CORVALLIS, Ore. — The harvesting of peat moss used by gardeners and the nursery industry to improve drainage and retain water in soil contributes to climate change, according to an Oregon State University Extension Service soil scientist.
Once removed from bogs, peat moss dries quickly and is processed into soil amendments to improve drainage and moisture retention.
“Bogs represent 5% of the Earth’s surface and yet they contain more carbon than all the planet’s forests combined,” said Linda Brewer, soil scientist in Oregon State’s Department of Horticulture in the College of Agricultural Sciences.
Peat moss is harvested from bogs and fens around the world, primarily in Canada and Russia. These waterlogged ecosystems have sequestered carbon for 10,000 to 12,000 years. When harvested, that carbon is released back into the atmosphere, contributing to climate change. Harvesting also destroys a native habitat essential to birds, reptiles, insects and small mammals.
“It’s a huge storage unit for carbon dioxide,” Brewer said. “As soon as we start tinkering with it, carbon is released.”
How peat moss is used
Once removed from bogs, peat moss dries quickly and is processed into soil amendments to improve drainage and moisture retention. Many bagged soils contain peat moss, and some gardeners add it to their own mixes.
However, peat moss has drawbacks: it is low in nutrients, has a low pH and is not attractive to essential soil microbes. Compost offers an alternative that feeds microbes, improves drainage and retains water, though it decomposes more quickly, Brewer said.
England will ban the sale of peat moss starting in 2024 because of environmental concerns. Peat develops in bogs so wet they lack free oxygen, slowing decomposition. “It’s like a pickling process,” Brewer said. “The highly acidic conditions in the bog preserve organic matter.”
Layers of peat
Peat moss, in the genus Sphagnum, forms in three layers that can reach several meters in depth:
- The bottom zone contains the oldest, most decomposed material.
- The middle zone has partially decomposed moss.
- The thin top layer consists of living moss.
Peat used in horticulture is typically harvested from the middle layer. Dried sphagnum moss from the top layer is sold as a decorative product for floral arrangements and crafts.
Environmental costs of harvesting
Peat has been used as fuel for centuries, but large-scale agricultural use expanded after World War II. Nurseries, which consume large quantities of peat, often sanitize and reuse it. Harvested bogs may be replanted, but it can take 30–40 years before they stop releasing carbon. In some cases, peat companies drain and clear-cut bogs to reach the moss, destroying native habitat.
“You could call harvesting peat renewable because some bogs are being replanted, but it takes centuries for them to fully recover,” Brewer said. “The damage has been done and is continuing. It’s not eco-friendly.”
Searching for alternatives
Nurseries and gardeners are looking for substitutes. Coconut coir — a fiber harvested from coconuts — is the closest replacement, though transporting it requires fossil fuels. Brewer also recommends compost, decomposed manure, wood chips, leaves and perlite, a product made from lava deposits.
Concerned consumers should check bagged soil amendments to see if they contain peat moss, Brewer said.
Previously titled Harvesting peat moss contributes to climate change, Oregon State scientist says
