Forests: Adaptation and Mitigation of Climate change
Sanjay Kumar Srivastava, IFS
Conservator of Forests- Vigilance
Office of PCCF, Gandhinagar, Gujarat
Email: [email protected]
Phone: 09825553505
Title: Use more timber for climate change mitigation
Abstract:
Climate change is an accepted fact of life today. The whole world is worried and is really concerned
to find ways of its mitigation. It is a well known fact that forests are important for mitigation of
Climate change but in general forests are considered as one of the many options. The paper focuses
not only on the importance of forests as a mitigation tool but on the essentiality of the same. The
paper also focuses on the necessary adaptation in management of forests to ensure the mitigation
effect. It also focuses on certain myths and wrong polices and suggests more logical solution to the
problem. The paper tries to prove with pure and simple scientific logic that promoting use of timber
has to be central to reduce CO2 in the atmosphere and hence sustainable harvesting of forests is also
essential to control climate change.
Key words: Climate change, carbon sequestration, timber, photosynthesis, wood-substitutes
1) Introduction: Importance of forests or tree is well-known. Today even a child knows that they get
oxygen from trees. Due to sustained efforts of government and many other organizations there is
good awareness about the problem of climate change and also that the solution lies in trees or forests.
But most of the action ends up only in rallies, runs, poster competitions, essay competitions, slogan
competitions etc. They fail to realize that no amount of such actions can actually mitigate the climate
change. In addition due to the lack of understanding of few basic scientific concepts and
overzealousness to protect forests at any cost, it has also resulted in certain wrong policies like
banning of green felling and promoting wood substitutes etc. The decisions are more knee jerk and
populist than based on sound scientific logic. It can be proved easily with pure and scientific logic
that as far a carbon sequestration is concerned there is really no alternative to a tree. And that to have
the carbon sequestration effect in a sustained manner sustainable harvesting is equally essential.
Accordingly, it is not only important to recognize forests as an essential tool for mitigation of climate
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change but also to make necessary
changes
in management or in other words make certain
adaptation to actually get the mitigation effects.
2) Understanding the science behind the carbon sequestration: It is a well known fact that a plant
takes in CO2 and gives out O2 or in other words purifies the environment, but we need to understand
how after all a plant does purify the environment. And is there any way to quantify the amount of
purification done by various plants? Is every green tree doing this with same speed irrespective of its
age?
a) There is nothing magical or unknown about the process. The process which purifies the
environment is a well known process i.e. photosynthesis and there is an empirical but
unambiguous way to measure the amount of purification done by a plant. Photosynthesis is a
natural processes that uses CO2, releases O2 and produces various forms of sugar ie C6H12O6 in
the presence of sunlight. The chemical reaction is
6CO2+ 6H2O  C6H12O6 + 6O2
b) The byproduct of the photosynthesis is sugar or C6H12O6 of which most of it gets converted to
cellulose having chemical formula (C6H10O5)n or wood. The physical manifestation of the
photosynthesis is the increase in volume and weight of the plant.
c) There is a direct correlation between the amount of CO2 sequestered and O2 produced with the
amount of biomass produced. In other words if the tree is not growing in volume it is not a net
sequester any more.
d) It is possible that the rate of sequestration of CO2 may differ from plant to plant, which is also
evident from the fact that different tree/plants grow at different rates, but the sum total of the CO2
sequestered has to be proportional to the biomass produced.
e) While it may appear to be too basic or rudimentary to discuss this in a paper like this but it is fact
that even most of the educated people also feel that anything green must be converting CO2 to
O2. They do not realize that plants also consume O2 by the process of respiration and hence the
net sequestration effect of a plant must be measured by the weight gain rather than just greenery.
They fail to realize that a plant may not be net sequester (or a poor sequester) in totality especially
when the tree has crossed an age.
3) Why emphasis on trees? Now the issue comes that if photosynthesis is the key to carbon
sequestration then why emphasis only on tree as every plant undertakes photosynthesis. Here, it is
important to understand that though the primary output of the photosynthesis is carbohydrate ie
C6H12O6 it is the extent of the conversion to cellulose and the form in which it gets stored, that makes
a tree different from other plants. In case of trees the bulk of the carbohydrate produced is converted
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into cellulose (timber) which if managed properly can keep CO2 blocked for a period of 5-200 years.
In case of smaller plants it is either burnt, consumed or decomposed within a year or so releasing the
entire CO2. Hence, though even the smaller plants can also sequester CO2 but the form in which they
do, cannot store the CO2 for a period of longer than 2-5 years on average.
4) Science of tree growth: Typically there are three phases in the growth of a tree i.e. juvenile phase,
full vigour phase (maturity) and senescent phase. A typical growth curve for a tree is shown in Figure
1. The initial phase lasting for few years 1-3 years is a slow growth phase when the tree is basically
trying to establish itself. The second phase typically ranging from 4 to 80 years is full vigour phase
where the tree grows at almost same rate for the entire period. The third and final phase i.e. the
senescent phase is a phase when the growth rate slows down and virtually stops. This is slightly
different from popular perception. Normally we feel that a tree grows indefinitely but that is not true.
Figure 1: A typical growth curve for a tree in juvenile, mature and senescent phases 1
5) Current annual increment and mean annual increment: Current Annual Increment (CAI) is
increase in the total volume in a particular year. Mean Annual Increment (MAI) is the total volume
divided by the age. A typical CAI and MAI curve is shown in Fig 2.
Figure 2: A typical Current Annual Increment (CAI) versus Mean Annual Increment (MAI) curve for
a tree 1
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If we look at the above curve carefully it can be inferred that the growth is not always at its optimum.
In the initial phase it is slow, then it peaks and then it drops down and virtually stops. It can be shown
that if the volume alone is the desired output then the tree should be harvested at the age when CAI
equals MAI. If rotation is maintained at the age where CAI equals MAI then the output of timber is
maximized from an area. And in fact this has been the basis of the traditional forestry when forests
were managed mainly for timber.
6) Difference between a green and growing tree: Normally it is assumed that a tree if green must be
sequestering CO2 but that may not be the case. There is a difference between a green tree and
growing tree. While all growing trees will be green but all green trees may not be growing. Being a
biological species a tree does not grow indefinitely. As mentioned above after some time the rate of
growth slows and ultimately virtually stops. It may remain green and alive but its growth will
virtually stop after a time. Logically if a tree is sequestering CO2 it would show as an increase in the
volume of the tree and vice-versa. So, a fully grown tree which is not growing in volume may remain
green and may be good for wild life but is doing no good to the environment as the sum total of CO2
taken in and given out (in the process of respiration) almost balances each other. That is the time it
should rather be removed and used as timber and make way for new plantations. This has been the
basis of traditional forestry but unfortunately because of half understood concepts few people
advocate total ban on green felling without understanding that it is ultimately doing more harm than
good.
7) Can there be any artificial method carrying out the reaction of photosynthesis? Theoretically it
may be possible to carry out the photosynthesis process artificially but the fact remains that it will
ultimately produce more CO2 then it will sequester. This is because photosynthesis is an endothermic
process. It needs 686 kcal per mole of glucose. No matter what process we adopt we will need that
much of energy to carry out the reaction. In nature the process gets energy from sunlight but for
artificial reaction we need to produce that much of energy in some way. If we leave the electrical
energy produced by non-fossil sources there is no way to produce equivalent energy without
producing equal amount of CO2 at the least. And if we use non-fossil energy then we should better
use that energy to replace energy being produced by fossil fuels rather than using it for something that
nature is anyway doing in abundance. So the idea of carrying out the process of photosynthesis
artificially is of no use to fight climate change.
8) Various methods of carbon sequestration under discussion: There are few other carbon
sequestration methods proposed or discussed at times but all have their limitations as explained
below:
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a) Sea: Sea itself keeps a lot of CO2 dissolved. The two main sources are respiration by aquatic
animals and absorption from atmosphere. But logically the amount that can be dissolved will
saturate at some point. This saturation amount will be a function of temperature. The moment
temperature increases beyond a point all the CO2 will come out. It is also not possible to control
the temperature of sea hence it is not possible to use sea as a carbon sink. In other words it is a
process beyond the control of human being hence cannot be part of mitigation efforts.
b) Phytoplankton: Phytoplanktons are photosynthesizing microscopic organisms that inhabit the
upper sunlit layer of almost all oceans and bodies of fresh water. They take in CO2 and produce
O2 as the part of the process of photosynthesis. They are the basic energy source of the entire
aquatic life. But since they do not convert the sugar to cellulose, their shelf life is very less and is
invariably consumed by some aquatic animal or other in no time and enters into the food web of
aquatic life and hence the captured CO2 is released by way of respiration. Though it is possible to
promote the growth of phytoplankton but it is not possible to restrict its consumption meaning
there by beyond a point CO2 cannot be stored by this method. Theoretically it is possible to
create bio-fuel by farming phytoplankton but so far it has proved to be unviable. In 2013, Exxon
Mobil Chairman and CEO Rex Tillerson said that after already spending $600 million on
development in a joint venture with J. Craig Venter’s Synthetic Genomics since 2009, algae is
“probably further” than 25 years away from commercial viability 2. Hence this cannot be taken as
a possible solution.
c) Coral Reefs: Coral reefs are also considered as a good carbon sink. But this is also not a possible
solution to sequester carbon. The CaCO3 being formed the coral reefs apparently fixes the CO2
molecule. But the Ca++ ion which is used is itself released from some CaCO3 molecule after
releasing a CO2 molecule. The reason is that calcium being a very reactive element cannot be
found in native form in natural conditions but only in some compound form. On the earth crust
most of the calcium is found in form of CaCO3. And the Ca++ is released only when CaCO3 gets
dissolved in water. So every CO2 thus fixed will produce one CO2 molecule somewhere else.
Hence by this method also there is no net carbon sink effect.
d) Sequestration of carbon in geological formations: There are certain suggestions that we can
capture CO2 and push it inside some geological formation and store it there for eternity. This idea
has also some basic flaws. Obviously this method can be applicable only when we are near to the
CO2 producing spot else we will have to spend enormous amount of energy in just separating
CO2 from air. There have been some attempts to do so and in fact the method is actually being
used in increasing oil production by oil producing companies. But since it is practically not
possible to tap each and every source of CO2 the amount that can be blocked this way will not be
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even tip of iceberg. Further since even in the best of case CO2 is stored in gaseous state it has
every chance of coming out from some other outlet. In addition since we have to push the air
inside and also ensure that it does not come out or in other words we have to keep the CO2 in
pressurized condition we will have to spend lot of energy just to store it and eventually give out
more CO2 than possibly we can store this way. In a nutshell though it might be possible to pump
CO2 directly in the geological formations but looking at the magnanimity of the problem this
does not offer any real solution.
9) Essentiality of Carbon sequestration: There are few scientists who doubt the theory of Climate
change and hence there could be some difference of opinion on the possibility of climate change but
one thing where there is no ambiguity or difference of opinion is that there has been steady increase
in CO2 level in last few decades. And by any stretch of imagination this cannot be sustainable and at
some point of time it will show some adverse impact on the climate. Manner and extent of effect
could be a matter of debate but essentiality of some adverse impact cannot be doubted. So obviously
it is very much essential to keep the CO2 level under control. Now one obvious method is to reduce
the emission for which lot of international efforts is going on in terms of CDM and REDD+ but still
fact remains that reduction in emission alone cannot keep the CO2 level under control. It can at the
best slow down the process but can never reduce the CO2 level. For reducing emissions, sequestration
is essential. So basically we have a situation where sequestration is essential but there is no other
method apart from a growing tree to do so and hence forest automatically becomes essential when we
talk about mitigation of the climate change.
10) Even if we assume an overgrown tree is no more sequestering CO2 then also why not just leave
it standing? What additional benefit is there in harvesting it? : As explained above once a tree
attains maturity it does not grow and hence does not sequester CO2 any more, but leaving it as it is
will take away the potential of that particular land to host more trees which would have sequestered
more CO2. Cutting a tree per se does not emit any CO2. Using a cut tree for making durable wood
products does not emit CO2. It is emitted only when it is burnt. Further if we do not cut the mature
trees then we will be forced to use the wood substitutes i.e. steel, aluminum, plastic and concrete.
These substitutes will invariably produce more CO2. Now since the human requirement of some
material to make furniture, houses etc cannot be reduced beyond a level it is better to use wood rather
than its substitutes. So logically we need to start substituting steel, aluminum, plastic and concrete
with wood as much as possible. The only care that need to be taken that the wood product needs to be
properly seasoned and protected for longevity.
11) Soil Carbon: Empirically it is accepted that on an average 20% to 50 % of the biomass is under the
soil in typical conditions. But just by cutting the tree it does not come out. If there is no increase in
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the biomass above ground then there is also no increase in biomass underground also. The above
surface litter has very short life and does not add much to soil carbon. Soil carbon is depleted mainly
by the land tilling practices. Just by felling a tree and planting a new one is not going to have any
adverse impact on the subsoil carbon. Studies in boreal forests have demonstrated that tree harvesting
generally has little long-term effect on stabile soil carbon stocks3 (Martin et al., 2005). There have
been many similar studies which have shown clearly that there is no conclusive proof that harvesting
leads to soil carbon depletion4 (Johnson et al., 2002).
12) Heat stored in plants: Not so evident but another important contribution of a growing tree is that
apart from conversion of CO2 to O2 a growing plant also absorbs heat. This is nothing but the
sunlight that would have otherwise converted into heat had it not been used for photosynthesis. This
is also why we feel cooler under a tree. So a tree also helps the climate change by storing heat which
otherwise would have added to global temperature. Above stated facts can be understood logically as
follows. Suppose we cut a tree and burn it. We get mainly two things: CO2 and heat. By simple logic
of conservation of energy and chemical constituents it can be concluded that the amount of heat
emitted and the amount of CO2 emitted is the amount of heat and CO2 respectively absorbed by the
plant while growing. So a growing tree not only sequesters CO2 but also absorbs heat which
otherwise would have added to the heat in the atmosphere.
13) Adaptation in management of forest: Presently the forest management is overtly conversationalist.
For one reason or another and more so because of environmental lobbies in general there is strong
opinion against any kind of felling of trees. There is a strong case to have a relook at this approach
and take a more pragmatic and scientifically sound approach. So far whenever one talks about
adaptation of forest with reference to climate changes then we talk about change in practices so as to
cope up with the situation. But the biggest change or adaptation that is needed is the way we manage
forest. As explained above, growing forest (coupled with sustainable harvest practices) is the only
meaningful way to sequester CO2 hence they are essential for meaningful mitigation of climate
change. But mere realization is not sufficient. We also need to adapt the management and change
over to judicious production oriented forestry from overtly conservation oriented forestry to actually
derive the mitigation effect of the forest.
14) Conclusion: Following changes or adaptation in the management of forests are suggested:
a) It needs to be accepted as a policy that growing trees is not just one of the many methods of
carbon sequestration but that it is the only meaningful method of carbon sequestration. Since
there is nothing on the planet other than a growing tree that can reduce CO2 so tree planting has to
central to be any program of combating climate change.
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b) Where ever possible we should use timber rather than its substitutes. Any substitute of timber is
going to produce more CO2 in most of the cases. Government and big organizations should
aggressively promote the use of durable wood products. For long term it is much more beneficial
to promote use of timer use rather than its substitutes as it is the only meaningful way to store
CO2. By promoting timber use we will block more CO2 than otherwise.
c) Further increased market for timber would allure people to produce more timber. Rather to make
it a viable economic activity without any risk government should specify some Minimum Support
Price for selected timber species.
d) Fuel-wood use should be discouraged as there are efficient ways of cooking food. The non use of
fuel wood would lead to more decomposition of wood thereby increasing the humus content in
the soil and thereby increasing productivity of soil.
e) Plywood and particle board industry needs to be promoted in a big way as it helps in using even
the inferior quality of wood to be used as timber which otherwise would have been used as fuelwood there by blocking more CO2. Similarly seasoning and treating wood should also be
promoted as it increases the life of timber.
f) There is a general perception that using wood is not good for environment. There is need to
educate public about the benefits of using more timber. Slogans like “Wood is good” should be
aggressively promoted.
g) Governments should relook at the forest management policy which is overtly conversationalist
and switch over to scientifically correct policy of sustainable management.
h) Such a strategy is not being suggested for existing forest area under protected area network as
such as even standing tree keeps the CO2 blocked. In addition they support the invaluable flora
and fauna and have other beneficial effects on environment like increasing precipitation,
decreasing soil run off etc. So for forest area such a strategy should be taken with modifications
on a case to case basis.
i)
This strategy can be definitely taken for promoting social forestry outside forest area in a big
way. In fact more than 76% of the land area is outside forest and most of it is much more
productive than any forest area. By promoting use of timber and assuring market by minimum
support price government can promote raising of timber trees and optimally utilize these areas to
fight climate change. The success of agro-forestry models in Punjab, Haryana and Andhra
Pradesh has proved that given the right conditions farmers embrace such models in a big way 5.
Such an approach will also make India self sufficient in timber wood and will save huge amount
of foreign exchange being spent on importing timber.
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j)
In a nutshell it must be realized that though forests are essential to support biodiversity but at the
same time their sustainable harvesting is equally essential to sequester carbon and thereby helping
to mitigate climate change. So a balanced view is needed in management of forests rather than
being overtly conversationalist.
References
1.
Cristopher L. Brack and Geoffrey B. Wood Tree growth and increment, 1996. URL:
http://fennerschool-associated.anu.edu.au/mensuration/BrackandWood1998/T_GROWTH.HTM
2.
Web: http://en.openei.org/wiki/Definition:Algae_fuel
3. Johnson, D.W., Knoepp, J.D., Swank, W.T., Shan, J., Morris, L.A., Van Lear, D.H.,
Kapeluck, P.R., 2002. Effects of forest management on soil carbon: Results of some longterm re-sampling studies. Environmental Pollution 116, S201-S208.
4. Martin, J.L., Gower, S.T., Plaut, J., Holmes, B., 2005. Carbon pools in a boreal mixed-wood
logging chrono sequence. Global Change Biology 11, 1883-1894.
5. P Lal, Role of Private Sector in Agro-forestry and Supply of High Quality Planting Stock,
Indian Forester, Volume 134, Issue 5, May 2008.
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