May - timing
Spring is arriving about two weeks earlier than it would have done 30-50 years ago and autumn is about one week later. As the climate changes, different species respond in different ways, and to different degrees and at different rates.
Spring bulbs such as snowdrops and bluebells have always benefited from their stored resources giving them a head start in spring. This means that they have been able to successfully compete with more vigorous plants such as garlic mustard and cow parsley which must wait for warmer weather before they can start to grow. With warmer conditions occurring earlier in the year these plants are beginning leaf growth much earlier and the bluebells and snowdrops are losing their competitive advantage with potential serious long-term consequences.
Many insects are also responding to the changing climate, with caterpillars appearing earlier in the spring due to warmer temperatures. Blue tits that depend on the caterpillars as an abundant source of food for their young, however, are not changing the timing of their egg laying to the same degree, meaning that they could struggle to find sufficient food to feed their young.
Similar changes in the timing of different events are also being observed in the marine environment. Some species (eg echinoderms) have moved forward their seasonal spawning cycle by four to five weeks, meaning that the peak occurrences of plankton on which larval fish depend are too early. The knock-on effects of this are felt all the way up the food chain to the top predators such as seabirds as they struggle to find sufficient food to feed their young.
