Elsevier

Environmental Science & Policy

Volume 80, February 2018, Pages 95-104
Environmental Science & Policy

Assessing the role of artificially drained agricultural land for climate change mitigation in Ireland

https://doi.org/10.1016/j.envsci.2017.11.004Get rights and content
Under a Creative Commons license
open access

Highlights

  • IPCC Wetlands Supplement strongly increased default EF of drained organic soils.

  • This makes their rewetting more attractive as a climate change mitigation measure.

  • Drainage emissions and mitigation potential were analysed for Irish agriculture.

  • We calculated annual emissions from histic and humic soils as 8.7 and 1.8 Tg CO2e.

  • Rewetting 50% of histic soils could generate annual GHG savings of 3.2 Tg CO2e.

Abstract

In 2014 temperate zone emission factor revisions were published in the IPCC Wetlands Supplement. Default values for direct CO2 emissions of artificially drained organic soils were increased by a factor of 1.6 for cropland sites and by factors ranging from 14 to 24 for grassland sites. This highlights the role of drained organic soils as emission hotspots and makes their rewetting more attractive as climate change mitigation measures. Drainage emissions of humic soils are lower on a per hectare basis and not covered by IPCC default values. However, drainage of great areas can turn them into nationally relevant emission sources. National policy making that recognizes the importance of preserving organic and humic soils’ carbon stock requires data that is not readily available. Taking Ireland as a case study, this article demonstrates how a dataset of policy relevant information can be generated. Total area of histic and humic soils drained for agriculture, resulting greenhouse gas emissions and climate change mitigation potential were assessed. For emissions from histic soils, calculations were based on IPCC emission factors, for humic soils, a modified version of the ECOSSE model was used. Results indicated 370,000 ha of histic and 426,000 ha of humic soils under drained agricultural land use in Ireland (8% and 9% of total farmed area). Calculated annual drainage emissions were 8.7 Tg CO2e from histic and 1.8 Tg CO2e from humic soils (equal to 56% of Ireland’s agricultural emissions in 2014, excluding emissions from land use). If half the area of drained histic soils was rewetted, annual saving would amount to 3.2 Tg CO2e. If on half of the deep drained, nutrient rich grasslands drainage spacing was decreased to control the average water table at −25 cm or higher, annual savings would amount to 0.4 Tg CO2e.

Keywords

LULUCF
Greenhouse gas
Histosol
Peatland
Organic soil
IWMS

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