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Data extracted in December 2021
Note to the reader: This general fiche summarises the environmental and climate impacts of GRASSLAND CONSERVATION AND RESTORATION found in a systematic review of 10 synthesis research papers [1]. These papers were selected from an initial number of 1022 obtained through a systematic literature search strategy, according to the inclusion criteria reported in section 4.
As each synthesis research paper involves a number of primary research papers - ranging from 13 to 259, the assessment of impacts relies on a large number of results obtained mainly in field experiments (carried out in situations close to real farming environment), and sometimes in lab experiments or from model simulations.
1. DESCRIPTION OF THE FARMING PRACTICE
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2. DESCRIPTION OF THE IMPACTS OF THE FARMING PRACTICE ON CLIMATE AND THE ENVIRONMENT
We reviewed the impacts of more diverse rotation (with two or more crops) compared to monocropping or simpler rotations.
We reviewed the impacts of the conservation of old successional natural grasslands compared to secondary grassland (Table 1) and the restoration of grasslands in replacement of croplands or of secondary grasslands (Table 2).
The tables below show the number of synthesis papers reporting positive, negative or no effect, based on the statistical comparison of the intervention and the control. In addition, we include the number of systematic reviews reporting relevant results, if any, without statistical test of the effects (“uncertain”). The numbers between parentheses indicate the number of synthesis papers with a quality score of at least 50%. Details on quality criteria can be found in the methodology section of this WIKI.
Out of the 10 synthesis papers selected, 9 reported studies conducted in Europe while one did not report the geographical origin of the studies included. All the synthesis papers have a quality score higher than 50%.
Table 1. Impacts of the conservation of old successional natural grassland compared to secondary grassland.
Impact | Positive | Negative | No effect | Uncertain |
Increase biodiversity | 2 (2) | 0 | 1 (1) | 0 |
Increase pollination | 0 | 0 | 1 (1) | 0 |
Increase carbon sequestration | 1 (1) | 0 | 0 | 0 |
Table 2. Impacts of the restoration of grassland compared to cropland or secondary grassland.
Impact | Comparator (Land use previous to restoration) | Positive | Negative | No effect | Uncertain |
Increase biodiversity | Cropland | 1 (1) | 0 | 2 (2) | 0 |
Decrease GHG emissions | Cropland | 1 (1) | 0 | 0 | 0 |
Decrease nutrient leaching and run-off | Cropland | 1 (1) | 0 | 0 | 0 |
Increase pollination | Secondary grassland | 1 (1) | 0 | 0 | 0 |
Increase soil nutrients | Cropland | 0 | 1 (1) | 0 | 0 |
Increase carbon sequestration | Cropland | 3 (3)* | 0 | 0 | 0 |
Secondary grassland | 0 | 1 (1)** | 0 | 0 |
*In one of these synthesis papers the previous cropland use is restored into perennial bioenergy grassland.
**In this review paper the previous secondary grassland use is restored into perennial bioenergy grassland.
3. DESCRIPTION OF THE KEY FACTORS INFLUENCING THE SIZE OF THE EFFECT
Only the factors explicitly studied in the reviewed synthesis papers with a significant effect are reported below. Details regarding the factors can be found in the Summaries of the meta-analyses.
Impact | Factors |
Increase biodiversity | Age of secondary grassland (ref 2), Presence of remnant vegetation (ref 9) |
Increase pollination | Pollinator taxa (ref 3), Time since treatment (ref 3), Restoration method (ref 3) |
Increase carbon sequestration | Abandonment time (ref 6), Climate (ref 6), Initial soil organic carbon stock (ref 6), Soil sampling depth (ref 11) |
4. SYSTEMATIC REVIEW SEARCH STRATEGY
Keywords | TS=("grazing*" OR "grassland*" OR "pasture*" OR "rangeland")) AND TS=(("meta-analy*" OR "systematic* review*" OR "evidence map" OR "global synthesis" OR "evidence synthesis" OR "research synthesis") or TITLE-ABS-KEY: ("grazing*" OR "grassland*" OR "pasture*" OR "rangeland") AND TITLE-ABS-KEY ("meta-analy*" OR "systematic* review*" OR "evidence map" OR "global synthesis" OR "evidence synthesis" OR "research synthesis") |
Search dates | No time restrictions |
Databases | Web of Science and Scopus, run in September 2021 |
Selection criteria | The main criteria that led to the exclusion of a synthesis paper were when the paper: 1) does not deal with terrestrial grasslands or the effects on grasslands can not be disentangled from other land uses; 2) does not compare old successional natural grasslands with nearby secondary grasslands (for grassland conservation); e.g., comparisons between old successional natural grasslands and croplands were excluded; 3) does not compare restored grasslands with nearby or with previous cropland use, including tree plantations (for grassland restoration); e.g., land use changes from grassland to cropland were excluded; 4) is either a non-systematic review, a non-quantitative systematic review, or a meta-regression without mean effect sizes; 4) is not written in English. Due to the high number of potentially valid synthesis papers, we applied additional exclusion criteria: 5) the paper does not include studies conducted in Europe; 6) the paper only reports impacts on crop or animal production, and no environmental impacts. Synthesis papers that passed the relevance criteria were subject to critical appraisal carried out on a paper-by-paper basis. The search returned 1022 synthesis papers potentially relevant for the practice object of our fiche. From the 1022 potentially relevant synthesis papers, 661 were excluded after reading the title and abstract, and 351 after reading the full text according to the above-mentioned criteria. Finally, 10 synthesis papers were selected for grassland conservation and restoration. |
5. LIST OF SYNTHESIS PAPERS INCLUDED IN THE REVIEW
Ref. Num | Authors | Year | Title | Reference | DOI |
1 | Zhang, YS; Pan, BB; Lam, SK; Bai, E; Hou, PF; Chen, DL | 2021 | Predicting the ratio of nitrification to immobilization to reflect the potential risk of nitrogen loss worldwide | ENVIRONMENTAL SCIENCE AND TECHNOLOGY, 55(11), 7721-7730. | 10.1021/acs.est.0c08514 |
2 | Nerlekar, AN; Veldman, JW | 2020 | High plant diversity and slow assembly of old-growth grasslands | PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 117(31), 18550-18556. | 10.1073/pnas.1922266117 |
3 | Sexton, AN; Emery, SM | 2020 | Grassland restorations improve pollinator communities: A meta-analysis | JOURNAL OF INSECT CONSERVATION, 24(4), 719-726. | 10.1007/s10841-020-00247-x |
4 | Wu, JJ; Chen, Q; Jia, W; Long, CY; Liu, WZ; Liu, GH; Cheng, XL | 2020 | Asymmetric response of soil methane uptake rate to land degradation and restoration: Data synthesis | GLOBAL CHANGE BIOLOGY, 26(11), 6581-6593. | 10.1111/gcb.15315 |
5 | Kampf, I; Holzel, N; Storrle, M; Broll, G; Kiehl, K | 2016 | Potential of temperate agricultural soils for carbon sequestration: A meta-analysis of land-use effects | SCIENCE OF THE TOTAL ENVIRONMENT, 566, 428-435. | 10.1016/j.scitotenv.2016.05.067 |
6 | Harris, ZM; Spake, R; Taylor, G | 2015 | Land use change to bioenergy: A meta-analysis of soil carbon and GHG emissions | BIOMASS AND BIOENERGY, 82, 27-39. | 10.1016/j.biombioe.2015.05.008 |
7 | MacDonald, GK; Bennett, EM; Taranu, ZE | 2012 | The influence of time, soil characteristics, and land-use history on soil phosphorus legacies: A global meta-analysis | GLOBAL CHANGE BIOLOGY, 18(6), 553-565. | 10.1111/j.1365-2486.2012.02653.x |
8 | Felton, A; Knight, E; Wood, J; Zammit, C; Lindenmayer, D | 2010 | A meta-analysis of fauna and flora species richness and abundance in plantations and pasture lands | BIOLOGICAL CONSERVATION, 143(3), 545-554. | 10.1016/j.biocon.2009.11.030 |
9 | Attwood, SJ; Maron, M; House, APN; Zammit, C | 2008 | Do arthropod assemblages display globally consistent responses to intensified agricultural land use and management? | GLOBAL ECOLOGY AND BIOGEOGRAPHY, 17(5), 585-599. | 10.1111/j.1466-8238.2008.00399.x |
10 | Guo, LB; Gifford, RM | 2002 | Soil carbon stocks and land use change: a meta analysis | GLOBAL CHANGE BIOLOGY, 8(4), 345-360. | 10.1046/j.1354-1013.2002.00486.x |
[1] Synthesis research papers include either meta-analysis or systematic reviews with quantitative results.
[2] https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Shrubland
[3] https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Grassland
[4] Nerlekar & Veldman. 2020. High plant diversity and slow assembly of old-growth grasslands. PNAS 117, 18550–18556.