Bru Pearce Blogs
There is a lot of talk about loss of biodiversity but very little is said about the loss of total biomass. A huge amount of evidence exists to show that the overall biomass on land has been massively reduced over the past 3,000 years and increasingly evidence is coming to light in respect of the loss of biomass in the oceans. Loss of biomass on land may well be as great as 50%, loss of biomass in the seas could be as high as 80%. If this is correct one of the consequences of man’s actions over the past 3,000 years is that the overall annual living carbon cycle has been massively reduced by perhaps as much as 70% of what it would have been over the preceding four million years.
I would argue that with a much greater carbon cycle the biospheres resilience would have been far greater than it is now in respect of maintaining atmospheric balance through major shocks, be they geological, biological or asteroid strikes. This reduced resilience is probably going to be reflected in the earth system sensitivity and suggest therefore that even David Wasdell’s figure of 7.8°C to doubling of atmospheric CO2 may be an understatement!
Evidence for the loss of biomass on land is all around us, consider the amount of land converted to agricultural use that had formerly been forested and further consider that the soils associated with an agricultural use, contain massively less organic carbon than mature forest soils. Into this equation one can also add the known areas of expanding deserts and growing urban expansion.
Evidence of the loss of biomass in the oceans is less well researched or understood. What is clear is that in the coastal environments around the world man has eradicated huge amounts of the shellfish, massively damaged reefs and we have data that shows a near collapse of the ocean fish stocks, but the baseline for the fish stocks is only 50 years old. If we look back 350 years when the world’s whale population had not been reduced by at least 97% and consider that then there would been an active nutrient cycle across most of the world oceans, then it follows that phytoplankton numbers would have been massively higher providing vastly more available food for zooplankton and the tropic pyramid above them. So that the entire oceans would have been teeming with life instead of having large areas as virtual lifeless desert.
The total amount of carbon in living biomass now is thought to be between 750 and 1,500 gigatons and I’m speculating therefore that 3,000 years ago it is likely to have been between at least 1,500 and 3,000 gigatons.
Using the low numbers this suggests that with good husbandry of our planet we should be able to grow and maintain in seasonal and hemispherical balance at least 750 gigatons of additional organic carbon.
Now our principal problem is are:
- That we have added in excess of 250 gigatons of carbon to the atmosphere about half of which has dissolved into the oceans and which will in all likelihood off-gas back to the atmosphere if atmospheric CO2 concentrations are reduced.
- And over the years since the start of the Industrial Revolution, and particularly over the past 30 to 40 years when atmospheric CO2 levels have been very much higher, huge amounts of radiant heat have been able to penetrate deep into the Earth’s oceans and this store of heat needs to be radiated back out into space.
To deal with this there is much discussion about preserving and expanding Arctic sea ice, cloud shields, and ocean brightening to reflect away radiation, but in the end the only real solution would be an overall reduction in greenhouse gases to a level a little below that of the 280 ppm experienced throughout most of the Holocene. Once the excess ocean heat has been radiated away the level could then be allowed to rise again to ensure proper temperature balance of the biosphere and as necessary to correct against the natural trend for us to dip towards the next ice age.
Usually when we speak of atmospheric CO2 reduction we are considering permanent sequestration of atmospheric carbon and we look to the natural annual sink that takes place due to biological activity as carbon transfers out of the living carbon cycle. It’s only in the case of reforestation that we really look to atmospheric carbon reduction due to increased biomass.
However where I see a real solution to our problems is in a big jump to a much greater amount of living carbon, drawing down say 325 gigatons of atmospheric carbon into an increased biomass, which I believe could be done in a matter of 10 to 15 years by growing forests, restoring soils and most importantly fertilising the oceans in such a way that the correct amount of nutrients are permanently available long enough for the re-establishment of the original ocean ecosystems.
Importantly the numbers show that this over correction would allow us some hydrocarbon burning leeway in order to make the transition and to maintain essential economic services. This is immensely important because as well as having significant greenhouse gases we also have atmospheric pollutants which shield us from solar radiation and if we fail to maintain these before atmospheric carbon levels are rebalanced then we risk an almost immediate temperature spike of another degree centigrade. The economic collapse which would come about if we stopped flying and reduced our hydrocarbon burning too fast, must be avoided at all costs, as it would immediately kick off a series of extremely severe positive feedbacks.
So we need a plan to commence biomass growth across the globe immediately and for a graduated reduction in hydrocarbon burning until we reach a sustainable level. In practice this means a rapid implementation of all renewable energy types and a complete retooling of our energy infrastructure. Hydrocarbon use needs to be prioritised so that is only used were it cannot easily be replaced by non-hydrocarbon energy systems.
Climate change is everybody’s problem, all 7.3 billion of us, and I argue that if we all get engaged either physically or by paying for it, in growing biomass, then we have a mechanism with the power and capacity to solve the problem. This is not a geoengineering proposal it’s a call for a Global Environmental Restoration Project and correct management of our only home.
13 July 2015