Climate change or just a late spring: what to make of the messages plants send us?
Potent: dandelions that inhaled twice as much carbon dioxide as usual increased in size, had 83 per cent more flowers, and developed even better parachutes for spreading their seeds. Illustration: Michael Viney
Towards the end of the drought that struck the west for much of early spring, a university geography professor shared with me a photograph he had taken in Connemara. It showed a remarkable vista of bog and mountain dried and bleached to an eerie ash blond. On our side of the bay, too, even lowland tracts of moor grass offered this unreal platinum sheen.
All was caused by evapotranspiration, to use the professor’s term. With some 40 rainless days from mid February to mid April, the relentless and bitter winds from the east had combed the last molecules of moisture from leaf cells of moss and moor grass, sedge and heather and even the surface fibres of the bog itself. Only gradually, now, have more natural shades of life been creeping back from the roots.
Down from the hill, meanwhile, it is floriferousness – the capacity for lots of flowers – that has been engaging my mind. Certain plants in my garden have been outdoing themselves with blossom. It started early, with winter helleborines, their flowers lavishly and durably available for floating upside down in a dish, like ethereal water lilies. Then came our one posh bush, the camellia ‘Adolphe Audusson’, smothered head to toe with big scarlet rosettes, as for a Labour convention. The primroses have been at it, too, crossed with pensioned-off polyanthus and blooming in swags and cushions under the trees.
Even – and this leaped to significance – the positively lowly weed of thale cress produced an abundant mist of its tiny white flowers where I had noticed none before. Thale cress, Arabidopsis , is the one plant whose genome is thoroughly known and is thus the laboratory test plant for everybody’s theories, like the fruit fly’s employment in animal genetics. Was this spindly cress just catching up on the spring, or sending some interesting message?
Pursuing floriferousness (and simpler synonyms) through the tangled groves of Google, I soon stumbled into the exotic world of private – even, dare I say, criminal – cultivation of cannabis. In illicit growhouses and polytunnels, an elevated level of CO2, generated by burning propane gas, acts to produce larger and juicier flower buds.
Carbon dioxide is a mainstay of a plant’s life, essential in photosynthesis for food and the construction of cells. At 0.039 per cent (390 parts per million) of air (compared with oxygen’s 21 per cent), it seems only a trace, yet its accelerating rise in recent decades is a prime cause of climate change. It rose from 315ppm in 1959 to 385ppm half a century later. And as raising its levels in closed atmospheres increases productivity not only of pot but also of greenhouse tomatoes, flowers and other plants, the future impact on global vegetation is under intense research.
An important new finding, from scientists at the University of Kansas, is that CO2 may be just as potent as global warming in advancing the date of spring. (They have pinpointed the affected gene, indeed, in the flowering pathway of Arabidopsis .) This follows much other research showing that a world enriched in carbon dioxide will produce more and larger flowers. A recent experiment doubled the CO2 inhaled in by dandelions, which thereupon increased in size, had 83 per cent more flowers, and developed even better parachutes for spreading their seeds.
As it happens, it is the totally normal number and stature of the dandelions in my garden (quite welcome as early insect food and a golden treat for the eye) that have laid to rest any carbonised fancies about the helleborines, camellias and cresses. They must have had other reasons for showing off their flowers – the big chill and long drought prompting, perhaps, a special reproductive effort (though garden hybrids produce no viable seed).
While on CO2 I should record the new and positive findings of an Irish research team, led by Dr David Wilson, who have studied the carbon uptake of large areas of “rewetted” cutaway peatland at the Bord na Móna bog at Bellacorick, in north Mayo.
They used bulldozers and diggers to block drains and raise bare ridges of peat to create a range of habitats, some under open water. Vegetation – soft rushes, mosses and vascular plants (even lodgepole pine) – was quick to recolonise them. All the vegetated areas were carbon “sinks”, absorbing carbon dioxide, over the three years of the study, with the highest uptake by the new stretches of cottongrass. Only bare peat gave carbon out or had a warming effect on climate.
In the midlands, Bord na Móna’s cutaway bog has been rapidy colonised by birch and pine that, in drying out the soil, have actually become a source of CO2. In the west, given predicted rises in rainfall, rewetting Atlantic blanket bogs and keeping them free of trees (and peat-cutting) could, the team conclude, help to mitigate climate change.
You can download Dr Wilson’s findings at iti.ms/11ULCsd