Use herbicide to control problematic plants

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

20%
Certainty

20%
Harms

30%

Calculating overall effectiveness category

Background information and definitions

Herbicides are plant-killing chemicals. They can be applied to an entire peatland area, or specifically applied to individual plants (typically shrubs and trees).

Caution: Herbicides are not recommended as general conservation tool. Many are not specific to the target plant so can cause collateral damage. Many have negative effects side effects on biodiversity, the environment and human health (Pimentel et al. 1992). Accordingly, herbicide use is being reduced or banned in many countries.

Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.

_{Pimentel D., Acquay H., Biltonen M., Rice P., Silva M., Nelson J., Lipner V., Giordano S., Horowitz A. & D’Amore M. (2006) Environmental and economic costs of pesticide use. Bioscience, 42, 750–760.}

Study locations

Key messages

One study evaluated the effects on peatland vegetation of using herbicide to control problematic plants. The study was in fens.
Plant community composition (1 study): One replicated, controlled, before-and-after study in fens in the USA found that applying herbicide to shrubs (along with other interventions) changed the overall plant community composition.
Tree/shrub cover (1 study): The same study found that applying herbicide to shrubs (along with other interventions) could not prevent increases in shrub cover over time.
Overall plant richness/diversity (1 study): The same study found that applying herbicide to shrubs (along with other interventions) prevented increases in plant species richness.

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

A replicated, controlled, before-and-after study in 1986–2000 in two shrub-invaded fens in Ohio, USA (Barry et al. 2008) found that applying herbicide to shrubs (along with burning and cutting) altered plant community composition and prevented increases in plant species richness, but had no effect on shrub cover. The overall plant community composition changed significantly over time along transects with and without shrub control, but they accumulated different sets of species (data reported as a graphical analysis). Plant species richness was stable in the fen with shrub control (before: 12.8; after 14 years: 12.7 species/m²) but increased in the fen without shrub control (before: 12.5; after 14 years: 14.6 species/m²). Woody plant cover increased similarly in fens with shrub control (before: 46%; after 11 years: 62%) and without shrub control (before: 20%; after: 28%). From 1986, encroaching shrubs were managed using ad hoc herbicide application, burning and cutting. The study does not distinguish between the effects of these interventions. Three of four transects were managed in one fen (‘with shrub control’). Only one of four transects were managed in the other fen (‘without shrub control’). In summer 1986 (before shrub control began), 1999 and 2000, vegetation cover was estimated in 1 m² quadrats along the eight transects. Shrub cover was estimated from aerial photographs.
Study and other actions tested
Referenced paper
Barry M.J., Barbara A.K. & De Szalay F. (2008) Long-term plant community changes in managed fens in Ohio, USA. Aquatic Conservation: Marine and Freshwater Ecosystems, 18, 392-407.

Please cite as:

Taylor, N.G., Grillas, P. & Sutherland, W.J. (2020) Peatland Conservation. Pages 367-430 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Peatland Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Implement biosecurity measures to prevent introductions of problematic species Action Link	No evidence found (no assessment)	0	Synopsis Link
Physically remove problematic plants Action Link	Unknown effectiveness (limited evidence)	3	Synopsis Link
Exclude wild herbivores using physical barriers Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link