 Methane. It's not a particularly glamorous greenhouse gas conjuring images of landfill, waste, sewage and cows. The truth is far, far more important. Methane is a very powerful greenhouse gas, about 25 times the heat trapping power of carbon dioxide. Wetlands are the largest source of this gas to the atmosphere. They act like the canary in the coal mine of the climate system. When the climate warms, the wetlands, which are highly sensitive to temperature and rainfall, respond rapidly, producing massive amounts of methane. Here at the Open University we're focused on understanding the processes of production and emission of methane from the largest individual source of this gas, wetlands. We discovered that trees, which occupy 60% of Earth's wetlands, channel methane formed deep within those soggy soils out to the atmosphere. So to make a measurement of methane that's coming from tree stems, we attach a chamber to the side of the tree, and this is connected to a methane analyzer, a laser-based analyzer, via these tubes. And the concentration of methane is recorded on this instrument here. We know that the roots of trees need oxygen to survive, but in these soils they're completely depleted of oxygen. So trees have developed a mechanism by which they can get oxygen down to their roots. They have these hollow tubes within the tree stems that are linked down to the roots. Now this allows oxygen in the atmosphere to get down to the roots where it can enable them to respire. In these soils there's plenty of methane being produced, and this methane can come out in the other direction, out to the atmosphere. In the few ecosystems we have studied in detail, in Panama and the Amazon, methane is pouring out of the trees. And in the threatened peat swamp forests of Borneo, trees are the largest individual source of methane to the atmosphere, far larger than the soils which have been studied for decades. This of course doesn't mean we should be cutting down trees. Wet forests have been emitting methane throughout history. What's more important is tackling human emissions as landfills, cows, and leaky natural gas pipelines. But now, thanks to our research, we have a much better understanding of how these wetland ecosystems function with respect to the methane cycle. This is crucial as without a detailed understanding of the function of wetland forested ecosystems in the methane cycle, we risk underestimating their contribution to Earth's climate, and it also makes it extremely difficult to predict their response to future climate change.