There are multiple factors involved with both collapses. Chestnut trees were planted in dense clusters in parks and along streets so their growth intermingled.

There are multiple factors involved with both collapses. Chestnut trees were planted in dense clusters in parks and along streets so their growth intermingled. This extreme unnatural density enabled pathogens to spread. Carrier pigeons were delicious and easy eating. Rampant hunting had already crashed the population at that time.