Dam good nat­u­ral process of emis­sions

Tasmanian Country - - OPINION -

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.

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