Drunken Forests: Understanding the Phenomenon of Permafrost Thaw

Image description: A "drunken forest" in Fairbanks, Alaska. Drunken forests are a phenomenon where trees lean and fall due to permafrost thaw. Image source: Brandon Lucas.

Mechanisms of Drunken Forests

Drunken forests refer to a phenomenon in which trees in boreal regions adopt a leaning posture or fall due to the thawing of permafrost. This permanently frozen soil layer serves as a stable foundation for boreal ecosystems. When permafrost thaws, the soil becomes unstable, disrupting tree growth and anchorage.

Permafrost thaw is primarily due to climate warming. Higher temperatures melt the ice contained in the soil, destabilizing tree roots. Trees, no longer finding solid support, begin to lean and eventually fall, giving the appearance of a "drunken" forest.

Mechanisms of Permafrost Thaw

Permafrost is a layer of soil, rock, or sediment that remains frozen for at least two consecutive years.

Permafrost covers one-fifth of the Earth's land surface, including 90% of Greenland, 80% of Alaska, 50% of Canada, and Siberian Russia. It contains large amounts of ice in its subsoil (up to 600 meters deep). When global temperatures rise, this ice melts, turning the soil into unstable mud.

Permafrost thaw is accelerated by increasing temperatures in Arctic and subarctic regions, which are warming twice as fast as the rest of the globe. Once destabilized, the soil loses its cohesion, causing land subsidence and tree destabilization.

Ecological Effects

Permafrost thaw releases carbon and methane, two greenhouse gases, into the atmosphere. This contributes to climate warming, creating a vicious cycle where warming leads to more thaw, which in turn releases more greenhouse gases.

Drunken forests also alter natural habitats. Animals that depend on soil stability for survival, such as reindeer and caribou, see their habitats disrupted. Changes in soil structure also affect vegetation, altering the types of plants that can grow in these regions.

Socio-Economic Consequences

Human infrastructure in Arctic regions is particularly vulnerable to permafrost thaw. Roads, buildings, and pipelines can be damaged or destroyed by soil instability, leading to high repair costs.

Local communities, often dependent on natural resources, are also affected. Hunting, fishing, and gathering become more difficult, and traditional livelihoods are threatened.

Examples of Drunken Forests

• In Siberia, vast expanses of drunken forests are visible, affecting thousands of hectares of land. Rapid landscape changes, such as in the Yakutia region, illustrate this phenomenon well.
• In the lowlands of central and western Alaska, boreal forest trees show characteristic leaning due to soil instability caused by permafrost thaw. Areas near Fairbanks are particularly affected. The boreal forests of the Northwest Territories (Canada), especially around the Mackenzie River, are affected by permafrost thaw. Trees lose their verticality due to the soggy and unstable soil.
• In Lapland, in the northern parts of Norway, Sweden, and Finland, thawing frozen soils are transforming forest landscapes where tree leaning is particularly visible.
• Coastal areas of Greenland also experience isolated cases of drunken forests, although vegetation there is sparser.