Background
The authors state that understanding past, present and projected variations in mushroom harvest and their association with a changing climate "appears to be relevant not only from an ecological point of view but also from an economic perspective, given that some edible mycorrhizal fungi are among the world's most expensive delicacies (Hall et al., 2003)," but they say that a causal explanation of temporal variations in mushroom harvest is lacking, "because of unsystematic, incomplete fungal monitoring efforts and/or inventories of insufficient duration or resolution."

What was done
In an effort designed to do what had previously not been done in this regard, Buntgen et al. analyzed data from a field survey in which a total of 65,631 unique individual mycorrhizal mushrooms (representing 273 species) were recorded at weekly intervals from 1975 to 2006 in a 75-ha "fungus reserve" in western Switzerland, which consisted of a protected area that was home to a multi-storied, mixed-beech forest, after which they compared their results with various weather data they extracted from a gridded (0.5° latitude x 0.5° longitude) temperature and precipitation database.

What was learned
The three researchers report that there was "a significant increase in mushroom harvest from the first to the second half of the inventory period," and that "averaged over the 'early' (1975-1990) and 'late' (1991-2006) intervals, the weekly fruiting body counts increased from 42 to 88." This more-than-doubled boost in fungal harvest, as they describe it, "may be explained by improved growth conditions, not only for the ectomycorrhizal fungi but also for the host plants, as a result of recent climate change." More specifically, they write that "increasing central European temperatures during the second half of the 20th century and an associated extension of the growing season (Menzel and Fabian, 1999) may have resulted in greater availability of photosynthetic products to the fungal symbionts over longer periods, enabling higher productivity of fruiting bodies." In addition, they found a "pronounced correspondence between the reconstructed annual fruiting dates and country-wide grape harvest dates," which they say "is evidence that our mushroom inventory from a single forest plot is representative of patterns over a broader geographical scale." In fact, they note that "about 50% of the total forested area in Switzerland consists of similar beech forests, with the same ratio also occurring throughout central Europe," citing the work of Wohlgemuth et al. (2008) in this regard.

What it means
With respect to the significance of their findings, Buntgen et al. conclude their report by noting that the more-than-doubling of the number of fungal fruiting bodies they observed "represents an edible attraction for both humans and animals, affects the organic soil fraction, supports forest health, enhances biodiversity, increases terrestrial biomass turnover, and may even influence the global carbon cycle." Thus, they understandably write that the enhanced growth conditions and extended growing season that developed over the period of their study "appear beneficial from an economic as well as from an environmental perspective," which is good news for both society and the biosphere.

References
Hall, I.R., Wang, Y. and Amicucci, A. 2003. Cultivation of edible ectomycorrhizal mushrooms. Trends in Biotechnology 21: 433-438.

Menzel, A. and Fabian, P. 1999. Growing season extended in Europe. Nature 397: 659.

Wohlgemuth, T., Moser, B., Brandli, U.B., Kull, P. and Schutz, M. 2008. Diversity of forest plant species at the community and landscape scales in Switzerland. Plant Biosystems 142: 604-613.