Plants to the Rescue

Plants made our current atmosphere and plants can keep it balanced.

When plants first showed up on earth about 3.5 billion years ago, carbon dioxide made up more than 20% of the atmosphere. There was no significant oxygen in the air so none of us animals existed. Cyanobacteria and then plants used sunlight to extract carbon from the CO₂; in the process they released O₂ and we animals evolved and began to convert some of that O₂ back to CO₂. The influence of the plants has been much greater than our influence. Since humans have been around, the air has been about 20% O₂ and .04%CO₂.

The chart above is from newscientist.com. The numbers on it are largely observations as opposed to theory or “scientific consensus”. The UN report on climate cites these numbers as do many who feel the report overstates the dangers of climate change.

The green arrows show that in 1750 as the industrial age began, the amount of CO₂ in the atmosphere was about the same from year to year because the amount of that gas emitted by respiration, rotting, weathering of rock, and release from the sea was roughly balanced by the amounts of CO₂ recaptured by photosynthesis and ocean absorption.

As of 2004 human activity (see the red arrows) added 32 additional gigatons (a gigaton is a billion tons) of CO₂ each year to the emissions from 1750. Interestingly, plants have stepped up their activity by sequestering an additional 10 gigatons of CO₂ annually (remember CO₂ is fuel to them) while the ocean is also absorbing net 10 gigatons more as it stays in balance with the air above it. That still leaves an imbalance; and so in 2005 total CO₂ in the atmosphere was increasing by about 15 gigatons/year (the squiggle “~”  in front of “15” mean “about”)  . That number is probably about 18 gigatons/year now due to increased human activity.

Let’s assume we don’t want the composition of the atmosphere to keep changing because we’ve gotten used to things the way they are and let’s assume that we stabilize human emissions about where they are now or in a few years. All we need is for the plants to remove an additional 18 gigatons of CO₂/year and sequester it as carbon in the soil and we will have completely neutralized the human contribution. That’s not unreasonable to work towards since they are already processing more than 450 gigatons/year and since they are already increasing their production without any help from us. Since plants grow faster when they have more fuel, an additional upside of plants using our excess CO₂ is that the amount of food crops per acre will increase. Also soil with more carbon in it requires less irrigation and fertilization. What’s not to like?

Nevertheless, if we just wait for plants to evolve to establish a new equilibrium (which they always have done and will do eventually), we will be doing a pretty big science experiment with the effects of atmospheric CO₂ on climate. Last week I wrote about an initiative at the Salk Institute to develop Ideal Plants® which have woody roots that increase the amount of carbon left in the soil when the plant is harvested or dies. We can also speed up the evolution of plants adapted to the increases in atmospheric CO₂ which have occurred since 1750 and get these new plants disseminated; I’m sure there are people working on this.

We have made progress in reducing CO₂ emissions both by replacing coal with natural gas and by adding renewables to our energy mix. There is no reason why that progress should stop. Although the news is dominated by deforestation, developing countries are reforesting. The green hills of Vermont were denuded 100 years ago for sheep farming. As counties come out of poverty, which they are doing rapidly, they are probably not going to shun air condition, cars and meat; but they are likely to reforest when they don’t need to burn every scrap of wood for fuel. If we reforest with greener trees which store more carbon, all the better.

Joanne Chory is the leader of the Salk Institute Harnessing Plants Initiative. In a podcast, she says:

“… I have a wake-up call for anybody out there who thinks they’re working in an area related to climate change, but we have to also draw down some of the CO₂ we’ve already put up there, and the only way to do that, that I can see, is by capturing CO₂, and plants are going to do it way better than any machine. And people will say, ‘What can I do? Should I drive an electric car?’ Well you can drive an electric car, that’s a nice idea. But I can tell you this fact: if every car in the United States became an electric car today, it’s not making a global impact with the amount of CO₂ we put out. So you still have to just suck it out of there somehow, and the only way I can see of doing it is by having a number of different approaches that involve nature and humans acting together.”

See also:

The Ideal Green Solution

Undeserved (and Useless) Rebates I Got (about electric cars)

What Should We Do About the Threat of Climate Change?