Science Society Sustainability
http://www.i-sis.org.uk
ISIS Press Release 03/03/05
Multiple Uses of Forests
A global trend away from monoculture tree plantations towards
multiple uses of native forests is good for conserving forest
ecosystems, but progress is hampered by a dominant paradigm that
treats forests like cornfields. <mailto:[EMAIL PROTECTED]>Dr.
Mae-Wan Ho
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All commercial forests should be managed for multiple-use
Dr. Erkki LŠhde, Finland's foremost forestry scientist, is convinced
that forests can no longer be divided into those focussing on timber
production and others with multiple uses. Instead, all commercial
forests, in Finland and elsewhere on our planet, should be treated
with their multiple uses in mind, in order to sustain their ecology
and biodiversity in a 'close-to-nature' state. Merely safeguarding
the productivity of timber and pulp - in monoculture plantations -
while preserving 'key biotopes' in their natural state is no longer
considered sufficient for species conservation.
I met Dr. Erkki LŠhde very briefly while on a hectic lecture tour in
Finland in November-December 2004 as guest of Finland's People's
Biosafety Association, and immediately recognized the profound
significance of his work.
The emphasis on multiple uses of commercial forests is particularly
important for many indigenous peoples who have been an integral part
of forest ecosystems for millennium; whose livelihoods are being
threatened by deforestation, which includes replacing native forests
with monoculture tree plantations.
Monoculture tree plantations are anathema to the biodiverse native
forest ecosystems of the world. The United Nations Environment
Programme (UNEP) estimated that about 60 percent, and possibly closer
to 90 percent of all living species are found in tropical forests.
Thus, adopting multiple uses of forests that can sustain their
biodiversity is extremely significant for conserving the earth's
species; and there has been a growing trend towards doing just that,
though not quite fast enough.
Recent research in Mexico also shows that cacao and coffee-based
agroforestry systems managed with low inputs by small holders harbour
significant biodiversity compared to the monoculture plantations (see
"Agroecology versus ecoagriculture", <http://www.i-
sis.org.uk/isisnews/sis25.php>SiS 25).
A major obstacle is the prevailing paradigm that treats natural
forests like cornfields
One major obstacle to adopting multiple uses of forests is the lack
of a good model of the natural forest ecosystem. "The prevailing
paradigm still treats natural forests as if they are cornfields,"
says LŠhde, "The entire stand is supposed to be destroyed at certain
intervals by natural disturbances such as forest fires or storms.
After that a new forest would grow from the saplings."
Based on that model, thinning and clear-cutting forests are routinely
carried out to this day. The smallest and youngest trees and the
under storey are cleared away, leaving uniform trees standing like
"rows of carrots"; and when the trees are ready for harvesting, they
are clear-cut, and the stock replaced. This is said to 'mimic'
nature. More accurately, it is supposed that natural forests imitate
their cultivated counterparts, producing stands of trees that are
uniform in size or age.
However, when real forests are examined, they tell a very different
tale; there are no uniform or even stands of trees. Instead, native
forests - especially mature and long established forests - tend to
have diverse, uneven-sized mixed stands.
Forest trees come in all sizes
Finland was the first country in the world to carry out a national
forest inventory as early as the beginning of the 1920s. The
inventories have since been repeated once every decade. Measuring
tree diameter at breast height has been one of the ways to
investigate forest stand structure. It fell to the lot of LŠhde and
his research team to carry out the ninth inventory in the early
1990s; and for the first time since inventory began in Finland, the
distribution of stem diameters of the trees was published.
LŠhde went through the old inventory data for advanced and mature
forests in Southern Finland for 1920s, 1950s and 1985. He found four
possible distributions in the data: even or uniform sized,
two-storeyed, "moundy uneven-sized" (normal distribution), and
"regularly all-sized" (see Fig. 1). The vast majority of advanced and
mature forests had the "regularly all-sized" distribution. This was
also true of data from the Swedish National Forest Inventory.
Fig 1. Different distributions of tree sizes and their percentage
occurrence in natural or mature forests in three surveys carried out
in 1921, 1951 and 1985.
Biological significance of the "all size" distribution
The "regularly all-sized" distribution discovered by LŠhde and
colleagues for the stem diameter of forest trees is commonly referred
to as the 1/f distribution, where f is the frequency of the size
class. It says that the frequency of the size class varies inversely
as the diameter: the bigger the trees, the less frequently they
occur. The 1/f distribution is possibly the most significant 'law'
discovered within the past 15 years for natural processes ranging
from earthquakes and avalanches to the branching of trees; and is
especially relevant for biology (see "Living energies" series,
<http://www.i-sis.org.uk/isisnews/sis21.php>SiS 21). This
distribution is characteristic of fractals - such as coastlines and
trees - which have fractional dimensions between the usual 1, 2 or 3;
as well as the same or similar structure over many scales.
I have suggested that the "regular all size" or fractal distribution
applies to the totality of species in an ecosystem, which enables the
ecosystem to maximize energy capture and storage and minimize
dissipation. Translated into biological terms, it would predict an
increase in biodiversity and productivity (see "Energy, productivity
& biodiversity" and "Why are organisms so complex? A lesson in
sustainability", <http://www.i- sis.org.uk/isisnews/sis21.php>SiS 21).
Sure enough, there is evidence for that in forest ecosystems. The
"regular all size" distribution supports more biodiversity of trees
and higher productivity, and any measure that destroys that fractal
structure diminishes both.
LŠhde and his colleagues calculated the diversity index of trees in
forests with the four different distributions: the even sized stands
scored 7, the two- storeyed stands scored 15, the "moundy", 21.5, and
"regular all-sized", a clear winner at 39.5.
Researchers in the Canadian Forest Service in the forests of North
Central British Columbia had previously shown that the impact on
biodiversity was dependent on the method of harvesting, with
single-tree selection and group selection causing the minimum damage
(see Table 1).
Table 1. Harvesting method and diversity Treatment Diversity (%)
Untreated 100 Single-tree selection 90 Group selection 80 Shelterwood
cutting 55 Remodelled clear- cutting 24 Seedtree cutting 20 Clear
cutting 5
LŠhde and colleagues compared the productivity of even-sized stands
with uneven- sized stands in experimental plots in southern Finland.
The results (Table 2) showed that clear cutting leads to unstable
wood production. During regeneration and sapling stages, growth
remains low, reaching its peak only when maturing. At maximum, it is
still lower than the average production of regularly all-sized
stands. Thus, the latter are more productive and more profitable on
average than even-sized stands. The quality of the wood produced is
better and it is able to sustain multiple uses on account of its
higher diversity.
Table 2. Productivity of even-sized and uneven- sized stands
Stand/developmental stage Volume m3 CAI* m3 Clear cut area 0 0.0
Regeneration area with seed trees 28 0.8 Regeneration area with
sapling stand 26 2.7 Young thinning stand 140 5.1 Advanced thinning
stand 178 5.1 Mature stand 180 4.4 Regularly all sized stand 194 5.9
*Current Annual Increase
In the short- term, clearcutting is a cheap and technically easy
option, and hence "an obvious favourite of the forest industry" which
enjoys the full benefits while leaving forest owners to bear the
costs of long and often expensive process of regeneration. "Then, not
only the timber production is at its minimum but the multiple use and
sales values of the forest are also at the lowest." Furthermore, the
risk of failure remains high throughout the regeneration process.
Somewhat surprisingly, low thinning of small trees - a common
practice in forestry carried out in the belief that it favours the
growth of large trees by removing "competition" - also reduces wood
productivity (see Table 2). And this was confirmed in another set of
experiments involving 23 Norway spruce-dominated experimental stands
extending from southern to northern Finland, where LŠhde and
coworkers found that CAI averaged 5.4 m3ha-1 in single-tree selection
plots compared with 4.6 m3ha-1 in low thinning plots.
The reason why single-tree selection favours wood growth, they
suggest, may be because removing slow-growing dominant trees releases
space and nutrients to enable small trees to grow more rapidly; while
removing small trees in low thinning results in little or no benefit
for the remaining dominants.
Tree plantations do not make economic sense
In order to counter the market-driven economic arguments all too
often used to justify the destruction of our natural resources, there
have been valiant attempts to estimate the value of 'ecosystem goods
and services' in monetary terms.
An international team of conservationists led by Andrew Balmford in
Cambridge University, UK, estimated the monetary value of benefits
from relatively intact biomes compared with those converted to
intensive human use. These include the tropical forest in Malaysia
under reduced impact logging as opposed to conventional logging, and
the tropical forest in Cameroon under reduced-impact logging or
small- scale farming as opposed to conversion into oil-palm and
rubber plantations.
In the case of Malaysia, the high-intensity, unsustainable logging
was associated with greater private benefits through timber
harvesting, but reduced social and global benefits through loss of
non- timber forest products, flood protection, carbon stocks and
endangered species. Summed together, the total economy value of the
forest was some 14% greater when placed under more sustainable
management.
In the case of Cameroon, conversion to oil palm and rubber
plantations yielded negative private benefits, while social benefits
from non-timber forest products, sedimentation control, and flood
prevention were highest under sustainable forestry, as were global
benefits from carbon storage and other values. Overall, the total
economic value of sustainable forestry was 18% greater than that of
small-scale farming, whereas it was negative for plantations.
The total economic value of sustainable uses of the forests were
underestimated in that report, as only a handful of well-established
ecosystem services were considered, while some particularly valuable
services, such as nutrient cycling, waste treatment and the provision
of cultural values were not examined.
It would appear that forestry is in for a complete shake- up, if we
are to make the best use of a resource that's essential to the
survival of our planet and its teeming biodiversity.
This article can be found on the I-SIS website at
http://www.i-sis.org.uk/MUOF.php
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