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Forest Trees (1991)

Chapter:1 World Forests

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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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Suggested Citation:"1 World Forests." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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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

22 cn au o ~ _ ~5 o o o _` o V) o - ._ - U) V) o Fin cn 5 - o o . ._ in ._ 1 LL1 ¢ c a, ¢ o o U) o o o ~ ~ ¢ a' ~ ¢ o ~ ¢ au ~ ¢ o ¢ al ~ 70 ¢ ¢ o .~ di ~ O O0 ~ ED ~ O ~ en Cal d4 co cat ~ ~ O ~ ED ~ O r) Cal O0 ~ O ~ ED ~ ~ Cal CO Go ~ o cat ~ 1 co ~ Lr) ~ ~ ~D ~ O ~ ~ ~ c~ ~ ~ ~ c~ Lr) Lo oo ~ ~ ~ ~ oo O ~D L~ Cr) C~ ~ di L~ 0 00 ~D ~ ~ L~ L~ ~ ~ O L~ O C~ O ~ ~ ~ ~ ~ ~ c~ ~ ~ ~ n ~ di ~ r~ L~ d~ ~ ~ O ~- O L~ d4 ~ ~ ~ ~ ~ ~ ~ C~ L~ O LO O ~ ~ c~ ~ ~ oO ~ ~ d~ oO O d~ oO d4 ~ oO O0 ~ ~D N E ~ ~ ~ ~ 6 =- E z ~ ° O =< cn a; o C~ ~n 5 .= ._ - o ._ ._ - C~ ._ ._ U) 50 o ._ ._ 2 - o 2 ~4 a; 5 - CD 4 ~: ·- Ct] _ CD ~ O O O _ O ,,, _ 5J ~ O =0 ~, ~ ~ ,= U ~ cn ~ O ~ ¢ cn cn cn au a; U ~ U ~ ~ X C ~ ._ ~ ._ cn ~ ~ Q ~ a; - O 2 ~ ~ O ~ ._ E~ ~ (J) oo o C~ . _ ~ ~7 · 50 :^ ._ Q O ~ U c,, · ,.c . - ._ U) ~ o ~ ._ O ~ 5 ._ _ ._ =, ¢ 2 ~ ~ O ,= O U U) ~) a; oo ~ ~ ~ ~ ~ O _ ~ ~ ~ V) ~ O _ o ,00 ,,= Z ~ ~ ~0 5 ;~ ~ O ·- ~ ~5 Q ~ ~ O ,9 E~ ~ ·- Q, U O V) J CO a' . ~ cn ~ ~ ~5 C~ - ·_ 7_ _ .~. ·- ~ U ~ _ U ¢ ~ o~ U ci, o o U ._ ~n o o ._ U) ~n ._ Q)

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

~ /: ~! 12 .., . 12 S 11 These h~o~sate!l~)tei~<ges have Chorded the eights ofthp gonst~ Con oft~he 58~364 high~^ayin Rondos, 8~. Thei/~ge on~thel~ts~h~o~s a Action of Rondos on }sly ~ 1973, data 8B>364~ppea~d.~ ash white Recoin the upper fight. Note thelakeinthelbw~rleft.D~(ka~as Spa mat ~ ~sts.The ~hitea~rea that USA ~ ~ ~ natal gushes off food , drugs, Fuel.. and fiber (Harlan ~. anal art, 1~; La~nO~ue~r' 1.945;~ Sayers, 19~a.,b; OldEeld, 19~; C. P~s~tt-^Ilen and R ~Presco~-^llen, 19~; R. ~Prescott-^J~Jen and C. Ffesco~-^]en,1983).Recenteshma~shave ~acedabouf400~esped es on the list of species that a~ endangered in whole grin significant Ha ~ Of ~ (<gene ~ ls(Food and Agdculm ~ C2~anb~hon.1985at and the 1lstls grow mg~ Pony. 1ne 1osS rate tar populations of~he same spedesis not estimable with cur~nida~ butitis expected ~ be Ocher than the loss rag Bar the spades as a Thee. with sum rapid and massiveIosses,the residence offo~est ecosystems ~ decTeased,as . ~ ~an. , .

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<h ~~ ~ under way ~ idenb~ up Aunt agents and bioche~ical~path~aysthrough ~bichsoil,~ater,andthetreesthem~ calves Airs affected ~ -~o~ll~tion. In ~r=~nv alone more than 1 000 ~ - ~ ~ ~ -->_ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ , g~e=~n~spons~dpr~edsareexamin~gthee~sof Mouton on~rests.TheExecu~veBoardoft~helLFROhasestablishedaSpeC-ia1 skFo~eonPoLubon~c~~ina~ Sea hand ~=nabononth~ problem,and~r~ev~ie~softhestateofFno~ledge~ere~ maior~partof its Todd Congress in Montreal dud Lao. AdditionalI< concern has been Using about the consequences to the ~orld's Fasts of potential y~lobaI Harming attendi~n& the dest~r~c-tion of the earth's ozone layer.

~ ~ /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<c~n~t to i~hibi~tthe s~ady~des~uch~n~f the Breast e<psy~$t~em~. .>~ e#(ibo entail b(~ij~,unde~ne#~#s~te!ms~!~br with #~herp~pu~l<!tio~ p~ssu~si~sho~ destroying dosed~!sand~open ~odland~i~nd~r~<egi~ons, :forexa~mpTeyandi~sconidbutin~to~de~rS~cation.CultivaL~ob.shiPsi~n Asiae~nco~oassl00 ~iIlio~n haan~nu~a~lJ~v, mostlvonsuchs~ho~rt~ro~tions -which at one ties that been system isthreatened.lheslash-indibu~na~gd~c~.Ttue of ~ny~pa~rts of Chid/ Asia.,a~nd Ladn Ame!dc~ ~astra~didonall~y sass tainable, but current practices heave made it another source osfloss (Fe~rsand Neue~nsch.wa~n~der,1988~.Pu~n~ de~res~dcrop~land back i~nto~production be~reessen~tialsoilnutr~tsandshucture~shavebee~n replenished also destroys potential ~restre~en.e~ration.l~n North Opera ica, far example, conversion of forests to new Crest tapes has accused over large ages when the species off ~ell~sta-b~lish~ (~climax) fasts have Ten Upland by other' pile sees Adonis dea~t~ng. Anotbercause otgen~eticlossisthe possible narrowed genetic base ~s-ulti~n~from theintensive breeding ofa ~ economically i~ortant~ spades Fadeout concern k~ con~abon. pentagons mom a ~ seduced , . The est~b~li.sh~ent ofiree individuals, far example, gives the fo~^steranopportunitytoexercise muchstri~ctercontroloverthegenetic composition ofth~e ~ ~st.Thisleadstoa progression/as ~ith~modern

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 ~<i~bie a- Id- i~me~i~ par~ts fire ,ro~i~#ayra!l<~. Thus Maine of~a~mature . ~ ~. ~. ~_ . nag toast in ~ state ~n~ls~rDe~ ~ ~nsazenal or owner noun inteiv~nio~n is cp~ye>~bop in situ, pad Me Bees fire capable of rep~du~g. Allo~og~ Carnal ~re~ne~tion to occur in the same Beast . Off ~ art ~ ~~ ~ ~ G/~ ~rf~1 of aft I. 2~r-~Z) >~ ir i~~ ~= ~ Air profit. {~ ~# JO ~ /*~s~), ^ pall {~C ~y as, ~E ~ >~1} ~ T2 ~ I. Cafe: ~ P. gaff If ~# ~ . . )~1~9'. ~ .~ he ~ ~ ~ ^ ~ In to a dies extent their sector, physic glow/ Unison/ Arm, and lid span. ^ 's genes car enable it to ron~m~ntaI con~di~dons and attacks by insects or patho~ps or to grog aster, state, lager Sneak c#~- ~. In owes and it. The sdenb~st Aced Bin the challenge ~ deadly toes that are suited to pa~c~lar news, sum as s~t~ight- ~oE~in~ Fees far l~um- ~r nut, ~ ~ ~ mat Isis the deified gene far bring pawns. lf the need is ~, edgily observable cha~ctedsS^, such as plant Boa, it is very simple to select tams with the fight genes. For He most Am, however, the Jest sdenbst selects tams ~ ~ conserved without a complete knowledge of Hat the future will I. in this challenge is to collect a ~~pre~n~ti~ sample of known and genes Such a come-on for ~ Or the seams Bus resource for that sides. From this pool, the breeder An select particular genetic Aid for direct use in production or as parents beeping Purim to develop i~mc~ved toes a , ~4 cam, the unknown ~ genetic , ~ . freak with ..

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</ ~ {~ for fling, tags drier -~m Cant a.~~l~- in thaw main Spas: On genetic v~da~bon~, ^ cony flue, and ~ul~p~i~ of ups. i~ art Base. ~ ~ in fag <~(f-~rz? 6~ r~ ~ oaf at, r~^ If ~#s~f~<s~,LeucacnaleJ~coop~h~la. Me fag ~ ~ Oaf ~ ~# Is Iffy °r ~ Amp. Chaff: U.S. ~ pf If If. ~ . space required Cedes Usual repay ductio!n is Rough Lo pollination and, genes the tams are ~en~eLcaJlv very same), out- ~ede~ (~produc~n thorough cussing of ge- neti~lly di~ffe~nt trees and, hence, the tees are ~ Icy he~~geneous)/ or ice date bug of ~ smithies to varying de . A, fit ~s~ action. Most trap sp~ies am at a very p~mit~ive stage of genetic selection front wild types compared with a~hc~ltu^1 caps, some of Bach have past Daub th~=nds ~ Bunions ~ Domesday= and up ~ a ~- Ids ~ ~ Id. \~ Me

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.

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News reports concerning decline of the world's forests are becoming sadly familiar. Most losses are measured in square kilometers, but a more profound loss cannot be measured. As forests disappear, so do their genetic resources. The genes they possess can no longer aid in their adaptation to a changing environment, nor can they be used to develop improved varieties or products.

This book assesses the status of the world's tree genetic resources and management efforts. Strategies for meeting future needs and alternatives to harvesting natural forests are presented. The book also outlines methods and technologies for management, evaluates activities now under way, and makes specific recommendations for a global strategy for forest management.

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