past millennium in the Dutch coastal peatlands, to gain insight into the consequences of cultivating coastal peatlands over longer timescales. Results show that the peat volume loss was 19.8 km 3 , which lowered the Dutch coastal plain by 1.9 m on average, bringing most of it below sea level. At least 66 % of the volume reduction is the result of drainage, and 34 % was caused by the excavation and subsequent combustion of peat. The associated CO 2 respiration is equivalent to a global atmospheric CO 2 concentration increase of~0.39 ppmv. Cultivation of coastal peatlands can turn a carbon sink into a carbon source. If the path taken by the Dutch would be followed worldwide, there will be double trouble: globally significant carbon emissions and increased flood risk in a globally important human habitat. The effects would be larger than the historic ones because most of the cumulative Dutch subsidence and peat loss was accomplished with much less efficient techniques than those available now.

Advances and Practices on the Research, Prevention and Control of Land Subsidence in Coastal Cities

“…2000 years ago (Pierik et al, 2018), but was intensified and consistently expanded approximately 1000 years ago under conditions of rapid population growth. Land was reclaimed for agriculture and peat was excavated for fuel (Borger, 1992;Van Dam, 2001;Erkens et al, 2016). Due to continued drainage of this area inducing compression of peat and clay layers and oxidation of organic material above phreatic groundwater level, land subsidence is still going on with typical regional rates of 1-12 mm/yr (Koster, 2017).…”

“…As a result, subsidence accelerates, which forces lowering of the groundwater level, making subsidence a self-perpetuating process (cf. Erkens et al, 2016). Calculations were based on two existing models: peat oxidation based on empirical relations between average lowest groundwater levels and oxidation in The Netherlands and compaction based on Koppejan (Terzaghi -based).…”

Peat layer accumulation and post‐burial deformation during the mid‐late Holocene in the Po coastal plain (Northern Italy)

“…Organic matter content, plant species composition, water table position and thickness of the overlying sediment column appear to be the main factors controlling the amount of peat compaction (van Asselen, Stouthamer, & Smith, ). High compressibility of peat layers has been often called into question as one of the main drivers of delta plains subsidence and evolution (van Asselen, ; van Asselen et al, ; Drexler, Fontaine, & Deverel, ; Erkens, Meulen, & Middelkoop, ; Törnqvist et al, ).…”

A new soil mechanics approach to quantify and predict land subsidence by peat compression

“…Especially, overexploitation of aquifers and artificial lowering of groundwater levels for agricultural practices has caused volume reduction of subsurface layers due to increased effective stress, resulting in subsequent land subsidence [Galloway and Burbey, 2011]. Recently, the volume reduction of peat due to overburden and groundwater level lowering has been identified as one of the main contributing components, causing land subsidence in the Mississippi delta [Törnqvist et al, 2008], the Rhine delta [Erkens et al, 2016], Sacramento-San Joaquin delta [Drexler et al, 2009], and inland Kalimantan [Kool et al, 2006].…”