Increasing public scrutiny has questioned whether the use of peat is environmentally sustainable. A new review According to Dr. James Altland, research director of the USDA’s Agricultural Research Service, and Dr. Bruce Bugbee of Utah State University, they present a more nuanced picture than much of the current evidence portrays.
“Much of the debate in the popular press suggests that the use of peat in horticulture is unsustainable because it causes global warming and other environmental impacts,” shares James. “We have seen that agriculture is much more sustainable than some parties in the media want us to believe.”
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Differences between regions matter
The review states that assessments of peatland sustainability should differentiate between regions. While European peatlands have been heavily impacted by centuries of drainage and peat extraction, most Canadian peatlands remain undisturbed, with only a small proportion used for horticulture. According to the authors, this distinction is important when assessing the environmental impact of peat production.
“Currently, Canadian peatlands are sequestering carbon faster than the rate of extraction from container crop production. At current rates of extraction and with appropriate restoration, peatland use in North America is environmentally sustainable.”
The authors note that horticultural peat extraction in Canada accounts for only a small fraction of the total peatland area and that harvested sites are routinely restored after production.
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Restoration supports long-term recovery
The paper highlights the role of restoration practices, particularly the Moss Layer Transfer Technique (MLTT), in restoring peat-forming ecosystems.
“Restoration techniques, such as the moss layer transfer technique, can turn harvested peatlands into carbon sinks over decades,” he added. The review found that restored peatlands can restore vegetation, biodiversity and carbon sequestration functions over time, while improvements in water storage and hydrological performance are also documented.
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Alternatives also have environmental impacts
The researchers also looked at published life cycle assessments comparing them to substrates such as peat, korea, wood fiber, perlite and rock wool. “Life cycle assessments show that alternative substrates often have environmental impacts comparable to or greater than peat, especially when considering water use, transport and fertilizer inputs.”
The review concludes that comparisons depend on system limitations and assumptions, and that broad claims that alternatives are inherently more sustainable than peat are not consistently supported by published analyses.
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Figure A: Global carbon storage in natural systems (Gt, gigatons)
(Hirschler and Osterburg, 2022; Cleary et al, 2005; IPCC, 2023)
Performance remains an important consideration
Beyond sustainability, the paper reviews the functional characteristics that have made peat the reference substrate for container production.
“Soil’s high cation exchange capacity, water retention and stability support optimal plant growth and nutrient uptake,” shares James. The authors point out that these properties contribute to efficient irrigation and fertilizer management, maintaining good root zone conditions.
Although wood fibers, coir, and other materials can reduce peat use in mixes, each introduces its own management considerations, such as nutrient immobilization, water use, or processing requirements.
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Figure B: Annual carbon flux from human activities and sequestration through natural processes (Gt CO2-eq per year)
(Hirschler and Osterburg, 2022; Cleary et al, 2005; IPCC, 2023)
Managing future demand
As the global demand for soilless growth media is expected to increase significantly in the coming decades, the authors believe that a variety of substrate materials will be required.
“At current rates of extraction and with appropriate restoration, peat use in North America is environmentally sustainable and remains essential for horticulture and urban greening.”
For more information:
US Department of Agriculture
James Altland, Head of Research
Application Technologies Research Unit
(email protected)
www.usda.gov