During a rather cold picnic last week I tried to spot the winner in the annual oak before ash race. Between late March and early May both trees bud and show first leaf. With May feeling like March in the Lake District this week it came as no surprise that both trees where having a slow start this spring.
The folklore goes something like this:
If the oak before the ash,Then we’ll only have a splash, If the ash before the oak, Then we’ll surely have a soak.
Looking more closely, oak seemed to be the winner on the banks of the river Kent. Checking out naturescalendar.org.uk shows oak to be winning across the UK. Research over the last thirty years shows oak to be the clear winner in most years, and recently oak has been budding two weeks earlier than thirty years ago.
Why is this happening? Climate change is making the race to bud much more unequal between these two species. Oak, quite simply, is the climate change winner. For every one degree increase in temperature the oak gets four days advantage over the ash. Because the oak gets there quicker, it achieves a larger canopy size and dominates the woodland. This change in timing in turn changes the landscape we see around us. With additional pressure from ash-die-back (also known as Chalara, caused by the fungus Hymenoscyphus fraxineus) ash trees are really under pressure.
Changes to the timing of budding and leaf growth also has a knock on impact on the birds and insects living in our woodlands. With food sources out of sync with the animals and birds that depend on them the whole ecosystem can be disrupted species must adapt, migrate to more favourable conditions or populations will suffer. Change in our climate is moving at a pace that is hard to adapt to in time, and migration is not always feasible. I wonder how our poet laureate Carol Ann Duffy would express how climate change has skewed this annual species race?