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1
World Forests
A bout 30 percent of the world's ice-free land surface is occupied
by forests and woodlands. Permanent pastures for livestock (24
percent) and arable lands under crop production (11 percent)
also contain significant numbers of trees and woody shrubs that provide
a variety of services and products for humans (Food and Agriculture
Organization, 1988~. The decline and loss of the forested portion of the
globe have been vast and have caused grave concern among scientists
and policymakers worldwide.
The forested areas of the world now comprise between 3.8 billion ha
(Council on Environmental Quality and U.S. Department of State, 1980)
and 4.5 billion ha (Table 1-1~. The coniferous forests of North America
and Eurasia cover an estimated 1.3 billion ha, other temperate forests
about 1.1 billion ha, and tropical forests about 1.7 billion ha.
LOSSES IN FORESTS
Although major losses have also occurred in temperate forests, the
greater concern is about losses in the moist tropical forests, which
comprise the most complex, species-rich ecosystems in the world (Office
of Technology Assessment, 1984~. These forests are being destroyed at
Tree species discussed in this report are identified by their scientific names. The use of
common names is complicated because many may exist for a single species, they may
refer to only a portion of that species, or none may exist for some species. Where clarity
could be improved, common names supplement the scientific names.
21
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World Forests / 23
an unprecedented rate. The commonly accepted estimate (Lanly, 1982)
is that the net annual loss amounts to 11 million ha, an area the size of
Guatemala. Closed forests in the moist tropics, those that have a mostly
continuous canopy that collects a high degree of sunlight, are being lost
at an annual rate of 7.5 million ha. Open formations in drier areas are
declining by 3.8 million ha annually (Grainger, 1987; Wood et al., 1982~.
In the dry tropics, semiarid vegetation types and Savannah woodlands
are being turned into wasteland at a rate of about 2 million ha annually.
About 36 percent of the tropical forests that have been degraded by
removal of natural vegetation and overcropping could still be rehabili-
tated with the introduction of tree species. This includes 418 million ha
in dry or montane areas in need of reforestation, 137 million ha of
tropical rain forest in need of protected regeneration, and 203 million
ha of forest fallows in the humid tropics in need of reforestation (Wood
et al., 1982~. In India alone, there are over 100 million ha of wastelands,
an area the size of Egypt, and vigorous attempts are now being made
to revegetate those lands with tree species to restore them to productive
use (Hegde and Abhyankar, 1986~.
If the deforestation rates in the Caribbean and in Central and South
America remain constant, the reduction in forest area by the end of the
twentieth century will result in the loss of an estimated 15 percent of
all currently identified plant species and 2 percent of all of tropical
America's plant families (Simberloff, 1986~. If the rate remains steady,
it is also predicted that 66 percent of the plant species and 14 percent
of the plant families may disappear by the end of the twenty-first
century (Simberloff, 1986~. These estimates are based on the number of
species that are known to science at this time. Research and exploration
activities may discover many new plant species, which in turn may
increase estimates of the number threatened. Even at the current rate
of destruction, catastrophic losses in plant biodiversity are likely and
the loss of genetic resources could be substantial.
The loss of forest genetic resources is not confined to the tropics.
Especially in Europe and North America, atmospheric pollution and
wildfires have threatened forests and the genetic resources of a range
of species (Scholz et al., 1989~. Degraded forestlands and watersheds
may be rehabilitated, and denuded hillsides afforested, but when a
species becomes extinct, or genetic variation is reduced, the loss is
permanent. Even if forests are regenerated by natural or artificial means,
they may become less capable of genetically adapting to environmental
challenges and to future large-scale stresses.
The loss of valuable plant genetic material could be even more
significant in little known species that may have small distributions but
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Representative terms from entire chapter:
world forests
~ /: ~!
12
.., .
12
S
11
These h~o~sate!l~)tei~
a: ~ ~ ~ ~ ~
^~ ,~ / ~
a:
s
~ ~ :~
w51 ~
~ if:=
!
O
a:
at the end of the Bag is cloud Over. Me image on We fight shams the same a~a
on June 1S, 19~, Ails the add~i~Son of Ceder roads add geared land. Credit:
l~nstituto de Penguins Es~#is (INPE), ~o Josh Dos ~Campos, Brazil.
ist~h~eirabili~to spend fume en~v~iron~men.~istesses~Yanaseme~nt
inte~~n-tionsint~h~e ~:mainin~ ~res~t~s,event~h.ose~naturallyrep~roduced,
illbeaf~ctedbvand ~111 further affect the strung of ~enedc variation
of any future ~rests.
B^S1C I~O~
. . ~
(~neofthe mostbasirp~ble~s~fadngconserati~onand management
egos for Wrest spades is inad~ua~ and uneven inventor dog on
the distribution and abundant of trees. Kiln great Britain, far example,
^ ~ ~ ~ ~
egg peg so Is mapped on a computed 1~2 Id
system' hat topical areas have net been Piped Span less detailed, 210>
km adds (Prince, 19~). gang forest Me spews Specially in the
humid ~pics<~ma~ ~undesc~d as a res~l~t; there is ho ample
11 Tent of genetic Souses, evens at the species level
He cu~be~ome and elusive cactus Of a complete #rest inventor
{Dora) on be Placated ~ go ells died sites. Baeo ~Cplo~do Island
(Big) ~ gag (lope ha) and ~ ~Selva~ ~oIo~c~I~ fueled On of the
9a id! Tryp~al~S~tud~i~ ~ cods ~ca~{l:.~O bay Ears atonal
. .
~ ~ ~ ~ ~ ~ , ~ ~ ~
tale Sloppy ~st~no~n tropical rain ~~s<~. Me ~ of BC1 took
almost lo Beers to tom)Je~te (Cat, 19~)~. ~Tbe ~ork~t-~a~ a ~scb~pIe~
~ .. · · . ..
nora of ~ Sedan ~as~initiated~ in the em ions, and flit is Cited
to be the Beady Laps ~ Bog is p~lis~d.- Spite gut that
the spews in Tab loaf the areas have ~ep!~th#roig$\ recollected over
the past ~Z3 years' sneak Eden are con~dn~ua~y~Bei~g Id. For
example/ 15 anew species =~e been found at BC1 since we ~p~lcatlon
of Crates frog (Gen<, 1~:
ad- ~~~ :~ dog
The Eigh!#en:th ~ filed C~op~gress~(i#~1~984)ofth~ln~ternitio~al Anion
ofForestryResearch~Org~rlzations(l~ RO)~re~pjp~eS halo m~j~orio~est~
re~latedth ~ tsar ~ os~hetit F~ollotion!~/d~d6(ores3bo!n.
~ third direat~1s~th~e as ing of the frenetic base A~ a result of
com~me~dalforestry operations
Pa ~ ~ ~
lathe temporal regions' Dilution roam industrial and transportation
ac~vibes,combi~ned ~ithothe~rstresses,iscausing~seve~redeclinein
~restviSor(~Scholzetal.,lSS9~.Them~ostsevereef~ctsappea~rto ~
occ~rdnginCe~na~n~yandCzechoslovaUa,buttreesaredvinSprema-
t~re~lvi~n~mostind~st~al~edcounthe~san~dinsomedev~el~ori(~co~u~nides.
.^ ~ ~ , ~ , ~ , , . .., .. . ~ ..
~e~4
~ ~ /27
La~e~scale clowns of ~1~1 clan ~rest IBM fine Amazon Plasm, Colas, cam,
never Me Rio T~n~tins, yes photdg~phed in 1~. Clad ec~ngles 3~
plant ions whew natu^1 woodland fleas ~pid~lv being convert to pastureland
far Male Branching and a~^l~t~1 land far Swoops, such as maize and bung
calve. Smoke dsi~ns Cam a O~ burning amp residue or brush uppers in the
cater of the phos~~ph. Credit: NaEtiona1 Ae~~nau~cs and Space A~dmi~nist~-
tion.
Dee
Although evidence exists of the effects of pollution on both temperate
and tropical Breasts, de~re~sta~on is ~co~gnized as the Valor threat in
the tropics festoon is associated With the following activities
(Evans, 1982):
~~} ~1
producing firewood and charcoal,
spend ~o~nz) cul~va~on,
~ ~ a....
. .
Momma
,. , .
en upon am ~ .u~ ~'
/ ~i ~
~ over zing and fiddler doIle~io!n,
-aim ~bE#~z (accident fir d~l~ra~, and
:~:
Tat first Our activities age the mast si~niica~pt -~ a {o~}.~p~rs~pe~bv~
~~d her. P~~ AL #~ p~d^~s/~s~s
as Judd ~ anus and ~1 pave also head significant em Joan The
degree -~hi~ch~nds agree detested
plead Air s~'tio~nary attune figs ^curdn) in all Most types; but
iota is most ex~ns~e in moist tropism beasts. ~o~pici1 Restore ~<
. .. .
<#aide ~ planting in~dustria~1 pe~e~hn~ial Ups, subbed Soil ~ paid
Or trees. and Air cattle I in Soutb gamete lands the Ode
~ ~ ~ ~ _ ~ ~ ~ ~ ~ _ ~ ~ ~ _ _ ~ ~ ~ ~ ~ . ~ * ~
islands. Aft Savannah Hand is allow aging cleared to create small.
miked!-use Beans 1n!te~sive fling ~ g is~o^~rr~ni throughout maw
counties ind'~pitb~e value offend hi~rd~ood~timbe~ incre~se~s/~ore
^~mdie~restsarebeco~ingecono2~ilW~a~tt~c~ve ~rl~.T~inin~
tees am i~s~.:fE
An oak Savannah ~ Si~Eru~\, Turkey, ash -q p~rtia~}v~ha~eted tar fuel
prods. Me flogs in the ~g~u(~ ~11 ~ matte gins >>a~1 and sold in
u~/ba~na~reas.Cred-~t:C~lvin~R.Sp~Jing
mop plaints from the use dt~
advised ~pu~bo~ ~ ads ~~ guess have Nan Ed to
meet specific ~q~u~-ments and in Which genetic viriati-o~n may be
drolly added As with agdc~J~1 crops, breeders land to maxi~-
m~e the Capon. of these new populations to large~scale plantation
conditions be intensive selechosn Air certain traits, own at the expense
of ~neLc O6~bUi~ and the Hanoi far Stun pda~ve Amp. It
Possible to provide genetic Oex~ibi~li.ty by breeding dif~rentJ~Y enh.a~n~d
populations for alternative ~t~ users and to maintain v\~li~ i.n
assorted types of Me popu~lad~ns, but very ~ three brewing purges
are designed to ago so. (~e the multi~ple-populatio~n breeding stately
described by {mkoon~ et al.' 1980. ~ Cn.fo~rt~.~nate~ly, sow ~eneLc looses
cannot be~reco~u~ped because current prod~ctio~nis often not backed up
by the holding cf ex~nst/e oft coercions of esed ages or by enamor
ewes to conga va^bon ~ name sandy
~ spades or a population sample of a Or pan of in genetic
Godson An ~ consumed though in ~ or ax ~# consent. In
If EMS
sin ~ cpnse~a~jon Sees both
pompon and Me evolutional
pr~es~s~S1nat enable tne po!pula~lon ~ ~gap:. hex sip ~nse~ation
Apses the je~ne~c diversity extinct in the po~p~la~ti~o~
tba~t~s~makes Spews off the preserved ~teda~1 ruddily ~
World Forests 131
is also conservation in situ. Unlike the use of this term for agricultural
crops, maintaining planted tree stands in a region where the species
occur naturally is also considered in situ conservation. Thus, protection
of artificial regeneration that results from sowing of seeds or planting,
provided the materials are collected from the same areas where the
planting takes place, is also included under in situ conservation.
Ex situ conservation, in contrast, implies that material is protected at
a place outside the distribution of the parent population. It may be
applied to reproductive material, such as seeds preserved in a seed
bank, or to trees planted in arboreta, botanical gardens, or test or
conservation stands away from the site of the parent population. Ex
situ and in situ conservation are complementary strategies. Ex situ
conservation is used where in situ conservation, for various reasons, is
impractical or too expensive to maintain. This is the case, for example,
when tree populations are under strong demographic or other pressure
and their long-term conservation in situ is thereby impossible to secure,
or when the germplasm is used in places that are remote from their
original locations. (The circumstances for employing both of these
conservation approaches are examined in Chapter 4.)
Conservation and use of tree germplasm face technical impediments
that must be solved. Trees are long-lived organisms that require large
spaces for survival to maturity and for maximum productivity. Tech-
niques for use and conservation, such as establishing biosphere reserves,
are known in principle, but little attention has been paid to the genetic
management of reserves in which species must be conserved in situ
(Palmberg and Esquinas-Alcazar, 1990~.
The reproductive biology and genetic structure of tree species do not
conform to any single paradigm. Breeding systems vary among species,
and many species exhibit mixed mating strategies. Some species flower
and set fruit in irregular patterns, which makes their outcrossing
(interbreeding) rates unpredictable. The resulting diversity of genetic
structure in a population means that different sampling patterns must
be used to ensure conservation.
The breeding cycle for trees is currently an order of magnitude longer
than that for most agricultural crops and must be accommodated in
effective conservation programs. Research is needed to develop tools
for rapid or early reproduction of trees. Because forestry must also deal
with species of little current commercial importance, methods other
than those for managing trees of the same age (even-age plantation
management) will have to be considered. These may include partial
replacement with younger trees, direct seeding into conservation stands,
and control of the size and location of areas to be harvested in the
Of ~
sta~nds.~YVh~il~e the methods ~rconsbrving ages can d. on Botany of
the tedEniques developed R~ agdcu~uralcrops,tbey may need to be
#~ ~ ~ ~ ~^ ~ , +
peculiar to nnost tree spades.
lt~i.s clear that to maximize the future global utility of finest gee
resources, ~ great deal o~fbas~ic ~d~enti~cin~r~aJon and~esea~rc~h
ur~entlv~needed.
~,
CO~PARlNC lRE~E~S~ blT8~A~Rl^L~^L CROPS
. .. t .
e
OCR for page 33
World Forests / 33
More comprehensive study should be made of the effects of global climatic
change and pollution on forest tree species.
Much attention has been focused on the potential consequences of
global climate changes brought about by increased concentrations of
heat-absorbing greenhouse gases, such as carbon dioxide, methane,
nitrous oxide, and chlorofluorocarbons. Some experts suggest that the
greatest effects of increases in atmospheric carbon dioxide, mostly
resulting from the burning of fossil fuels over the past 100 years, will
occur at higher elevations and more northern latitudes. These specu-
lations, however, remain to be substantiated by scientific study (Silver,
of programs for a few woody species (e.g., willows, eucalypts, pines, and
poplars), few tree breeding programs have progressed beyond the second
or third selective cycle.
Socioeconomic Status
The fact that forests evolve and that regeneration is susceptible to
positive and negative human influence is often not understood. (It is only
when forest products are in short supply or lacking that people realize
the need for them.) Conversely, it has been recognized for 10,000 years
that food requirements can be produced or enhanced by the deliberate
creation and management of resources. Wood itself is a low-value and
high-volume product, and food will always have survival priority over
wood products or other forest benefits.
Quantifying the value of benefits derived from trees is difficult, for
several reasons. First, many forests used today originated naturally, so
no costs of establishment or stumpage (market) values have been applied
in economic analyses. Second, some benefits, such as soil holding or
improvement, or water flow moderation, have importance to society that
is beyond their obvious environmental advantages. It is, however, difficult
to determine such social values. Third, rotations of planted tree crops
normally extend over many years, which creates difficulties in assigning
variable discount and inflation rates. Given high-establishment costs in
the early years and low-product values in later years, forestry projects
always appear poor investments unless their socia! benefits are taken into
account. The same principle applies to the allocation of funds for conser-
vation of genetic resources.
Multiplicity of Uses
There is great international interest in so-called multipurpose trees
(Burley and van Carlowitz, 1984), but in practice virtually all tree species
can be used for more than one purpose. In this respect, they differ from
many major agricultural species, which are generally grown for single
products and often for specialized uses
~ / Deaf ~
Land in Lathe Edmund (as hat ~ flu up ~ the ~up<~ of ~tbe Oxford
Pinthot~1 Few add repented With younger am. Clearest Test in
We natal Crest am vale. ln Wash~gt~ Saw, pa enthuses am
equaled to Plant load areas Within 3 veals Edit: James P. 51^ ~1
Imps an.
,
1~. Folksy tbemsel~s am ~ souses and consumes of s~s~pbe~
canon decade. TO extent to Shah existed or newly planted Masts
could Duct ~tbe a~o~hedc wonton of this As mains a super
Sac at I and degas
cadre general abetment exists about tbe ^k Preen Crest decay
and ~ll~ud~. H~ it i~ dolt to a~ ~elv He en~ron
menial and physic pathways that are acted ~ Militants.
Poach is under vary to Data Ed docent the emits of acid
gain and other a~-os~hedc polTu~n~ on Preset bees Researched must
look at not only the (ossi~i} of Crest loss/ bat also at anv decline in
He genera d~i~vesity withy Last gee sp~ies.
T~ Gaff ~~ ~ ~ ~ ~ ~=f~ {~ Deaf fag.
The Ace at which ~i~n~ven-todes are being undertaken or co~m~leted is
not Sensual With
. ,
rate at Mach the so pixel and tropical
- ~ ~ go. ~ USA ~ ~ ~'
World Forests / 35
species described during the preparation of the flora of the Rio Palenque
field station in Los Rios Province are now found only in the field station,
which covers an area of less than 1 km2 (Gentry, 1986~. Greatly improved
data on inventory are needed, particularly for tropical and subtropical
regions. A plan for developing an inventory of the world's forests must
be developed and implemented.
