Data extracted in September 2021
Fiche created in December 2023

Note to the reader: This general fiche summarises all the environmental and climate impacts of GRASSLAND CONSERVATION AND RESTORATION found in a review of 10 synthesis 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. The impacts reported here are those for which there is scientific evidence available in published synthesis papers, what does not preclude the farming practice to have other impacts on the environment and climate still not covered by primary studies or by synthesis papers.

The synthesis papers review a number of primary studies ranging from 13 to 259. Therefore, the assessment of impacts relies on a large number of results from the primary studies, obtained mainly in field conditions, or sometimes in lab experiments or from model simulations.

1.      DESCRIPTION OF THE FARMING PRACTICE

• Description:
  • Grasslands are areas of land predominantly covered by communities of grass-like plants and forbs and may include sparsely occurring trees and shrubs. In the Eurostat classification, percentages of area covered by such canopies are limited to less than 10 % in the case of trees and to less than 20 % in the case of shrubs (i.e., low woody plants capable of reaching heights of up to 5 metres)[2] or shrubs and trees together.[3] However, in the scientific literature reviewed here, grasslands are usually more broadly defined and might not fully meet such canopy limits. 
  • This review includes a wide variety of grassland types: savannah, grassy deserts, seasonally flooded grasslands, prairies, meadows, pastures, rangelands, salt-marshes, bioenergy perennial grasslands, calcareous grasslands and wooded grasslands. Grasslands differ in terms of: management intensity (natural, semi-natural, improved and intensively managed); management history: permanent and temporary; successional stage (old successional and secondary grasslands); biomes and climates (semi-arid, temperate, tropical, Mediterranean, tundra, alpine, subalpine, artic and subartic).
  • Fodder crops are not included as grasslands.
  • Grassland conservation refers to the preservation (i.e., no transformation to other land uses) of old successional natural grasslands. Old successional natural grasslands are grasses and forbs communities with no major human-induced structural or functional alterations so that their current management closely resembles historical, endogenous disturbance regimes (e.g., grazing intensity and fire frequency).[4] In the scientific literature, these ecosystems are also referred as old-growth, ancient, remnant or native grasslands.
  • Grassland restoration includes active and passive restoration methods usually aiming at enhancing plant community diversity, what is then expected to have cascading positive effects in higher trophic levels.[5]
  • This review includes several restoration methods: sowing of seed mixtures, addition of soil and hay, reintroduction of grazing and burning as active restoration methods, and abandonment of agricultural use as passive restoration method. In this review, we only consider the restoration of former grassland areas degraded by agricultural use (i.e., degradation due to mining or other land uses are excluded). We define secondary grasslands as the herbaceous communities that assemble after destruction (here, by agricultural use) of old successional natural grasslands, where the restoration efforts are conducted
• Key descriptors:
  • For the exploration of grassland conservation, this review includes the spatial comparison between preserved old successional natural grasslands (intervention) and nearby secondary grasslands, either restored or degraded, as comparator. 
  • For the exploration of grassland restoration, this review includes spatial and temporal comparisons between restored grasslands (intervention) and croplands or secondary grasslands after crop abandonment as controls. Spatial comparisons are those conducted simultaneously between restored grasslands and nearby croplands (or secondary grasslands after crop abandonment). Temporal comparisons are those conducted in the same site before (when land use was cropland or abandoned cropland) and after restoration into grassland. 
  • In this review, grassland restoration includes restoration into different types of grasslands, including perennial bioenergy grasslands. 
  • This review does not include grazing or other management practices (i.e, soil amendment and fertilisation, mowing, increasing grass species richness) conducted in grasslands, which are assessed in separate sets of fiches. 
    

2.     EFFECTS OF THE FARMING PRACTICE ON CLIMATE AND ENVIRONMENTAL IMPACTS

We reviewed the impacts of the conservation of old successional natural grasslands compared to secondary grassland and the restoration of grasslands in replacement of croplands or of secondary grasslands.

The table below shows the number of synthesis papers with statistical tests reporting i) a significant difference between the Intervention and the Comparator, that is to say, a significant statistical effect, which can be positive or negative; or ii) a non-statistically significant difference between the Intervention and the Comparator. In addition, we include, if any, the number of synthesis papers reporting relevant results but without statistical test of the effects. Details on the quality assessment of the synthesis papers can be found in the methodology section of this WIKI.

Out of the 10 selected synthesis papers, 9 included studies conducted in Europe, and 10 have a quality score higher than 50%.

Table 1: Summary of effects. Number of synthesis papers reporting positive, negative or non-statistically significant effects on environmental and climate impacts. The number of synthesis papers reporting relevant results but without statistical test of the effects are also provided. When not all the synthesis papers reporting an effect are of high quality, the number of synthesis papers with a quality score of at least 50% is indicated in parentheses. Some synthesis papers may report effects for more than one impact, or more than one effect for the same impact.

3.      FACTORS INFLUENCING THE EFFECTS ON CLIMATE AND ENVIRONMENTAL IMPACTS

The factors significantly influencing the size and/or direction of the effects on the impacts, according to the synthesis papers included in this review, are reported below. Details about the factors can be found in the summaries of the meta-analyses available in this WIKI.

Table 2: List of factors reported to significantly affect the size and/or direction of the effects on environmental and climate impacts, according to the synthesis papers reviewed. The reference number of the synthesis papers where those factors are explored is given in parentheses.

4.     SYSTEMATIC REVIEW SEARCH STRATEGY

Table 3: Systematic review search strategy - methodology and search parameters.

5.     SYNTHESIS PAPERS INCLUDED IN THE REVIEW

Table 4: List of synthesis papers included in this review. More details can be found in the summaries of the meta-analyses.

Disclaimer: These fiches present a large amount of scientific knowledge synthesised to assess farming practices impacts on the environment, climate and productivity. The European Commission maintains this WIKI to enhance public access to information about its initiatives. Our goal is to keep this information timely and accurate. If errors are brought to our attention, we will try to correct them. However, the Commission accepts no responsibility or liability whatsoever with regard to the information on these fiches and WIKI.

[1] Synthesis research papers include either meta-analysis or systematic reviews with quantitative results. Details can be found in the methodology section of the WIKI.

[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.

[5] Sexton & Emery. 2020. Grassland restorations improve pollinator communities: a meta-analysis. Journal of Insect Conservation 24, 719–726.