By Clare Ziegler, Rosemary Dyson, and Iain Johnston

Carbon dioxide is changing the world, and levels are continually rising. Human activities are pumping CO₂ into the atmosphere. This is affecting the climate and plant growth around the world. There’s an urgent need to know the effect of elevated CO₂ on the world’s ecosystems, in order to make accurate scientific, environmental, and economic predictions of future climate change.

Plants play a central role in the planet’s CO₂ budget. Photosynthesis takes in CO₂ from the atmosphere, and plant respiration releases it back. If more is taken in than is released, plants can act as a carbon sink and reduce atmospheric levels of CO₂. But how much of a sink can plants provide? And how will a changing climate influence this? Changing CO₂ levels affect how plants grow. Different plants may respond differently to changing CO₂. Other processes in an ecosystem may take up or release carbon. Because of these complications, researchers find it challenging to measure how much carbon is taken up by real ecosystems, like UK forests. In particular, we don’t know how future increases of CO₂ will affect forest ecosystems.