Defining
"Unacceptable Environmental Change":
A Closer Look at the
Problem of Nitrogen use
So, really, where
shall we begin? There seems to be too many problems we should address in the
environment. Rockstrom et al.'s highly-embraced (but perhaps oversimplified) concept of 'Planetary boundaries'
tells us that when these boundaries are crossed planet earth will enter a
completely unknown (and hence distressing) change of state. From this diagram
,we observe our most pressing concerns-
biodiversity loss, and nitrogen use and climate change. This post addresses our
use of nitrogen which has very, very strong links to agriculture.
(The black line shows
the "safe operating boundaries of our planet")
Synthetic fertilizers- the problem!
It is quite
mindboggling to know that currently,
anthropogenic nitrogen fixation exceeds that of all
natural processes combined.
Essentially agriculture has been the consuming the bulk of it. The sharp
rises in crops yields over the past decades basically correspond well to the
amount of nitrogen used.
For a long time
(before modern agriculture) farmers had the practice of restoring vigour to the
soil by using bones with the use of H2SO4 (sulphuric acid) to digest these
bones. Investigations by Justus von Liebig showed that Nitrogen was the key
part of amino acids and nucleic acids ( the building blocks of cells). And
later he invented the Haber process which converts atmospheric nitrogen into a
form usable by plants (N2 → NH3 → Nitrates). Lawes then patented and
commercialized the processes, making high amounts of artificial nitrates easily
and cheaply available.
The acceleration in
nitrogen use was fuelled further by the green revolution. The green revolution
was characterized by genetically modifying dominant food crops (e.g. rice,
wheat) that increased the grain (edible) production of a plant and decreased
straw (inedible) growth. However, the viability of these high yielding
varieties was conditional. It depended on higher levels of water and
fertilizer. This resulted (alongside the provision of government subsidies) in
excessive levels of nitrogen such that
there was a 800% increase in fertilizer per hectare in places like Latin
America.
This uninhibited use of fertilizers are not
without their drawbacks:
Degradation of ecosystems
Firstly, pollution.
Agricultural run-off results in excessive amounts of these fertilizers entering
aquatic ecosystems such that eutrophication occurs. This destabilizes the
system and wipes out ecosystem services they provide e.g. clean water,
biodiversity etc. Unfortunately this is a world-wide phenomenon that is very
prevelant.
Health Effects
Secondly, the
effects on health pose as an occupational hazard to farmers and the general
public. Nitrates that seep into ground water end up in drinking water supplies.
When in the body, they are converted to nitrites by bacteria which alters
haemoglobin resulting in sicknesses like the Blue Baby Syndrome. Also, acidic
juices in stomach convert them into nitrosamines which increase the risk of
cancer.
Climate Change
Like most other
things, the widespread proliferation of synthetic fertilizers was due to the
cheap availability of energy (fossil fuels) to enabled the Haber process. It
was concluded by Pimentel in 1974 that to feed entire world with the modern
agricultural US system, agriculture would account for 80% of our energy use. An
excess of converted atmospheric nitrogen in our atmosphere also gives rise to
an increase in greenhouse gas emissions in the form of N2O (from livestock and
soil emissions) - a very potent greenhouse gas (300 times more than CO2). In
fact, agriculture contributes to more than 1/2 of the anthropogenic emissions
of N2O.
Synthetic fertilzers- a problem?
Energy Use
In a helpful review
by Jeremy Woodes et. al. (2010), they emphasize the
utter reliance of modern agriculture on fossil fuels today. However, fossil
fuel inputs including that caused by fertilizer manufacture have yielded
positive energy ratios (i.e. energy out put > energy input). Therefore, from
this point of view, one can say that synthetic fertilizers are indeed an
efficient use of resources. It has also been shown that while agricultural
energy use is growing due to increasing food production, it is not like
Pimentel predicted "80% of our energy use". Instead, it only accounts
about 3% of total consumption today. Technological improvements have definitely
contributed to this efficiency (although of course one must take into account
the overall increase in energy use).
Reduction in Global use?
Rockstrom et al.
(2009) propose the
boundary to be "limiting agricultural and industrial nitrogen fixation to
35 x 109 kg/year". As an attempt to view this diagram with some caution, I
went about researching on the exact problems of nitrogen.
Blomqvist et al.(2012) argues that there is
little evidence supporting the notion that there will be negative effect on
humans when we transgress these 'boundaries' and that there are "no global
tipping points beyond which ecological processes will begin to function in fundamentally
different ways" in regard to 6 of the 9 boundaries (biodiversity loss,
nitrogen levels, freshwater use, aerosol loading and chemical pollution)
With regard to
nitrogen, he argues that while there are excesses in synthetic nitrogen and the
problems of pollution etc. will be relevant, there are also areas (e.g. in
Africa) where the soil is depleted of its nutrients and some synthetic
fertilizer would help restore the arability of the land. Hence, global limits
make no practical sense when nitrogen use is vastly different in various
localities. Another point of contention he puts forth is that there is no
evidence that excessive inputs of nitrogen level will destabilize human
development. Instead, he proposes a view of our environment that allows us to
"identify and explicate trade-offs".
In response to these misgivings, Rockstrom et al qualified heir concept. As
with many popularizations, concepts get generalized and oversimplified.
Firstly, they contend that many of these boundaries act as "slow
variables". These variables, though they have not shown be direct causes
of drastic change, "act as buffers" which enhance the resilience of
the system.
Secondly, they had
never claimed that the evidence supported 'planetary tipping points' but
instead the evidence has shown that local and regional scaled tipping points do
occur worldwide (cumulative change) hence giving them the title of a 'major
global concern'. Tipping points exist in systems like the lake ecosystem
whereby there exists multiple stable states in ecosystems. In lakes, when
excessive nutrient (like N, P) inputs along with other triggers encourage the
ball to suddenly tip over a healthy
state to another state (which Rockstrom argues as undesirable). To revert from
that state would require even larger restorative strategies as compared to a
linear system. In other words, we will then be "locked-in".
Conclusion:
The key word in this
debate is "global". Calls
for reductions in nitrogen everywhere i.e. globally are unsupported but
misuses, i.e. both too little and too much, are likely to be extremely
prevalent and still warrant a global call for concern. This call for concern,
in my opinion, should not then be one that single-mindedly calls for a
reduction in nitrogen use but rather an informed choice of nitrogen input based
on the ecological settings. Nevertheless, it is true that, as seen by the
enormous read flare on the diagram and with the knowledge of our rate of
nitrogen fixation, we are in dangerous risk of causing unfavourable change.
While we may not
exactly know exactly how ecologically detrimental the crossing of these
boundaries are on a global scale, it can be argued that the destructiveness of small-scaled local and
regional ecological disasters we now observe should at least put considerable
caution in our step. Why action now and not later? The argument for that given
the "multiple-states" behaviour which ecosystems exhibit, preventive
action now will still be rather effective as compared to curative action later
which might have little effect. Better stewardship in these areas now not only
prevents us from entering that latter state but also enhances the systems
resilience (i.e. makes the hump in between higher by increasing redundancy in
the system). Rockstrom et al. argue that we do have the ability now for to
adopt this paradigm shift in our mindset and "turn crisis into
opportunity" if governments and
people come onboard. Needless to say this is a big if. And this if depends on
whether there are exist more modern, smarter and cheaper solutions of farming.
Additional References:
http://news.thomasnet.com/green_clean/2012/06/17/do-planetary-boundaries-exist-and-does-crossing-them-result-in-catastrophe/
Food Politics: What
Everyone Needs to Know. Robert Paarlberg.
2010. Oxford University Press.
Food and
Development: The political economy of hunger and the modern diet.
The political economy of agrarian change, an essay on the green revolution. Griffin. 1974. http://www.cabdirect.org/abstracts/19766710734.html;jsessionid=D7741B36A23D3E120F3DA6A010C70997
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