Phenological mismatches:
Phenological events are often synchronised between species. The classic example is a food chain comprised of the pied flycatcher (Ficedula hypoleuca), caterpillars and oak trees. Every spring, the birds produce large broods that eat vast quantities of caterpillars – the adults must deliver as many as 60 an hour over the 18 days it takes for the chicks to fledge. But caterpillars are an ephemeral resource, hatching to coincide with the emergence of oak foliage. The birds have thus evolved to breed so that their chicks hatch during maximum caterpillar abundance. The cue they take is temperature, which also precipitates leaf unfurling and caterpillar hatching.
This tightly coupled sequence is being disrupted by climate change. Even though all three events are triggered by rising temperatures, they are responding differently to warming. In some parts of Europe, birds are hatching too late to catch peak caterpillar, reducing the chicks’ chances of survival.
It is problems like these, known as phenological mismatches, that are bringing [UN Environment Programme] out in a cold sweat. We have long appreciated that phenological changes can spell trouble for individual species or pairs of species. But there is a dawning realisation that this is a widespread problem that could presage the breakdown of whole food chains or even ecosystems. “This is truly a global problem affecting plant and animal species in mountains, oceans, tropical and temperate forests and polar regions,” says Kappelle. [“How climate change is knocking natural events wildly out of sync,” Graham Lawton, NewScientist (25 June 2022, paywall)]
