Every living thing on earth has evolved within a particular ecosystem, and in the case of many species, survival depends on precise synchronicity with the seasons. A number of recent studies reveal climate change throwing this “complex ballet” into disarray, writes the New York Times.
“Global warming is changing [life’s] music,” the Times reports, “with spring now arriving several weeks earlier in parts of the world than it did a few decades ago.”
While “in some cases, species might simply adapt by shifting their ranges, or eating different foods,” others “are falling out of step” in a process called phenological mismatch—as when a flower blooms before its pollinator emerges from hibernation.
The Times cites the example of the already-endangered spider orchid, which pollinates through “pseudo-copulation” with a male mining bee attracted by orchid pheromones while it waits for its mate to waken from a longer winter hibernation. With spring arriving earlier, according to a 2014 study from the United Kingdom, female mining bees are emerging sooner and distracting the males from the flowers.
Also caught up in the dissonance is the European pied flycatcher. “From its wintering grounds in Africa,” writes the Times, “the bird flies thousands of miles north to Europe to lay eggs in time for the emergence of winter moth caterpillars, which appear for a few weeks each spring to munch on young oak leaves.”
By timing their arrival just right, the flycatchers have for generations ensured that their chicks hatched with a rich food source well within reach of the nest. “In a series of studies in the 2000s, however, scientists in the Netherlands showed that many flycatchers were starting to miss this narrow window.”
And then there are the caribou of western Greenland, whose diet has evolved in harmony with their sub-polar home. “In the winter, they eat lichen along the coast. In the spring and summer, they venture inland to give birth to their calves and eat the Arctic plants that grow there,” the Times states.
But Greenland is warming rapidly, and “those inland Arctic plants have been emerging earlier—with some plant species now greening 26 days earlier than they did a decade ago.” The caribou have not responded by speeding up their migration, “perhaps because their reproductive cycles respond most strongly to seasonal signals like the length of the day, whereas plants respond more strongly to local temperatures, which are rising.”
Scientists like University of California, Davis ecologist Eric Post “have documented a troubling trend in the region,” with caribou calf mortality rates seeming to rise “in years when the spring plant growth preceded the caribou’s calving season,” the Times reports. These spikes in calf mortality may be occurring because the Arctic plants are “tougher and less nutritious by the time the caribou get there and start eating them,” Post said.
“In theory, if given enough time, the caribou might eventually adjust as natural selection takes its course and favours individuals that calve earlier,” the Times states. “But with the Arctic warming faster than the rest of the globe,” Post added, “the question is whether things are changing too fast for evolution to matter.”