UGent student Lisa Van Langenhove and her mentors discovered that trees along these slopes displayed more and more leaves as years passed by. The scientists looked at 12 climbs on images between 1980 and 2016. Before 1990 few trees had leaves. After that year hawthorns, birches and hornbeams all had leaves. Average temperatures rose by 1.5°C over this period.

Trees with more leaves mean greater shade below them and this too impacts on nature throwing up problems: flowers don't get a chance to blossom, inspects go without nectar and birds find no prey. Prof Pieter De Frenne, a cycling enthusiast: "For the trees it can mean good news: they produce more wood. For animals and plants underneath it's bad news."

