Flood cropland when fallow to conserve freshwater marshes

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study evaluated the effects, on freshwater marsh vegetation, of flooding cropland during fallow seasons or years. The study was in Brazil.


  • Community composition (1 study): One replicated, site comparison study in Brazil found that flooding rice fields during their fallow period affected the overall community composition of wetland plants, but that the nature of the effect depended on when fields were surveyed.
  • Overall richness/diversity (1 study): The same study found that flooding rice fields during their fallow period had no significant effect on wetland plant species richness per site and per survey, although fewer species were recorded in the flooded fields over the year of the study.




About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, site comparison study in 2005–2006 of six rice fields in southern Brazil (Rolon & Maltchik 2010) found that rice fields that were flooded when fallow contained a different wetland plant community to rice fields that remained drained when fallow, but with similar species richness and biomass. The overall wetland plant community composition in the rice fields depended on the combination of flooding regime (whether fields were flooded or drained when uncultivated) and survey period (whether fields were cultivated or fallow when surveyed; data reported as a graphical analysis). Flooded and drained fields supported statistically similar species richness (flooded: 4–12 species/1.5 m2/survey; drained: 2–15 species/1.5 m2/survey) and biomass (flooded: 1–85 g/m2/survey; drained: 1–35 g/m2/survey) of wetland plants. However, only 22–31 different wetland plant species were recorded in flooded fields over the study year, compared to a total of 31–44 in drained fields. Methods: Between June 2005 and June 2006, wetland vegetation was surveyed in six rice fields (six 0.25-m2 quadrats/field/survey). Surveys covered all stages of the rice cultivation cycle, including cultivated (field preparation and rice growth) and uncultivated (post-harvest and fallow) periods. All fields were flooded when cultivated. During the uncultivated periods three of the fields were flooded and three were drained. Above-ground vegetation collected from each quadrat was dried before weighing.

    Study and other actions tested
Please cite as:

Taylor N.G., Grillas P., Smith R.K. & Sutherland W.J. (2021) Marsh and Swamp Conservation: Global Evidence for the Effects of Interventions to Conserve Marsh and Swamp Vegetation. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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Marsh and Swamp Conservation

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation
Marsh and Swamp Conservation

Marsh and Swamp Conservation - Published 2021

Marsh and Swamp Synopsis

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