Wet­lands are car­bon cap­ture kings

Sixty years ago when hun­ters banded to­gether to save wet­land habi­tats, they couldn’t have fore­seen just how valu­able their ef­forts would be.

Field and Game - - CARBON KINGS -

Field & Game Aus­tralia (FGA) emerged in re­sponse to con­cerns about the fu­ture of the iconic Pa­cific black duck and brought hun­ters to­gether to save the wet­land habi­tats cru­cial to a healthy pop­u­la­tion.

Hun­ters vol­un­teered to pay li­cence fees to fund the cre­ation of the net­work of State Game Re­serves, which con­tinue to pro­vide im­por­tant habi­tat for not only ducks but all water­birds.

Ac­cord­ing to re­searchers from the Deakin Univer­sity School of Life and En­vi­ron­men­tal Sciences’ Blue Car­bon Lab, Vic­to­ria’s wet­lands pro­vide an­other sub­stan­tial ben­e­fit, lock­ing away the an­nual emis­sions of 185 000 peo­ple, or roughly the pop­u­la­tion of Gee­long.

The tally, which came to 3 mil­lion tons of CO2 each year, in­creases our un­der­stand­ing of how the en­vi­ron­ment helps to reg­u­late green­house gas emis­sions.

Lead re­searcher Dr Paul Car­nell said in­land or non-tidal wet­lands were an in­te­gral part of Aus­tralia’s car­bon bud­get.

“While a lot more is known about how trees suck up and store car­bon, fresh­wa­ter wet­lands can ac­tu­ally se­quester 20 to 40 times more car­bon than forests on dry land,” he said.

The key to wet­lands’ success in car­bon stor­age is the mix­ture of plant material and sed­i­ment in the soil, which con­tains lit­tle oxy­gen, and makes it hard for the car­bon to be bro­ken down and re-re­leased into the at­mos­phere.

“In­stead the car­bon in this material is stored in the ground, that’s called car­bon se­ques­tra­tion, and each year new material is added to the wet­land’s over­all car­bon store,” Dr Car­nell said.

“It’s the re­verse process of dig­ging up and burn­ing coal or oil, here wet­lands are tak­ing that gas and putting it back into the ground.”

Vic­to­ria has about 530 000 ha of in­land wet­lands, which in­clude marshes, peat­lands, pools and lakes, mak­ing up about 2.33 per cent of the state’s land area.

As part of their study, which was funded by the De­part­ment of En­vi­ron­ment, Land, Wa­ter and Plan­ning, ecol­o­gists from the Blue Car­bon Lab worked with Vic­to­ria’s 10 Catch­ment Man­age­ment Au­thor­i­ties to take soil sam­ples from more than 100 dif­fer­ent wet­lands across the state.

The soil was taken to a lab where it was dried, pul­verised and put through a ma­chine to an­a­lyse how much car­bon it con­tained.

In to­tal, the re­searchers es­ti­mated Vic­to­ria’s in­land wet­lands had a soil car­bon stock of 68 mil­lion tons, worth about $6 bil­lion under Aus­tralia’s most re­cent car­bon price.

The study, pub­lished in the jour­nal Global Change Bi­ol­ogy, found Vic­to­ria’s alpine wet­lands had the high­est over­all car­bon stocks, while per­ma­nent fresh­wa­ter sites like bil­l­abongs se­questered the most amount of car­bon each year.

“Many of us al­ready know that wet­lands are great places to find birds, are im­por­tant for fish­eries and pro­vide vi­tal ecosys­tem ser­vices such as nutrient cycling, ero­sion con­trol and flood mit­i­ga­tion. So this data shows they play a crit­i­cal role in car­bon stor­age too,” Dr Car­nell said.

“On the flip side, this means dis­tur­bance and loss of wet­lands has the po­ten­tial to re­lease sig­nif­i­cant quan­ti­ties of CO2 back into the en­vi­ron­ment.”

Head of the Blue Car­bon Lab, As­so­ciate Pro­fes­sor Peter Macreadie said the new study es­ti­mated that since Euro­pean set­tle­ment, the loss of wet­lands in Vic­to­ria had re­leased up to 74 mil­lion tonnes of CO2 equiv­a­lents, equal to the emis­sions of 16 mil­lion cars over one year.

“Since Euro­pean set­tle­ment we have lost more than a quar­ter of our non-tidal wet­lands here in Vic­to­ria, mostly due to agri­cul­tural prac­tices and de­vel­op­ment,” he said.

How­ever, wet­lands also have a dark side which off­sets their cap­ture and stor­age of car­bon.

“These wet­lands can be large sources of meth­ane emis­sions. They’re ef­fec­tively na­ture’s fart fac­to­ries. So that’s some­thing we’d like to be able to quan­tify fur­ther in fu­ture re­search too.”

In the mean­time, As­so­ciate Pro­fes­sor Macreadie said it was crit­i­cal Vic­to­ria prop­erly pro­tected and man­aged the in­land wet­lands it had left in­clud­ing us­ing an ex­ist­ing path­way, money col­lected through car­bon off­sets.

“Right now, if you pur­chase a car­bon off­set for your flight to Syd­ney for ex­am­ple, that pro­gram will most likely plant a cer­tain num­ber of trees they es­ti­mate will grow to store the CO2 equiv­a­lent to your plane trip,” he said.

“But we know that wet­lands are far more ef­fi­cient at stor­ing car­bon than trees. Here in the Blue Car­bon Lab, we’re col­lect­ing the in­for­ma­tion so that gov­ern­ments and car­bon off­set providers may one day be able to off­set car­bon emis­sions by restor­ing wet­lands.“

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