Effects of CO2 Increase

Every June now, or so it seems, we see the billowing green biomass of trees and bushes on around the countryside. How much of this comes with their natural maturity, and how much from the extra CO₂ in the air? It’s probably safe to say that rising warmth and levels of the gas are, indeed, boosting the annual production of leaves and branches, just as science predicts. A satellite study of Earth’s chlorophyll reflections found that Ireland, like Britain and the rest of northern Europe, is 12% greener than it was 20 years before. The more leaves there are, the more carbon they soak up in photosynthesis and later lock away in withered litter, humus and the soil. The stored carbon eventually goes back into the air as soil organisms break down the humus and oxidise the carbon into CO₂, completing a big part of Earth’s carbon cycle – a race, as it has now become, between our production of the gas and the planet’s capacity to cope with it.

Hare
ŠMichael Viney

CO₂ is used directly in photosynthesis, and more of it can help some perennial plants to use water more efficiently and get larger more quickly. But while warming has lengthened the growing season of grassland, with virtually year-round growth promised for the south-west, the effect of extra CO₂ is mainly to change the mix of plants underfoot by enhancing the growth of herbs and clovers – quite a plus for nature, if only the sward were allowed to grow and flower.

Benefits to farming from extra warmth and CO₂ would mean little without water. In the south-east, the predicted droughts may last for several years, parching grassland brown where it cannot be irrigated. The potato has been singled out as a potential casualty of drought in eastern counties. A drier, warmer landscape will bring changes to wildlife, too. In the north-east, for example, a switch to cereal farming may lead to expansion of the long-eared European brown hare at the expense of the native Irish hare (the European animal, introduced to Ireland in the 19th century, is already dominating hare populations in some parts of mid-Ulster).

Red Squirrel

Red squirrel

Courtesy of the Department of the Environment, Community and Local Government

Red Squirrel
Courtesy of the Department of the Environment, Community and Local Government

Red Squirrel

Red squirrel

Courtesy of the Department of the Environment, Community and Local Government

Enlarge image

Grey Squirrel

Grey squirrels are not native to Ireland, but originally came from the forests of eastern North America. The Irish population originated from a single introduction in 1911, at Castle Forbes in Co. Longford.

Copyright John Kennedy

Grey Squirrel
Copyright John Kennedy

Grey Squirrel

Copyright John Kennedy

Enlarge image

Where drought is not a problem, greater warmth could boost the growth of our oakwoods and lead to more regular production of acorns. This would help not only to fill the gaps in native woods, but provide bigger numbers of little mammals, such as the woodmouse, and so rebuild populations of woodland predators, owls among them. It might also make control of the alien grey squirrel - a great consumer of acorns and continuing threat to populations of our native red squirrel - even more difficult.