Assessment Notes

Justification

This culturally significant edible species has a high level of domestic use, high commercial value, and a restricted and fragmented habitat. It is indiscriminately over-exploited, which is inferred to be one of the causes of its declining population. In addition, it faces continuing habitat loss and fragmentation. Fire has destroyed forest in a significant portion of its distribution and continues to be a major concern.

It is inferred to have undergone a population decline exceeding 50% within the last three generations (50 years) due to the above threats, which in the case of exploitation are intensifying. It is therefore suspected that the population will continue to decline at at least the same rate into the future. It therefore qualifies as Endangered A2cd+3cd+4cd.

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Geographic range

This species is found in south-central and southern Chile; it has been collected from south of Talca to Osorno. Its AOO is 1500 km² (based on the total sizes of forest patches with suitable habitat) and its EOO is 69281 km².

It is restricted to Valdivian rainforest in the coastal mountain range of Nahuelbuta with a few collections in its northern distribution in the Andean foothills. It is has never been found in Argentina, and is not expected to be as Valdivian rainforest does not occur there. Argentina has also been more surveyed for fungi than Chile and this large, conspicuous, popular edible species would have been noticed.

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Population and Trends

The population has declined more than 50% in the last 50 years (three generation lengths of this species). This is inferred through lower harvest yields based on market impressions. There are around 20 known localities, although more are suspected. Habitat loss and quality also account for declining populations. Further pressure and population reductions are expected in the near future, these are also likely to exceed 50% decline within three generations.

Population Trend: decreasing

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Habitat and Ecology

This species is ectomycorrhizal with Nothofagus species, growing alone or in small groups on soil. It forms mushrooms in early Autumn. 

It has been recorded in soil and litter under Nothofagus, particularly N. obliqua, N. dombeyi, N. alpina, N. glauca. It is frequently observed in Coihue-Roble forests.

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Threats

A major threat is over-exploitation for human consumption. This species is a large edible mushroom (up to 30 cm and 5 kg) with a high commercial value. It is sold fresh locally and is traded nationally. The mushrooms are harvested unsustainably, with large portions of mycelium attached, while immature. The previous high abundance has been observed to have decreased. Additionally, this species is associated with a reduced and fragmented Nothofagus forest. Forest fires are a growing threat due to drought, particularly in the northern half of its distribution.

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Conservation Actions

Efforts are underway to spread its distribution into additional patches of forest, along with awareness-raising campaigns for it to not be harvested in an immature state or with mycelium attached. Studies to understand adequate harvest methods for low impact on the mycelium have been carried out and are continuing.

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Use and Trade

This is a culturally important fungus, that defines the gastronomic identity of the Mapuche people. It is harvested for domestic consumption and ever-increasing commercial trade in local freemarkets. It is not possible to grow in cultivation. Demand in the capital has been increasing as the gastronomic scene grows.

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Source and Citation

Furci, G. 2019. Butyriboletus loyo. The IUCN Red List of Threatened Species 2019: e.T75099337A75099440. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T75099337A75099440.en .Accessed on 5 February 2025

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• Country occurrence