The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1894-08-03
NATURAL RAINFALL.
DOES NATURE SLIGHT LAND IF TREES
HAVE BEEN REMoVFD2

A Problem That the Son of Columbus
started out to Solve--Many Scientists of |
various Countries Have Given the Sub
ject Much study.
A son of Christopher Columbus once un-
dertook a task of discovery that proved
much more difficult than that which his
father had tackled so successfully. In a
comparatively short time Christopher had
the solution of his problem. The answer
which his son, Fernando, set out to find is
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 it has been the
common superstition that forests increase
the rainfall within the area of their sup
posed influence, and in that way and other
ways augment Il e flow of brooks and riv-
ers. The earlier efforts to determine through
scientific methods whether there is any
good ground for the superstition were made
with appliances so crude that the margin
for error must have been considerably in
excess of the influence, if any, which the 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 "A bulletin of the forestry division
of the department of agriculture.
Water comes as near being indestructible
as any substance of which we know. Con
seuuently the total quantity of it in the
earth and in the earth's atmosphere is al
ways the same. Only very small percent
age of it is what one Of the writers in tins
bulletin terms the circulating part of the
earth's water capital. The sun makes vapor
of water that is lying at its level or Is ON
the way to find its level. This vapor is con
densed until it is heavier than the air and
starts again toward its level, and that is
bow the circulation goes on. In what way
does the presence of forests influence this
circulationi
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. A very important factor since heat
is what starts the movement of the earth :
circulating water capital is the matter OF
temperature, and the results of the investi-
cations seem to show beyond dispute that
forests reduce the maXima and the miuima
of temperature, that they reduce the maxi
ma more than the minima, and that conse
uucntly their effect is to make the average
temperature for the year cooler
Also, their mOderating influence in great
err than their cooling effect Because th'
air above forest regions Is slightly cooler
than the strata over treeless tracts, con
densation should be more rapid than ovel
open fields, and the rainfall should b,
greater These cooler bodies of air, being
blown over adjacent regions that are no
wooded should also increase somewhat tn,
precipitation there. That is the theory
and it seems to be in some degree support
ed by the measurements that have beel
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 TO
beneficial purposes. Part of it is inter
copied by foliage, and is returned to tn
atmosphere by evaporation without havin
reached the ground. The proportion so re
tanned varies with the nature of the foliage
the density of the forest and the season o
the year. The retention by evergreen orees
Is less than by deciduous 1t is estimated
that perhaps 30 per cent of the precipitation
is thus intercepted and returned to the at
mosphere. OF course this interCeption and
evaporation 90 on where the surface OF
the earth is covered by grass and Other
growing crops Whether it is sufficiently
greater in the forest than in the field to dc
away with the excess of precipitation OF
wooded tracts over that ON cleared areas il
an unsettled question.
OF the 20 per cent of rainfall which, 1t
estimated reaches the ground in forests,
part is very quickly returned to the atmos
phere by evaporation, but here the loss
considerably less than in the open field
Under certain conditions it is not more tina
Is per cent of what it would be on bare sol
but the conditions are so various that it
difficult to arrive at an average. Again, on
of this 20 per cent of precipitation whic
reaches the ground in wooded areas mu!
be deducted the loss by Transportation, ''tE
process by which the plant gets rid of I'll
surplus water after having drawn it froi
the soil in order to extract from it IL
nutriment which is present in only vel
highly attenuated solution" Various il
genious methods have been resorted to f
determining the amount of moisture ust
In this way, but because of the many ia
tors having to do with it, the amount f
the various kinds of vegetation can be 4
dictated only with a wide margin for vari
lions.
While as it stands now nobody can sa
as u result of scientific investigated
whether forests increase the fall of raj
snow or dew to an appreciabls extent, the
is no room for doubt that wooded areas a
valuable conservators of moisture. In tn
way they make the flow of streams mo
even, and they preserve the constancy
springs. In wooded areas there is loss
interception and evaporation in the fOliai
and by Transportation, and there is "A cOnsi
cradle gain in the protection from evapOr
ton from the surface of the ground. 1t
not probable that this conservation of d
water supply comes anywhere near Il
mark drawn by those who hold that Il
preservation of woodland insures an abu
dance of water supply, but the benefits I
sulting from it are sufficient to be consi
cred among the other excellent reasons f
looking well to the preservation of forest
New York Sun.
The Spanish Bull.