The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1894-02-12
NATURAL RAINFALL.
DOES NATURE SLIGHT LAND If TREES
HAVE BEEN REMOVED

- irobIem mat the son Of Columbus
started ont to Soive-Many Scientists Of
Various Countries Have Given the Sub
jeot Much study.
! son Of Christopher Columbus once un.
dertook task Of discovery that proved
much more difficult than that which his
father had tackled 10 successfully. In a
comparatively short time Christopher had
the solution of his problem. The answer
which his son, Fernando, set out 10 find IL
still missing. But the younger Columbus
thought he had discovered the true rela-
tions Of forests TO water supplies, and he
announced that the copious rainfall Of ia,
maica was produced by the islands wealth
OF forests and that the decrease Of rain in
the Azores and Canaries was because OF the
removal Of the wooded areas
/ For as long perhaps as men have given
any thought TO this matter IL has been the
common supposition that forests increase
the rainfall within the area of their sun
posed influence, and in that way and other
ways augment tie flow Of brooks and riy.
ers. The earlier efforts to determine through
scientific methods whether there is any
good ground for the supposition were made
with appliances so crude that the margin
FOR error must have been considerably in
vestigators hoped to measure In later
years efforts in the same direction have
been made with great pains, mostly IN Eu-
ropean countries, but the problem has been
found to have so many factors that, al
though the mass Of information collected
Is extremely interesting, the main question
remains practically unanswered The re-
suits of these efforts, together with some
interesting observations thereon. are set
forth in bulletin Of the forestry division
of the department Of agriculture.
Water comes as near being indestructible
as any substance of which we know Con-
sequently the total quantity of 1t In the
earth and in the earth's atmosphere is al
ways the same. Only very small percent
nge of it is what one of the writers in this
bulletin terms the circulating part OF the
earth's water capital. The sun makes vapor
Of water that is lying at it's level or is on
the way to find its level. This vapor is con.
densed until il Is heavier than the air and
starts again toward its level, and that IL
how the circulation goes on. In what way
does the presence of forests influence this
circulation?
1t would be long story to tell Of the
methods employed in France, Germany,
Sweden, Austria and other countries of Eu-
rope to measure the various influences that
must be considered in determining how and
to what extent the rainfall and the flow OF
streams are affected by the presence of for
ests very important factor since heat
Is what starts the movement Of the earth's
circulating water capital, i the matter of
temperature, and the results Of the investi-
cations seem to show beyond dispute that
forests reduce the maxima and the minima
OF temperature, that they reduce the maxi
ma more than the minima, and that conse-
quently their effect is to make the average
temperature for the year cooler.
Also, their moderating influence in great
er than their cooling effect. Because the
air above forest regions is slightly cooler
than the strata over treeess tracts, con-
densation should be more rapid than over
open fields, and the rainfall should be
greater. These cooler bodies of air being
blown over adjacent regions that are not
wooded, should also increase somewhat the
precipitation there That is the theory,
and 1t seems to be in some degree support
ed by the measurements that have been
made.
Accepting the conclusion that, in general,
forests increase slightly the fall of rain,
snow and dew, it remains to be determined
how much of this increase is available for
beneficial purposes Part of it Is inter
cepted by foliage, and is returned TO the
atmosphere by evaporation without having
reached the ground. The proportion so re-
tanned varies with the nature Of the foliase,
the density of the forest and the season Of
the year. The retention by evergreen trees
is less than by deciduous. 1t is estimated
that perhaps 80 per cent of the precipitation
is thus intercepted and returned to the at
mOsphere. OF course this interception and
evaporation go on where the surface OF
. l.. 4. =. l..
growing crops Whether it is sufficiently
greater IN the forest than in the field to do
away with the excess Of precipitation on
wooded tracts over that on cleared areas IL
an unsettled question.
OF the 20 per cent Of rainfall which, 1t is
estimated, reaches the ground in forests, a
part Is very quickly returned to the atmos-
phere by evaporation, but here the loss Is
considerably less than in the open field.
Under certain conditions IL is not more than
10 per cent of what It would be on bare soil.
but the conditions are so various that il IL
difficult to arrive AT an average. Again, out
of this 20 per cent of precipitation which
reaches the ground In wooded areas must
be deducted the loss by Transportation, the
process by which the plant gets rid Of the
surplus water after having drawn IL from
the soil in order TO extract from it the
WHICH ~ pItHtlt III bnll very
highly attenuated solution" Various in
genious methods have been resorted to for
determining the amount of moisture used
In this way, but because OF the many fac
tors having to do with it, the amount for
the various kinds of vegetation can be In
dictated only with wide margin for varia-
lions.
While as 1t stands now nobody can say,
as result of scientific investigation,
whether forests increase the fall of rain,
snow or dew to an appreciabls extent, there
Is no room for doubt that wooded areas are
valuable conservators OF moisture. In this
way they make the flow Of streams more
even, and they preserve the constaucy of
springs In wooded areas there Is loss by
lnterception and evaporation In the foliage
and by Transportation, and there is consid-
cradle gain in the protection from evapora-
ton from the surface of the ground. Ii is
not probable that this conservation of the
water supply comes anywhere near the
mark drawn by those who hold that the
preservation of woodland insIIres an album
dance of water supply, but the benefits re
/ sulting from 1t are sufficient TO be cOnsid-
cred among the other excellent reasons for
| looking well to the preservation of forests,
New York sun.