Comment: boosting plankton is messing with a system we don’t understand

The Times
January 29, 2009
Frank Pope, Oceans Correspondent

The transformation of huge tracts of open ocean from lifeless blue deserts to carbon dioxide-hungry blooms of green organic growth should bring joy to the hearts of environmentalists. Instead, the prospect of large-scale iron fertilisation is met only by their panicked cries of alarm.
Those in favour of iron fertilisation say that half of our planet’s carbon dioxide is already absorbed by phytoplankton blooms. Why not just add a little iron to increase the uptake? It is, after all, a natural process.
The theory of how the artificial addition of iron — essential for phytoplankton growth but often lacking in the open ocean — can help to fight climate change is simple. The iron dust sparks a vast bloom of phytoplankton, locking up large amounts of carbon dioxide in their bodies. When the plankton die some sink to the seabed, along with their carbon, to become the future’s fossil fuel.
Natural systems are never so simple, however, and each stage comes with a range of variables that has geo-engineers quibbling over economic viability. Their complexity belies another problem: we’re messing with a system we don’t understand.

Even the physics of the weather escapes our detailed understanding, and reflecting sunlight with giant mirrors or seeded clouds may cause unintended consequences. Tinkering with biology, however, brings with it an entirely different level of complexity.Phytoplankton are not just any form of biology either. They make up the planet’s biggest biomass and are at the base of most marine food webs. Previous experiments show that fertilisation appears to alter the species composition of plankton communities, favouring larger species over small.
It’s tempting to think changes on this scale would make no difference, but microscopic animals that eat small species can’t eat the big ones, and the effects cascade upwards through food webs. Because of phytoplankton’s position at the very base of marine life, changes to their population dynamics and diversity could easily upset the balance of entire ecosystems.
Opponents of iron fertilisation say that climate change is only one of the problems we face.
The effects of plummeting biodiversity are harder to predict financially and so receive less attention, but ecosystems and the diversity of life they contain are just as important when it comes to making the planet habitable for the likes of us. To environmentalists, life in the sea is already on a knife edge. Endangering the resilience of these systems in an effort to reduce atmospheric carbon dioxide is like swerving away from a six-headed monster only to end up heading for a whirlpool.