Future Forests and Climate Change

This week’s launch of a pioneering new forest research facility at the University of Birmingham marks the beginning of a unique experiment to reveal how our forests are likely to react to the elevated carbon dioxide levels expected by 2050, and the potential of forest ecosystems to store carbon and thus mitigate future climate change.

Carbon dioxide (CO2) is the atmospheric gas that sets our global thermostat, controlling the complicated web of elemental cycling that defines our planet’s climate. Therefore, taking action to control climate change inevitably involves estimating future atmospheric levels of CO2.

However, predictions about future CO2 levels are tentative, largely due to uncertainty around one big environmental factor: we cannot accurately figure out how much CO2 is locked up each year in trees, soil and other organic matter – otherwise known as ‘vegetated land’.

We know this land ‘carbon sink’ is big – overall, it is responsible for taking up between one-in-three and one-in-four of the CO2 molecules released into the atmosphere by human activities – but we don’t know exactly how big, and we have even less confidence in our predictions of its capacity over the decades and centuries to come.

Predicting the extent to which land vegetation will continue to lock up carbon in future requires experiments large enough and long enough to capture the ins and outs of whole ecosystems subjected to elevated CO2.

The University of Birmingham has established a research facility that does just this, in the Free-Air Carbon Enrichment (FACE) facility within the Birmingham Institute of Forest Research (BIFoR).

As of this week, and until 2026, BIFoR FACE is testing definitively how much carbon undisturbed temperate forests can lock up, by bathing patches of oak woodland in air containing the same levels of CO2 that are predicted to be in the atmosphere by 2050.

Along with sister facilities in the Mediterranean climate of south-eastern Australia, and the wet tropical climate of the Amazon, the facility is a key cog in a global machine measuring the response of forests to changes in atmospheric CO2.

BIFoR FACE is a technological marvel. Built into existing woodland without the use of concrete foundations or guy ropes, the facility gently delivers its enriched-CO2 atmosphere to 30-metre patches of 160 year-old oaks, interspersed with hazels, sycamores, hawthorns, and holly.

Bluebells pop up every spring, badgers forage nightly for rich pickings of worms and grubs and tubers, and the birds sing unperturbed. Nestled throughout this bucolic idyll are scientific instruments, measuring everything from the greenness of the leaves to the wetness of the soil.

Now that the experiment has begun, we are expecting the impact of changing CO2 to show up in the leaf chemistry of exposed trees within days. A sugar pulse, labelled with the particular chemical signature of the dosing CO2 will then travel down the trees, appearing in the soil within weeks. Within three years, we predict that stem growth, canopy structure, and a host of other structural forest elements will be different in the patches exposed to elevated CO2.

Gradually the ‘push’ provided by the elevated CO2 will pass through all the checks and balances of a mature forest ecosystem, allowing, as each year passes, increasingly better estimates to be made of the land carbon sink in 2050 and the decades beyond.

Professor Rob MacKenzie

Director, Birmingham Institute of Forest Research
School of Geography, Earth and Environmental Sciences, University of Birmingham