The below-ground fruiting bodies of Truffles (Tuber sp.), the mycological partners in a globally distributed symbiosis with forest trees, are prized by gourmands and the lucrative industry of truffle plantation owners feeding their fungal fancy. As tree-symbionts, they are levered by foresters for their ability to increase the growth and survivability of tree-seedlings. Unfortunately, throughout the 20th century, many Truffle populations are producing markedly less of the edible fruitbodies sold commercially and used as fungal inoculum for forest restoration. This trend of declining productivity, potentially a consequence of 20th century climate changes, is particularly marked in the Périgord Truffle (T. melanosporum), which is specialised to Mediterranean climates of Southern Europe. By contrast, the more cosmopolitan Burgundy or Summer Truffle (T. aestivum), which occurs throughout Europe, has been thought to be safe from such declines in productivity due to its ability to tolerate conditions along relatively broader gradients of temperature and precipitation. Nevertheless, anecdotal evidence, courtesy of hobby Truffle foragers, suggests sites that once produced relatively large hauls of T. aestivum fruiting bodies have started to decline – or have stopped producing fruiting bodies altogether. To quantify the environmental drivers behind the timing and yield of T. aestivum fruitbody production (and their potential declines), I am working with Martina Peter, Simon Egli, and Mathias Haeni to analyse data on Truffle productivity over 3-week intervals for up to 6 continuous years in 21 sites distributed throughout Switzerland and Germany—sampling conducting by a network of citizen-scientists and their specially trained, Truffle-scenting dogs. Using machine-learning algorithms to sort out the environmental drivers of T. aestivum annual production and average fruitbody size, we find evidence for strong, non-linear relationships between soil and ground-cover variables. Additionally, preliminarily analyses suggests that frutibodies show an inter-annual trend of decreasing fruitbody size and fruitbody productivity – one that, unabated, will terminate in completely unproductive sites. Additionally, I will discuss the potential causes of this decline and future directions of research using the dataset.