I’ve
arrived at the first stop on my quest, Eazrah’s nearest galactic neighbour,
Planet Crooter.
I was
greeted warmly by the inhabitants here and have spent a few days speaking with
them about the current state of both our planets' climates, and what action is
being taken to control them. They told me about a form of geoengineering
here called iron fertilization, though many inhabitants claim it is not really
geoengineering at all. I’ll explain why later on.
This is
the idea:
1. Iron powder is dissolved into the oceans
(The
focus is kept on regions of “high-nutrient, low-chlorophyll” (HNLC) surface
water. HNLC means there are lots of nutrients necessary for life in the water,
but there’s not much chlorophyll – a pigment crucial for phytoplankton and
algae to photosynthesize – indicating there’s not much photosynthesis or plant
growth going on. As the water is rich in other nutrients, it’s thought that
iron (of lack thereof) limits phytoplankton growth.)
2. Influx of iron into the water stimulates tiny
organisms – phytoplankton and algae – to grow into colonies (they call it a plankton bloom,
see figure 1)
3. The growth of these organisms effectively sucks
organic carbon out of the water...
4. ... meaning less carbon can travel from the
water back into the atmosphere. There's also a greater capacity for carbon
dioxide to dissolve into the ocean from the atmosphere
5. When the phytoplankton and algae die they sink to
the ocean floor, trapping carbon on the ocean bed. This part is the carbon
sequestration
Figure 1. The natural-coloured top image is a spectacular plankton bloom off Kamchatka. The bottom image shows scientist-estimations of chlorophyll concentrations in this area. Regions of high chlorophyll concentration correspond with densely plankton-populated water. (Images by Robert Simmon and Jesse Allen, based on MODIS data, via NASA) |
I'll explain a little more...
Some scientists speculated that a lack of
iron was limiting biological activity in HNLC regions. In an early experiment Coale et. al. (1996) tested this out in
a HNLC part of the Pacific Ocean. They saw that when iron was dissolved into
the water, algae and phytoplankton populations did indeed start to grow. They
also saw a significant drawdown of carbon from the surface water, suggesting iron
fertilization had potential as a method of carbon sequestration.
Boyd et. al.
(2000) then tested out the same
thing in the Southern Ocean. They saw that although there was some increase in
algae and phytoplankton, they couldn’t prove there was much carbon
sequestration occurring. But then in 2009, Pollard et. al. (amongst
others) did confirm carbon sequestration as a result
of (natural) iron fertilization in the Southern Ocean.
Mixed results really: it seemed like iron
fertilization did stimulate plankton growth, but it was unclear whether it
would lead to significant carbon sequestration.
Then came the largest-scale “experiment”
of iron fertilization. But it wasn’t performed out of scientific endeavour. A
businessman, set on earning money from carbon credits, convinced a
small marine restoration organisation, Haida Salmon
Restoration Corporation (HSRC), to release 100 tonnes of iron sulphate
into the north-eastern Pacific Ocean to boost salmon populations. (The idea
being that a plankton bloom would boost fish populations, including salmon.)
In terms of salmon, the “experiment” was a success. But from a geoengineering
perspective, it seemed there was little carbon sequestration as most of
the phytoplankton were eaten by fish before they had a chance to die, sink to
the seafloor and lock carbon away.
The move was also controversial with
environmentalists here: there are plenty of reasons why anyone using iron to
artificially create plankton blooms should be careful. From risking depleting
surface-water oxygen, to accidentally encouraging toxic phytoplankton or algae
species blooming.
So far I'm not too impressed with iron
fertilization. The evidence suggesting it leads to carbon sequestration is
weak, but some evidence does exist so I think it deserves
more attention. Maybe the benefits of iron fertilization are more
significant over a longer time scale? I’ll stay on Planet Crooter a little
longer to find out.
Interesting post! Thanks! It does seem that the business man and HSRC acted rather irresponsibly! I hope there is adequate monitoring and enforcement of international and local environmental legislation in Eazrah, in case anything like that happens on your planet!
ReplyDeleteThanks, Geoff :) Very irresponsibly indeed. Iron fertilization is such a unpredictable technology and doesn't seem to be very effective at all, so hopefully we won't be seeing any more rogue "scientists" dumping tonnes of iron into the sea in its name.
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