As the COP negotiations increasingly look to agriculture, forestry, and other land uses as tools to mitigate and adapt to a changing climate, methanogenesis – the biological production of methane by single-celled organisms – must be taken into account. This methane production is very similar to fermentation, the process used to produce alcohol. In fermentation, when yeast is denied access to oxygen, the yeast produces alcohol as a waste product. Humans do this too when exercising, producing lactic acid (this is why your muscles burn when you are out of breath). In methanogenesis, when a certain type of bacteria is denied access to oxygen, the bacteria will produce methane as a waste product.
This is a serious concern to land use managers. Rice production is one of the largest human sources of methane because of the low-oxygen content of the water in submerged rice paddies. To make matters worse, as the climate warms the bacteria in rice paddies produce higher levels of methane.
Another land use concern is the construction of hydroelectric dams. Hydroelectric dams are often viewed as a viable renewable energy alternative to fossil fuels, but because of the low-oxygen content of the water of the reservoir, organic material that gets caught at the dam decomposes to produce methane. Some even argue that hydroelectric dams are a net cause, not a solution to, climate change.
On top of all this, a recent study discovered a new methane-producing group of organisms that live in wetlands, lake and river estuary sediments, mud volcanoes, and deep-sea vents. This discovery revealed that humans still have much to learn about the carbon cycle. And this is not to mention all of the other sources of methane, both human (e.g. energy and waste production, livestock) and natural (e.g. wetlands, oceans, termites).
Fortunately, there are ways to manage these concerns. Rice paddies can be drained mid-season to kill off the methane-producers, and alternative fertilizers have been shown to reduce methane emissions. Hydroelectric dams can be managed to reduce organic matter in reservoirs, both by harvesting trees and other plant matter before the reservoir is flooded and by capturing organic matter farther upstream before it reaches the reservoir. Finally, researchers have also discovered methane-consuming bacteria that could play an important role in the reduction of methane emissions. Land use managers must consider these methane-control techniques as we move to address climate change.