Description

·         A peatland is a type of wetland with a naturally accumulated layer of peat at the surface due to organic matter production exceeding decomposition[2]. Peatlands are generally classified as bogs and fens. Bogs are fed mainly by rain and snow, while fens develop in landscape depressions and are fed with surface and/or ground water. Other names referring to peatlands found in this review are swamp, and wet heath, though the search string included more synonyms (see section 4). Carbon-rich soils are included in this definition. These soils have and organic layer usually with >15 % of organic matter. However, the synthesis papers included in this review do not clearly define what they consider carbon-rich soils and thus we rely on authors’ knowledge and criteria to include individual studies in their reviews.

·         This review focuses on peatlands under agricultural use and thus, and though not clearly stated on the papers reviewed, includes mostly drained peatlands.

·         This review includes interventions towards an improved and more sustainable management of peatlands. Specific interventions have been proposed such as low tillage, ban of burning, paludiculture, etc[3]. In this literature review we have found evidence for the following management interventions:

o    No fertilisation. Fertilisers are natural or synthetic substances containing chemical elements such as nitrogen (N), phosphorus (P) and potassium (K) that are applied to soils to improve growth and productiveness of plants[4].  Fertilisation, and in particular N inputs in wetlands, might promote greenhouse gas emissions by changing element cycling[5]. Here, no fertilised peatlands are compared to fertilised ones.

o    Grazing is a method of animal husbandry in which livestock are allowed to feed outdoors consuming wild vegetation. The direction and magnitude of grazing impacts on ecosystem properties depends on grazing management such as stocking density, grazing duration and grazer species[6]. Here, grazed peatlands (comprising different management intensities and levels of drainage) are compared to mowed peatlands.

o    No burning. Burning is a routinely vegetation management practice conducted in some in some areas with the objective of stimulating the growth of grasses, maintaining these areas in young productive successional stages and increasing heterogeneity at the landscape scale and thus, supporting biodiversity[7]. However, peatland burning releases carbon to the atmosphere and banning this practice has been suggested as a measure to reduce GHG emissions.

o    Low intensity farming comprises a wide variety of farming practices analysed together and that refer mainly to the maintenance of permanent and extensive grasslands and fallowing in peatlands, including extensive livestock grazing, mowing and the lack of fertiliser inputs[8].

Key descriptors

·         These fiches focus on peatlands and the management practices conducted in these ecosystems. However, some of these farming practices are also explored more broadly without distinguishing the habitat type devoted to agricultural use in other sets of fiches (i.e, organic fertilisation and grazing fiches).

·         This review does not include peatland conservation or restoration, which are assessed in separate sets of fiches (i.e., peatland conservation and restoration).

Impact

Metric

Intervention

Control

Positive

Negative

No effect

Uncertain*

Increase biodiversity

No burning

Burning

0

0

0

1 (0)

Decrease GHG emissions

CH4 emission

Grazing

Mowing

0

0

1 (1)

0

Low intensity farming

High intensity farming

0

0

1 (1)

0

No fertilisation

Fertilisation

0

0

1 (1)

0

N2O emission

Low intensity farming

High intensity farming

0

0

1 (1)

0

No fertilisation

Fertilisation

1 (1)

0

0

0

Increase soil biological quality

No fertilisation

Fertilisation

0

1 (1)

0

0

Increase crop yield

No fertilisation

Fertilisation

0

1 (1)

0

0

Keywords

TS=("wetland*" OR "marsh*" OR "fen*" OR "peatland*" OR "carbon-rich soil*" OR "carbon rich soil*" OR "wet meadow*" OR "wet soil*" OR "peat layer*" OR "water table*" OR "water layer*" OR “peat swamp*” OR “peat*” OR “water-saturated soil*” OR “black water*” OR “floodplain*” OR “histosol*” OR “mire*” OR “organic soil*” OR “estuar*” OR “mudflat*” OR "bog*") AND TS= ("rewett*" OR "land use change*" OR "land-use change*" OR "conserve*" OR "preserv*" OR "restor*" OR "conver*" OR "drain*" OR "undrain*" OR "protect*" OR "water retention" OR "colonization W/4 Thyfa" OR "colonization W/4 Sphagnum" OR "colonisation W/4 Thyfa" OR "colonisation W/4 Sphagnum" OR "set aside" OR “dry-rewet*” OR “irrigat*” OR “reveget*”) AND TS=("meta-analy*" OR "systematic* review*" OR "evidence map*" OR "global synthes*" OR "evidence synthes*"  OR "research synthes*")

AND

TS=("wetland*" OR "marsh*" OR "fen*" OR "peatland*" OR "carbon-rich soil*" OR "carbon rich soil*" OR "wet meadow*" OR "wet soil*" OR "peat layer*" OR "water table*" OR "water layer*" OR “peat swamp*” OR “peat*” OR “water-saturated soil*” OR “black water*” OR “floodplain*” OR “histosol*” OR “mire*” OR “organic soil*” OR “estuar*” OR “mudflat*”) AND TS= ("plough*" OR "till*" OR "drain*" OR "water use" OR "machinery" OR "integrated pest management*" OR "IPM" OR "fertilis*" OR "fertiliz*" OR "paludicult*" OR "extensive W/4 management*" OR “burn*” OR “sustainable W/4 management*” OR “traditional W/4 management*” OR “prevention W/4 inva*” OR “eradication W/4 inva*” OR “control w/4 inva*” OR “graz*” OR “afforest*”) AND TS=("meta-analy*" OR "systematic* review*" OR "evidence map*" OR "global synthes*" OR "evidence synthes*"  OR "research synthes*")

or

(SUBJAREA(AGRI OR ENVI) AND TITLE-ABS-KEY("wetland*" OR "marsh*" OR "fen*" OR "peatland*" OR "carbon-rich soil*" OR "carbon rich soil*" OR "wet meadow*" OR "wet soil*" OR "peat layer*" OR "water table*" OR "water layer*" OR “peat swamp*” OR “peat*” OR “water-saturated soil*” OR “black water*” OR “floodplain*” OR “histosol*” OR “mire*” OR “organic soil*” OR “estuar*” OR “mudflat*” OR "bog*") AND TITLE-ABS-KEY("rewett*" OR "land use change*" OR "land-use change*" OR "conserve*" OR "preserv*" OR "restor*" OR "conver*" OR "drain*" OR "undrain*" OR "protect*" OR "water retention" OR "colonization W/4 Thyfa" OR "colonization W/4 Sphagnum" OR "colonisation W/4 Thyfa" OR "colonisation W/4 Sphagnum" OR "set aside" OR “dry-rewet*” OR “irrigat*” OR “reveget*”) AND TITLE-ABS-KEY("meta-analy*" OR "systematic* review*" OR "evidence map*" OR "global synthes*" OR "evidence synthes*" OR "research synthes*"))

AND

(SUBJAREA(AGRI OR ENVI) AND TITLE-ABS-KEY("wetland*" OR "marsh*" OR "fen*" OR "peatland*" OR "carbon-rich soil*" OR "carbon rich soil*" OR "wet meadow*" OR "wet soil*" OR "peat layer*" OR "water table*" OR "water layer*" OR “peat swamp*” OR “peat*” OR “water-saturated soil*” OR “black water*” OR “floodplain*” OR “histosol*” OR “mire*” OR “organic soil*” OR “estuar*” OR “mudflat*”) AND TITLE-ABS-KEY("plough*" OR "till*" OR "drain*" OR "water use" OR "machinery" OR "integrated pest management*" OR "IPM" OR "fertilis*" OR "fertiliz*" OR "paludicult*" OR "extensive W/4 management*" OR “burn*” OR “sustainable W/4 management*” OR “traditional W/4 management*” OR “prevention W/4 inva*” OR “eradication W/4 inva*” OR “control w/4 inva*” OR “graz*” OR “afforest*”) AND TITLE-ABS-KEY("meta-analy*" OR "systematic* review*" OR "evidence map*" OR "global synthes*" OR "evidence synthes*" OR "research synthes*"))

Search dates

No time restrictions

Databases

Web of Science and Scopus, run in May 2022

Selection criteria

The main criteria that led to the exclusion of a synthesis paper were when the paper: 1) did not deal with peatlands or carbon-rich soils or the effects on peatlands could not be disentangled from those on wetlands; 2) was either a non-systematic review, a non-quantitative systematic review, or a meta-regression without mean effect sizes; 3) was not written in English. Synthesis papers that passed the relevance criteria were subject to critical appraisal carried out on a paper-by-paper basis.

The search returned 471 synthesis papers potentially relevant for the practices object of our fiche. From the 471 potentially relevant synthesis papers, 332 were excluded after reading the title and abstract, and 135 after reading the full text according to the above-mentioned criteria. Finally, 4 synthesis papers were selected for peatland management.

1

Chen, M; Chang, L; Zhang, J; Guo, F; Vymazal, J; He, Q; Chen, Y

2020

Global nitrogen input on wetland ecosystem: The driving mechanism of soil labile carbon and nitrogen on greenhouse gas emissions

ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY, 4, 100063.

10.1016/j.ese.2020.100063

2

Haddaway, NR; Burden, A; Evans, CD; Healey, JR; Jones, DL; Dalrymple, SE; Pullin, AS

2014

Evaluating effects of land management on greenhouse gas fluxes and carbon balances in boreo-temperate lowland peatland systems

ENVIRONMENTAL EVIDENCE, 3(1), 1-30.

10.1186/2047-2382-3-5

3

Valkama, E; Uusitalo, R; Ylivainio, K; Virkajarvi, P; Turtola, E

2009

Phosphorus fertilization: A meta-analysis of 80 years of research in Finland

AGRICULTURE ECOSYSTEMS AND ENVIRONMENT, 130, 75-85.

10.1016/j.agee.2008.12.004

4

Stewart, GB; Coles, CF; Pullin, AS

2005

Applying evidence-based practice in conservation management: Lessons from the first systematic review and dissemination projects

BIOLOGICAL CONSERVATION, 126, 270-278.

10.1016/j.biocon.2005.06.003