During the last ice-ageA period of reduction in Earth’s temperature of between about 4–7 degrees that resulted in the rapid expansion of ice sheets and glaciation of much of the Earth’s surface. More 20,000 years ago, there was a particularly cold period. Scientists have thought this might have had to do with an influx of iron into the Southern Ocean. Biologically-available iron is really rare in the sea. When it’s added in quantity it supercharges algal photosynthesisMeaning how plants extract energy by absorbing water and using radiation from the Sun to combine it with carbon dioxide to create sugars. More leading to more carbon uptake and reduced atmospheric warming. But iron fertilisation without animals could spell disaster.
Fertilising the Southern Ocean
The paper titled “A circumpolar dust conveyor in the glacial Southern Ocean” just published in the journal Nature Communications [1] has discovered that dust from Central South America may have contributed 80% of the iron input during that period. Each of these findings shines a new spotlight on the subject of Iron fertilisation … the idea that we could artificially prime the Southern Ocean with dust, as a way to combat climate change.
Animal impactWhat is Animal Impact? Without wildlife, Earth would not be habitable for humans, because it's animals that stabilise ecosystems. It’s a fundamental law of nature that animals (and humans) exist because we are the most likely lifeforms to minimise environmental chaos. Animal impact, therefore, is a measure of how much all wildlife is collectively responsible for creating a habitable Earth. The More is not being considered. Without sufficient wildlife this end-of-pipe engineering solution could have equally negative consequences for human life support.
Ocean ecology was built on functional processes driven by animal communities over millions of years. The clinical precision by which animals deliver nutrientsEnergy and nutrients are the same thing. Plants capture energy from the Sun and store it in chemicals, via the process of photosynthesis. The excess greenery and waste that plants create, contain chemicals that animals can eat, in order to build their own bodies and reproduce. When a chemical is used this way, we call it a nutrient. As we More in time and space is part of a long-term lifecycle. If precision isn’t reached, the system doesn’t stabilise and the animals don’t survive. If the animals don’t survive, precision can’t be reached. The existence of animals is the mechanism for stability and human existence.
If precision isn’t reached, the system doesn’t stabilise and the animals don’t survive – and if the animals don’t survive, precision can’t be reached.
If we decide to do iron fertilisation in the absence of animal populations, our application will be nowhere near as precise as it needs to be, to avoid ecosystemHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More disfunction, which could lead to collapse of fisheries. As evidence of this, loss of global soil fertility is entirely down to the over-application of fertilisers on land. It’s the same process. Iron fertilisation and farm fertilisation are both adding energy to systems. Our imprecise application of fertiliser on land, already threatens world food security within a few decades.
Evidence from the past
20,000 years ago, when the Earth was subject to iron fertilisation from the continent, this was sufficient to alter the temperature of a whole planet. Speciation, the rate at which animals evolve, is fastest when temperatures are cold, which is why the prehistoric record shows massive increases in species richnessThe number of species within a given area. Note, this is often confused with biodiversity but is very different. Species richness is not equal in all areas. Desert species richness is lower but the scale and intensity of species function can still be significant as biodiversity is not about number of species, it's about ecosystem processes. More after ice-ages. During this last cold period, animal populations were able to adapt and rebalance the waste energy and bring Earth back to a temperature more suited for human life.
Wind forward to today, and we are in the midst of a mass extinctionAnimal life hasn't existed for very long on planet Earth. In the last 500 million years, there have been five mass extinctions, defined as events that wiped out at least 75% of animal life. The Devonian mass extinction is considered to have been caused by the rise of plants on land, which polluted the oceans in the absence of animals. More. We have lost 98.5% of the Blue Whales from the Antarctic, for example. These animals, among many others, are the mechanism that could allow us to subtly re-engineer systems, in the knowledge they provide a safety-net for our unsystematic approach–for that is all it can ever be. We can never precisely replicate ocean iron-cycles without animals to do that for us.
We’re talking about throwing massive amounts of free surplus energyThe energy of a system that is emitted as waste and is not part of ecosystem processes. There is always some free surplus energy as this creates the basis for evolution where new species exploit gaps in the ecosystem where free energy becomes available. Surplus energy can occur as a result of disruption or disturbance. When free surplus energy reaches More at enormously sensitive systems that drive a planet’s core functionality for human survival. Why would we imagine we could be any better at that, than we have been with fertilising the land?
The take home message
The take home message is simple. Before we even consider iron fertilisation, we need to make sure we’ve rebuilt and are maintaining wildlife population processes close to a natural state – that means having wildlife in the right proportions. Then we have to apply any efforts extremely carefully, if at all. Because rebuilding wildlife populations and stemming our use of fossil fuels might just be a savvier alternative.
- Struve, T., Pahnke, K., Lamy, F. et al. A circumpolar dust conveyor in the glacial Southern Ocean. Nat Commun 11, 5655 (2020). https://doi.org/10.1038/s41467-020-18858-y
- Deborah Pardo, Jaume Forcada, Andrew G. Wood, Geoff N. Tuck, Louise Ireland, Roger Pradel, John P. Croxall, Richard A. Phillips. Climate and fisheries drive albatrossShy Albatross are a signal of ocean health and breed on sub-Antarctic islands. Their population has halved in the last 35 years More declines. Proceedings of the National Academy of Sciences Dec 2017, 114 (50) E10829-E10837; DOI: 10.1073/pnas.1618819114
