Last week was Vappu, when Finns celebrate the coming of Spring. They do this in the traditional way, of drinking too much and going for a picnic the following day. But spring is only just arriving. Although the temperatures have risen and the snow has (finally) melted, and we still waiting for summer to start.
The last of the snow, now gone.
The last few weeks have been strange for someone from further south: it has got warmer, the birds have returned and started singing a wider repertoire than “I’m hungry” and “Look out for the cat!”, but still many of the plants think it is winter. The grass has not started to grow, and the trees are still stark
Look, ma, no leaves!
In the last few days, some have started to produce buds. The birds, though, have been arriving for several weeks: driven by their own tendencies to migrate from warmer climes. In the next week or two Finland will change from the stark beauty of trunks and branches to a greener, more luxuriant world that is beautiful in a very different way.
Not all of these species are native to Finland.
But now we have to wait, and the waiting seems to be getting longer. Climate change has given us winters that are less severe, so that the snow melts earlier. For the birds, too, spring is moving: they are arriving earlier and earlier, as they respond to a warming climate1. But many plants are not responding. They follow the rhythms of the sun, being awakened by the early morning sunlight, as they measure the shortening of the night. For them, the only response is evolutionary: plants that are programmed to respond earlier will have to disperse their seeds further north if they are to track the climate.
It is difficult to see what the outcome of this will be. Some species – birds and some plants – will be able to track the warming climate by changing their behaviour. But although they will find themselves moving into areas where the climate is benign, much of the vegetation will only awaken later. Those sleepy plants will also face problems: plants that can respond earlier will be able to adapt. Similarly, populations of plants with shorter life cycles can respond more quickly than trees that take many years to grow.
It is only over the last few years that we have started to grapple with the effects that climate change will have on populations and communities. We are starting to ask the pertinent questions: how fast can populations adapt? Can they migrate north2 quickly enough to track the climate? Will cuddly looking polar bears survive when their ice melts?
We understand that this brave new world is coming soon, and have a reasonable idea about how the climate will be affected. But we are only starting to come to grips with how this will affect our ecosystems. Just as with the approaching summer, we know that soon there will be large changes as the world warms up. The models are telling us that the next few decades will see a rush of changes in the climate and habitat, as temperatures and rainfall shift around the globe. We know these will mean changes to ecosystems, as plants and animals that prefer the new climate move in. The pace of change will be slower than the annual change from winter to summer, but may be almost as drastic.
Unlike the summer, we do not have past years to use as a guide to what will happen. We know that there will be changes, and in some ways this will be an exciting time to watch nature. For now, as in the Finnish spring, we are waiting to see the changes that we know are about to happen, indeed that are starting to happen. For now, though, we are waiting. And hopefully we will be prepared for what comes.
1 e.g. P Gienapp, R Leimu & J Merilä (2007) Responses to climate change in avian migration time – microevolution versus
phenotypic plasticity? Climate Research 35: 25-35. doi:10.3354/cr00712
2 Or south, for those of you without rpg in your hemisphere