Climate Change: Phenological Mismatch

Climate change is such a dramatic process with so many varied effects that it is easy to overlook ones which are not intuitive. One such is phenological mismatch. The phrase alone is quite offputting. Derived from the word phenomenon phenology refers to the study of natural cycles and seasons with particular reference to fauna and flora. The reason this has taken on new relevance is that climate change is impacting fauna and flora at different rates such that the pre-existing balance and harmony is thrown out of kilter. A few examples highlight the issue, with my thoughts added.

Spider orchids. These plants rely on attracting solitary male bees by releasing a pheromone, taking advantage of the gap between the time these male bees emerge and the later emergence of female bees. However a 2014 study found that for each Centigrade degree rise in temperature the gap between the emergence of male and female bees shrank by 6.6 days and the orchid is likely to become threatened. [In this instance it seems difficult for the plant to adapt to the changing situation except by becoming even more attractive to the male bees while the bees have no need to adapt unless there is some unconnected reasons as to why the male bees emerge some time before the females.]

The European pied flycatcher. These birds timed their migration from Africa to their European breeding grounds such that the chicks emerged just as winter mouth caterpillars were feeding on young oak leaves. The snag with climate change is that the birds time their departure from Africa by reference to the length of day while the leafing of oak trees is related to temperature. As Spring arrives earlier in Europe the trees leaf earlier but the flycatchers arrive at the same time as previously. [Some thoughts on this: how did any migration develop in the first place; how did the synchronisation come about; how quickly did the birds adapt to past changing climate; and is the current climate change occurring too quickly for this adaptation.]

Northern lapwing and Eurasian curlew. In the past these birds built their nests after farmers sowed their fields in Spring. With a warming climate the birds are building their nests three weeks earlier but the farmers are sowing only one week earlier and destroying their well concealed nests with eggs. [Question therefore – why are the farmers not taking advantage of the longer growing season by planting earlier still.]

West Greenland Caribou. These animals have a strictly seasonal diet; in winter the lichen on the coastal rocks and in summer the inland tundra vegetation. With climate warming the migration inland occurs a week or so earlier but the inland plants are greening up to 26 days earlier. There is a positive correlation between the mismatch and calf deaths with a possible explanation that the plants become tougher and less nutritious with the passage of time. [How long therefore will it take the caribou to adapt to the changing environment as they presumably have managed to do in the past. One would think that this could occur quite quickly.]

Image result for caribou

Snowshoe hare. The coat of this animal changes from white to brown at the end of winter to maintain its camouflage but with the changing climate snow cover is disappearing three weeks earlier but the coat is only changing one week earlier, increasing lynx kills (see picture, where the camouflage is still appropriate). [Unlike the caribou the adaptation requires a physical rather than behavioral change which at one time was thought to occur over thousands or millions of years but now thought possible within five to ten generations.]

Sources and references: USA National Phenology Network, www.usanpn.org; New York Times Climate Fwd; tasmania360.com; bbc.co.uk; www2.nau.edu

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