IT IS perhaps the most striking example of how global warming is turning up the heat on the world鈥檚 wildlife. Across the UK, wild mushrooms are reproducing twice a year instead of the usual once, the first time climate change has been reported to affect the life cycle of any organism in this way.
Many fungus species spend their lives in the soil as a fibrous mat called a mycelium. Once a year they reproduce, forming the fruiting bodies that are the familiar caps and stools that litter forest floors. In the UK, this used to happen around September, during the onset of the British autumn. All that has changed now.
Within just 50 years, many fungi have doubled the length of their breeding season from 33 days on average to 74, according to a survey of 315 species conducted by by Alan Gange of Royal Holloway, University of London and his colleagues. Species now appear above ground in July, mainly as a result of warmer temperatures, and the scarcity of frosts means they keep breeding into December (Science, vol 316, p 71).
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More significantly, many have also switched to reproducing twice a year, fruiting once in the British spring and again in the autumn, something unheard of before temperatures began to climb in the mid-1970s. 鈥淭he most astonishing thing from our analysis is that 30 per cent of the species we looked at now fruit in May as well,鈥� says Gange.
Gange believes that the fungi used to be kept in check by sharp frosts earlier in the year. As temperatures have climbed, and the frosts disappeared, there is nothing forcing the fungi to remain dormant in the soil. 鈥淣ow the fungi grow, and with the rain in March they fruit and appear in April or May,鈥� he says.
In many respects, this dramatic change may have positive ecological effects, says Gange. 鈥淢ushrooms provide a huge food resource for insects, which themselves are food for birds,鈥� he says. Fungi also accelerate decomposition of wood and leaf matter, providing more soil nutrients for plants.
A downside is also likely, though. Some species, such as the honeytuft fungus (Armillaria mellea), are pests that can damage plants in orchards and gardens.
