Geoengineering Redux: Fertilizing Trees with Nitrogen to Fight Climate Change
by Jeremy Elton Jacquot, Los Angeles on 11.21.08
Image from Joshua Rappeneker
It's not quite ocean iron fertilization, but I have a feeling this new geoengineering proposed will still raise quite a few hackles. The idea, which originated with Federico Magnani of Italy's University of Bologna, is, as the name implies, fairly straightforward: You would fertilize, or "dope," as the New Scientist's Catherine Brahic put it, trees with nitrogen to stimulate their ability to absorb more carbon dioxide and, by increasing their albedo, to reflect more solar radiation back out into space.
More nitrogen: higher carbon uptake and higher solar energy reflection
In a new study published in the Proceedings of the National Academy of Sciences, Scott Ollinger of the University of New Hampshire and several colleagues discovered that forest canopies with higher concentrations of nitrogen tended to take up more carbon dioxide and reflect more solar energy than those with little of the nutrient.
Magnani, who has spent many years studying carbon uptake in nitrogen fertilized trees, reported similar results in a study he published 2 years ago in Global Change Biology. Beginning in 1994, he and his colleagues simulated chronic nitrogen deposition (deposition that typically occurs because of atmospheric pollution) by adding 3 grams of nitrogen per square meter to four different northern hardwood forests in Michigan every year.
Ten-year study showed chronic N deposition boosted ecosystem C storage
After a decade of observation, they concluded that, compared to a control treatment, nitrogen deposition had greatly increased ecosystem carbon storage (i.e. carbon sequestration) in both the trees and the surrounding soil. Magnani used the study's results to argue that a program of annual nitrogen fertilization in the northern hemisphere could potentially create a new sink for carbon dioxide.
Many scientists, including Ollinger, aren't sure this would be such a good idea. For one thing, little is still known about the relationship between albedo and nitrogen; even if the nutrient does act as a switch that changes the leaves' structure to increase their albedo, only certain species would be able to take advantage of this property. As a result, if we wanted to apply this method on a sufficiently large scale to effect carbon emissions, we would have to plant entire forests made just out of those few species.
And then there are all the environmental downsides associated with high nitrogen concentrations: nitrous oxide emissions (a far more potent greenhouse gas), groundwater contamination and drying (trees that consume larger amounts of nitrogen need more water), just to name a few.
For his part, Magnani agrees that more research needs to be done before governments or businesses can seriously consider spraying large swathes of forest with nitrogen. He has just submitted a research proposal to the European Union to study the long-term effects of fertilization on carbon storage -- specifically the effects of artificial fertilization. A side objective would be seeing whether it makes sense to plant northern forest species in regions where nitrogen pollution levels are already high.
But at what risk?
Like iron fertilization before it, I doubt this plan will win many converts outside of the scientific community. With the London Convention recently imposing restrictions on commercial fertilization, it remains to be seen whether the EU will be willing to support another risky geoengineering scheme.
More about geoengineering
Fake Plastic Trees to Solve Climate Change
This Month In Wired: Geoengineering and Ken Caldeira
Thirsty for more? Check out these related articles:
- Ocean Iron Fertilization Test in South Atlantic Given Go Ahead
- Sea Level Rise Predictions Too Low, No Abrupt Release of Methane: US Climate Change Science Program
- Incredible Edible Food Revolution is Happening
- Think Ocean Geo-Engineering is a Good Idea? Think Again, Australian Scientists Urge
I have trouble equating tree fertilization with ocean doping with iron. It may not be as desireable as organic farming, but much of the world routinely uses manufactured nitrogen on its agricultural crops.
Planting a diverse blend of trees on damaged land such as from strip mining or depleted agricultural lands and using low intensity fertilizer to sustain and accelerate growth strikes me as ecologically sound.
More research on the idea sounds good to me.
As pointed out, there are possible downsides to nitrogen supplementation of forests, but we may well need to institute a forest fast growth program the not too distant future if CO2 levels aren't controlled by other means. Knowing more about the subject would be a good idea. DB
Use of industrially-derived sources of N, like we slather on cornfields, is likely to have a very poor return on investment. Only Big Agra will benefit.
There are some ground-cover legumes, such as the vetches, that might actually do more good than harm. Let's look at them first.
First, nitrogen, N2, is a triple-bonded element. Breaking that triple bond requires a lot of energy. Let's look at the thermodynamics of this proposal.
Second, let's realize that humans have already radically altered the global nitrogen cycle with the Haber-Bosch process and artificial nitrogen deposition is already widespread.
Third, aquatic ecosystems would likely suffer under a widespread forest fertilization scheme.