There are few places in the world, if any, that aren’t touched by human activity, including places with no humans. And one of our chief human activities over the past couple of centuries has been the transfer of carbon from reservoirs deep within the planet out into the atmosphere.
We’ve been re-creating the environment during this industrial dream. Like a dream, we aren’t always conscious of our decisions and the impact they will have as we weave the story forward.
Several recent studies show that the phenology of leaves around the world, i.e. the annual cycle of vegetation changes, has dramatically altered since the mid-20th century.
It might not seem particularly important if the first vegetation leafs out a week earlier every year, or drops a week later in autumn.
But a study published in Nature Climate Change measured severe phenological changes on 54% of the planet’s land surface between 1981 and 2012, with resulting shifts for entire ecosystems.
Warmer temperatures, new rainfall patterns and increased atmospheric carbon are altering the rate of energy exchange between land and atmosphere in complex ways that we don’t yet entirely understand.
Increased carbon uptake due to earlier springs and later autumns mitigate climate change, at least in theory (and leaving out the issue of deforestation, of course).
But as it turns out, phenological change alters different forests in different ways. Temperate forests react differently from boreal forests, and the overall impact on a global level is as yet unclear.
Truly long-term studies of leaf-out times aren’t widely available, but the Marsham family of Norfolk, England, kept records of leafing and flowering times of estate woodland plants from 1736 to 1947.
By matching historical temperature records (back to 1772) to the family log, researchers at the University of Edinburgh and Biomathematics & Statistics Scotland found that while a warmer autumn causes early leafing species such as birch to take longer to come into leaf the following spring, while late-leafing species, such as oak trees, seem unaffected by autumnal temperatures.
These citizen scientist observations allow researchers to test predictions regarding the effects of temperature on leaf cycles and woodland environments.
What is clear on a global scale is that the countless organisms with life cycles synchronized to vegetation cycles are being dramatically affected.
Meanwhile, we continue to emit carbon sighs during our long industrial dream of plenty, not yet knowing where it will lead, or how the earth will look we will wake up.