Oceanic iron fertilization: A technofix or a green solution?

Most efforts to address climate change so far have aimed to reduce our carbon dioxide emissions. Unfortunately, these efforts haven’t had the effect that people had hoped for. Emissions appear unlikely to decline anytime soon, due to the rapid economic growth of developing countries. Carbon capture and sequestration turned out to be more difficult than people had assumed, as most of these experiments have been cancelled.

It would have been possible decades ago to come to an agreement on the need to end economic growth and reduce our overall energy use and material consumption. As Tim Jackson has shown, nine billion people by 2050 with the standard of living currently enjoyed in the EU would have to emit CO2 at less than 2% per dollar of GDP of our current level, something that seems very implausible.

The focus thus began to lie on looking for new technologies, that would allow us to continue to pursue growth without suffering the consequences of climate change. As John Michael Greer has pointed out however, there is no rational reason whatsoever to assume that there has to be some source of energy out there that will have all the same advantages as fossil fuels, but without the catastrophic effects on our biosphere.

To assume that we can simply move on to another source of energy without suffering any disruption to our standard of living reveals an anthropocentric cognitive bias. As we have found out in the years behind us, there are limits to the degree of power that technology can give us over our natural environment. The power technology has granted us has also led us to develop a blind spot in our recognition of the degree to which we are dependent on the functioning of our ecosystems.

Of course, when we discover that we fail to reduce our fossil fuel use, there are also other options available to us. The other side of the equation, carbon sequestration by the biosphere, is not fixed in place but dependent on a variety of factors that include human land use.

One option available to us is known as oceanic iron fertilization. In large parts of the ocean, iron is thought to be the limiting element in carbon sequestration by algae. Under iron deficient conditions, every atom of iron can be used by algae to sequester 106,000 atoms of carbon. As a consequence, iron fertilization theoretically allows us to sequester a lot of carbon dioxide, at very low costs. In practice results have been somewhat disappointing however. Sequestering 1000 ton of carbon requires a single ton of iron.

Of course, there are a lot of reasons to be skeptical and worried about the potential impact that such interventions can have. We are after all intervening in a complex system, which have a tendency to react in ways that are difficult to anticipate in advance. Even experiments done on a limited scale may not adequately translate into the large scale projects that would help us to cope with climate change.

Fortunately, we can observe what happens when oceanic iron fertilization occurs through natural processes. Volcanic eruptions fertilize the ocean with iron from their dust at a very large scale, at seemingly random intervals. The ecological harm done by such fertilization seems to be very limited.

The argument, that iron fertilization represents an intervention in the ecosystem, can also be turned around, to argue instead that iron fertilization fills a hole in the ecosystem, left by human activity. The rate at which carbon dioxide enters our atmosphere is extremely rapid, we know of no geological analogue. As a consequence, certain slow negative feedback processes take a long time to become relevant and prevent escalating temperatures.

As an example, a gradual increase in temperatures is normally associated with an increase in icebergs that travel across the ocean and deposit nutrients in the ocean, including iron. This process is thought to sequester a significant share of the carbon dioxide in the atmosphere. Because our carbon emissions are now so abnormally rapid, oceanic iron fertilization could be interpreted as an attempt to substitute for the natural negative feedback that takes time to emerge, until it has time to kick in.

In addition, there is another problem that humans have caused, in which oceanic iron fertilization can play an important role. The decline in whales has likely led to a decline in algae. The whales defecate and dive to deep depths, continually circling iron throughout the ocean, sequestering large amounts of carbon dioxide in the process and helping to keep the oceans they inhabit full of life. The decimation of whales in recent centuries has reduced the cycling of iron.

For humans to add iron to the oceans could thus be seen as performing a compensatory role that whales can not currently adequately perform due to their low numbers. An increase in algae due to iron fertilization may have the effect of increasing whale numbers. For this reason, studies that find that the sequester carbon dioxide does not sink to the bottom of the ocean, are not per definition failure, if it means that the nutrients continue to be recycled throughout the food chain.

Estimates of the role that iron fertilization can play reveal a limited impact. One estimate, where iron limitations in the ocean are eliminted globally, calculates that 33 parts per million could be shaved off our atmospheric CO2 levels by 2100. This however, is an underestimate of the full impact that fertilization can have.

Life creates the conditions that allow more life to come into existence, algae are perhaps a prime example of this rule. Algae blooms are brightly colored, increasing the planet’s albedo. An example of such an algae bloom is shown below:


This example in particular is a coccolithophore bloom, which are becoming increasingly common due to our changing climate. The bright color increases the planet’s albedo, thus reducing global temperatures by reflecting more sunlight. In addition to this, algae produce large amounts of dimethylsulfide, which increases the generation of clouds, reflecting more sunlight and further aiding in the stabilization of global temperatures. The total potential effect on global temperatures is thus likely to be much larger than hitherto estimated based on sequestered carbon dioxide alone.

It seems to me that the top priority for environmentalists should currently be to preserve a habitable Earth for as many species as possible. Oceanic iron fertilization can play a role in this, as it fills a gap created by human interventions in natural processes. It does not have the potential to avert a catastrophe on its own, but it should not be dismissed as part of a broader plan when combined with other options that will hopefully allow us to avoid a global catastrophe as our fossil fuel use continues unabated.


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