During my recent walks, whenever I’ve strayed beneath Beech trees, the immediate crunching of shells beneath my feet has alerted to me to just how abundant Beech seeds are this autumn. And that’s a surprise, because 2025 was recorded as a mast year for both Oaks and Beeches.

I’m sure you know but, just in case you don’t, a mast year is when trees produce enormous numbers of seeds. In Britain, such years are particularly obvious in Oak and Beech, and scientists believe the trees developed this strategy as a way of counteracting the feeding habits of creatures like deer, squirrels and Jays, and rodents. By producing more than these creatures can eat every few years, there should, in theory, be enough seeds left to grow into new trees. As the production of such large quantities of seeds requires a huge amount of energy, trees usually go through irregular cycles, of 5 to 10 years, between these masting events. So, to see the Beeches having two mast years in succession seems highly unusual.

I felt like I was sliding rapidly down a rabbit hole when I began googling ‘what factors contribute to a Beech mast year’ but I did notice an interesting article on the Oxford Academic website about research done in Sweden in the early 2000s into ‘mast year frequency, mast crop size and the relationships between mast year and climatic variables’. Their analysis showed that

while the average mast year interval was 4–6 years from the end of the seventeenth century up to the 1960s, the mean interval has decreased to 2.5 years during the most recent 30 years, and there have been two consecutive mast years on two occasions during this later period. Mast years have often followed years in which the temperature in July and September was higher than the 30-year mean. However, there were significant variations in the amounts of beechnuts produced between different mast years, and beechnut production increased with increasing site index. Climatic changes, especially increases in temperature, may have been responsible for the higher frequency of mast years, but increased atmospheric nitrogen deposition may also have been a contributory factor.

And it seems that scientific research by the Department of Conservation in my New Zealand homeland, supports the theory that ‘Masts are triggered by a summer that is warmer than the previous one’. There, Beech mast years can create huge problems for the survival of New Zealand’s iconic native birds, because the populations of invasive non-native predators like rats increase dramatically through their consumption of Beech seeds, so the Department of Conservation tries to predict mast years in order to manage predator numbers.

I’m going to stop now before I disappear forever down that research rabbit hole. Two things seem clear – our changing climate is affecting our trees and, if each summer is hotter than the previous year, we may well see Beech mast years much more often.