Dam good natural process of emissions
I write about the article (Tasmanian Country, November 23) about gas emissions from farm dams. The author, a PhD student from Deakin University, says dams make disproportionate contributions to emissions from aquatic microbes.
There is no doubt many of these dams are very complex ecosystems with all sorts of biological processes going and of course that means gases are being produced as microbes break down plant material.
Let’s concentrate on carbon, understanding that the big picture is more complex. The carbon that goes out of the dam has to come in first or the system would wind down to a lifeless state. What we have here is anything but lifeless. That carbon can come in from two sources, nutrient inflow with organic matter included or plant life in the dam photosynthesising and building new plants.
It hardly needs stating the carbon used to build the plants comes from the same atmosphere where the gases end up – the point being neither the dams or the lifeforms in them are creating carbon, no living thing does that. The biological processes in dams are just good at recycling carbon.
We have the contention this is a problem needing government help for farmers to make it go away, principally by reducing nutrient inflow.
There may be good reason to reduce nutrient inflow. The problem is doing that while letting water in at the same time.
We don’t have to worry about making any real net contribution to greenhouse gas emissions. Carbon out equals carbon in, or in fact there is probably a small increase in biomass over time.
This is certainly the case on the planet as a whole, where the biosphere is on balance sequestering about half the carbon emitted from fossil fuels.