Garden Ponds Combat Climate Change

Kat - We all know that trees can take up carbon from the atmosphere, helping to combat climate change.  But there's another important place where carbon is taken up that you won't find on most diagrams of the carbon cycle.  That's ponds.  I caught up with John Downing, professor of ecology at Iowa State University who has just published results suggesting that ponds could play a vital role in damping down the greenhouse effect.  I started by asking him what his results show.

John - Actually it's one of the smallest aquatic systems and the most carbon-active in the biosphere and are probably absorbing as much carbon as the global oceans.

Kat - How did you find this out, that they capture so much carbon?

John - We measured the deposits of carbon and how thick they were and various sediments.  We also measured their rate of deposition in little constructed system across the central part of the United States.

Kat - What sort of ponds are these?

John - Farm ponds.  Yeah, there are 76,000 square kilometres of farm ponds in the world and they're burying carbon at about 2kg per square metre per year which is a tremendous amount of carbon because they're so active even though they're small.  They're disproportionately important to the global carbon cycle.

Kat - So what does this mean, for example here in the UK?  Should we all be going out digging ponds?

John - It's not a bad idea really!  They are also very nice for recreation, marvellous for biodiversity.  We are encouraging people in the United States to build more ponds.  They trap a tremendous amount of carbon and in some areas of the world we've taken away a lot of these ponds.  We've filled them in, we've destroyed them, we've drained them on purpose, put them back.  We're going to actually be able to have a positive effect on the amount of greenhouse gas that goes into the atmosphere.

Kat - So we should be digging ponds rather than planting trees?

John - I didn't say rather than, I said build ponds and then plant trees around them.  They're both good things to do.

Kat - Professor Downing's research only relates to ponds in the US.  What about the situation in the UK?  I spoke to Jeremy Biggs from the charity Pond Conservation to find out what the situation might be like over here, across the pond.

Jeremy - Well, we've just done some preliminary research looking at the effects of ponds in trapping carbon.  What we found so far is that they seem to be as good as John is suggesting over here as well.  We've done some very preliminary survey so far in the last couple of months or so.  We're capturing carbon at just about the same rate as he is in America.  That's a pretty exciting result for us because it suggests that they might work as a carbon capture technique over here as well.

Kat - What does this mean for conservation policy and for climate change policy?

Jeremy - Well, it suggests that there's another way of mitigating the impacts of climate change by capturing carbon, taking it up in ponds (if we make ponds of the right size and shape and put them in the right places) then we should have another method for trapping carbon just as we do with trees at the moment.  If we do both these things we will actually trap more carbon from the atmosphere and hope to mitigate some of the effects of climate change.