(Chang was). in sweden ,, ., Wanda} hills rising only
use in (95m teen abnve the surrounding plains may
cause preclprflihun lrnin onlyl during ryelonic spells
llrontsl to be increased by steam. compared with
average tails over the lowland.“ in most countries,
however, the rain gauge net is too eoarse to detect such
small vanaoonstchorley and Betty, lm)

KEHUMIDIHCA'HON or AIRSI'KEAMS

it it rains again. uld again, the clouds that move inland
carry water mostly evaporated lrom lorests, and less
and less water evaporated lrom the sea. Forests are
eloud.rnakers both hunt water vapourevapoiated irorri
the leaves by day, arid water transpired as part or lile
processes on high islands, standing eloudi eap the
(wished peaks, but disspprar it the iorasts are eut, The
great oridging cloud that ieaehed hum the lorests ot
tdaut to the island o1 Kahoolawe, remembered by the
lathers ot the present Hawaiian settlers, has
disappared as cutting and cattle destroyed the upper
iorerts on Maui and so titted the cloud cap lrom
Kahoolawe, leaving this lower island naked to the sun
With the cloud torests gone, and the rrvers dry,
Kahoollwe is a true desert island, now used as n
bambing range (or the Air Foree.

A large evergreen tree such as :uealyptns glabulus
may pump out 3,sttod,soolnl water a day, which is
how Mussolini pumped dry the Pontme marshes oi
lraly. unthsiitty orso ol 6‘5: trees to the hedare, many
tens at thousands ot litres ot waiter are returned to the
air to beeorne clouds

A torest can return lunllluethe su) 75% ot in water to
air, n large enough anronne to loan new rain clouds.-
laayard Webster, "Forests Role in Weather Documented
in Amazon", Nero York Times iScienee Soehont, s luly
sal Forested areas return ten times as rnucti rrioisture
as hare ground, and twree as mueh as grasslands. ln
tact, as far as the atmosphere itrelt is concerned, "In:
release at water lrom trees and other plants accounts
tor halt, or even more, oI all moisture remrrted to alr.’
(Webster. ilndh This is a mural tindmg that adds even
more data to the relationship ot desertitication by
detoiestation.

It no data that no government can ignore. Drought m
one area may relate drrertly to detorestation in an
upwind diredlon. Thls study 'elearly shows that
nahnal vegetation must play an important role or the
toi-ming ot weather pamms‘ tquote lrom Thomas E
Loveioy, Viteeprtsidem ot Scienee. World wildlite
Fund)

clouds torrn above lorests, and such clouds are now
mixtures ol oceanic and lorest water vapour, clearly
di 'nglushlble by (3min rope analysis. The water
vapour horn lorests rontain more organ nucleii and
plant nutrients than does the “pore" oceanic water
mygen isotopes are measured to determine the toresh
eontribution, whlth ran bedonelor any cloud system

or the 75% oi water returned by trees to air, 25% is
evaporated trurn leat surlaees, and 50% transpired. TM

 

     

146

remaining 25th or raintall tnliltrates the soil and
eventually reaches the streams TheAmmn discharges
m. oi all rain tailing, thus the remainder is either
lostred into the torest hssue or returns to a . Moreover,
over the lorests, twttr as muzh min in"; than rs mtlnble
from the meaning MY, so that the iorest is cunlilluafly
reeyeling water to air and rain, producing an ot its
own rain (Webster, rind l. nose iindings tomer put an
end to the tallary thatoersand weatherare unrelated

Vogel (mil. applying the ‘pnndpll o1 mntimuty" oi
fluids to a tree. calculates that sap may rise, in a yoiurg
oak. rihy mm as last as the leaves transpire tneednig
only 7% ol the total trnntc area as conductive tissue,
with an actual up speed on ern/sec) it is thus certain
that only perhaps once ittieth ot the xylem is
conducting sap upwards at any one time, and that most
xylem cells eontain either air or sap at standstill, Pn-
haps too, the tree moves water up in pulsed stages
rather than as a nnrversal or eonhnuour streamtlow.

with such rapid sap flaws, however, we ran easily
imagine the water reeycled to atmosphere by a large
tree, or a slump or smaller trees,

lt is a wonder to the that we have any wateravailahle
aher we cut the lorests, or any soil There are dozens ol
case histories in modern and aneient times ot such
drslwil’loll as we lind on the Canary islands tollowmg
detorestatlon, where rivers once ran and springs
llowed. Design strategies are obvious and urgent—save
all lorest that remains, and plant trees tor increased
condensation on the hllls that lace the sea

 

Em ON SNOW AND MELWVATER
Allhnugh trees intereept some snow, the ettectotshrubs
and trees is to entiap snow at the edges otclumps, and
hold 75959. oi snowtnll in shade Melting is delayed
(or m days mmpand Wflh bare ground, so that release
ot snowmelt is a more gradual pmss ot the rrappod
snow within trees. mast is melted, while on open
ground snuw may sublime directly to air Thus. the
beneheral ettects ot trees on high slopes is not eon/need
to humid toasts, On high cold uplands such as we tind
in the conhnental rnteriors ot the Us A. or Turkey near
Mt, Ararat the thin skulls ot v-inter snnw either blow
oh the bald uplands, todrrappear in warmer air, orelse
they sublime directly to water vapour in the bright sun
0! winter. in neither case does the snow melt to
groundwater, hut is gone wflllnul productive etiect, and
no sheaths result on the lower slopes

Even a thin belt o1 trees entrapa large quantities ot
drtven snow in drihs, The result is a pmrianed release
or mettwater to river sourees in the highlands, and
shelmJlow at lower altitudes When the lorests were
cleared tor rnine timber in tins at Pyramtd Lah,
Nevada, the streams ceased to tlow, and the lake levels
tell Add to this elteet that ol rlvtl diversion and
irrigation, and whole hkes rich with hsh and wa|evlnwl
have beeorne dusttsowls, as has Latte winnemucca 1he
Cumidxka‘a Indians tl-aiuret whu lite there lost their
lash, watertowl, and treshwater in less than the years