Introduction
Welcoming ~emarks'
James N . P i t t s , Jr.
Good morning. On behalf of D r . David Saxon,
P r e s i d e n t of t h e U n i v e r s i t y of C a l i f o r n i a , D r .
om& Rivera, Chancellor of UCR, and we of t h e
Statewide A i r P o l l u t i o n Research Center, I would
l i k e t o welcome you t o t h i s i n t e r n a t i o n a l
symposium. We t r u s t you w i l l have a s c i e n t i f i c a l l y i n t e r e s t i n g and c h a l l e n g i n g experience
during t h i s week.
The s u b j e c t of t h i s meeting i s timely and
important. The a c c u r a t e assessment of
b i o l o g i c a l , economic, and a e s t h e t i c impacts of
a i r p o l l u t a n t s on f o r e s t ecosystems i s e s s e n t i a l
i f we a r e t o develop c o s t - e f f e c t i v e c o n t r o l
s t r a t e g i e s of a i r p o l l u t i o n . Overcontrol can
l e a d t o economic p e n a l t i e s i n t h e form of e x t r a
c o s t s f o r expensive technologies f o r p o l l u t a n t
removal. On t h e o t h e r hand, undercontrol can
l e a d t o economically unacceptable p l a n t damage
which impacts n o t o n l y o u r a g r i c u l t u r a l and
f o r e s t industry but a l s o our recreational
a c t i v i t i e s . We t r u s t t h i s symposium w i l l
e l u c i d a t e a r e a s of f u t u r e r e s e a r c h t h a t w i l l
provide a more e x t e n s i v e d a t a b a s e upon which
t o g e n e r a t e r e l i a b l e models t h a t can be used f o r
such c o s t - e f f e c t i v e c o n t r o l s t r a t e g i e s .
We i n C a l i f o r n i a a r e p a r t i c u l a r l y s e n s i t i v e
t o t h e t h r e a t , indeed t h e a c t u a l i t y , of s e r i o u s
a i r p o l l u t i o n damage t o c r o p s , f o r e s t s , e t c .
A g r i c u l t u r e remains o u r number one i n d u s t r y ,
with tourism and a s s o c i a t e d r e c r e a t i o n a l
a c t i v i t i e s a l s o making a major c o n t r i b u t i o n t o
t h e economic w e l l b e i n g of o u r s t a t e .
The f a c t t h a t t h e symposium i s being h e l d
here a t UCR seems a p p r o p r i a t e s i n c e i t was a
group of p l a n t s c i e n t i s t s headed by John Middleton who, i n t h e l a t e 1940s, f i r s t showed t h a t
p l a n t damage seen in Los Angeles County was in
f a c t due t o a new type of a i r p o l l u t i o n .
p r e s e n t e d a t t h e Symposium on E f f e c t s of Air
P o l l u t a n t s on Mediterranean and Temperate
F o r e s t Ecosystems, June 22-27, 1980, R i v e r s i d e ,
C a l i f o r n i a , U.S.A.
2 ~ r o f e s s o rof Chemistry and D i r e c t o r , Statewide
A i r P o l l u t i o n Research Center, U n i v e r s i t y of
California, Riverside, California.
2
Through t h e i r e f f o r t s and t h e pioneering res e a r c h of t h e l a t e A r i e Haagen-Smit and o t h e r s ,
i t became c l e a r t h a t we were d e a l i n g w i t h an
o x i d i z i n g atmospheric system formed by t h e
a c t i o n of s u n l i g h t on hydrocarbons and o x i d e s
of n i t r o g e n .
During t h e l a s t twenty y e a r s , much of i t
under t h e l e a d e r s h i p of C l i f Taylor, r e s e a r c h
has been conducted h e r e in two major a r e a s :
S t u d i e s of p o l l u t a n t e f f e c t s on p l a n t s , vegetat i o n , and f o r e s t ecosystems, and t h e chemistry
of a i r p o l l u t i o n .
This has been a p a r t i c u l a r l y
u s e f u l combination of i n t e r e s t s because we have
one group of s c i e n t i s t s working on one a x i s of
t h e c l a s s i c dose-response curve, t h a t i s , t h e
atmospheric chemists whose f u n c t i o n i s t o
d e s c r i b e t h e dose received by man, animals, o r
p l a n t s , and a n o t h e r group working on t h e response
axis, the plant scientists investigating the
i n t e r a c t i o n s of a i r p o l l u t a n t s w i t h v e g e t a t i o n .
Most of you a r e f a m i l i a r w i t h t h e work which
has been done h e r e in t h e p l a n t s c i e n c e s a r e a .
Let me j u s t mention t h a t one of t h e major r o l e s
of t h e atmospheric chemists a t t h e Center h a s
been t h e unequivocal s p e c t r o s c o p i c i d e n t i f i c a t i o n and measurement of s e v e r a l new gaseous
oxygenated and n i t r o g e n o u s s p e c i e s t h a t a r e
formed in photochemical a i r p o l l u t i o n .
These
i n c l u d e formaldehyde, formic a c i d , n i t r i c a c i d ,
n i t r o u s a c i d , and t h e n i t r a t e r a d i c a l , NO3.
Whether o r n o t such gaseous s p e c i e s w i l l prove
t o be s i g n i f i c a n t phytotoxicants is a question
t h a t we l e a v e t o you "response" s p e c i a l i s t s .
I n c l o s i n g I want t o thank D r s . P a u l Miller
and C l i f .Taylor and M r s . Neva F r i e s e n f o r
t h e i r o u t s t a n d i n g e f f o r t s in o r g a n i z i n g t h i s
symposium. Many o t h e r people deserve a g r e a t
d e a l of c r e d i t a s w e l l , b u t t h e r e simply i s n o t
time t o acknowledge them i n d i v i d u a l l y . L e t me
j u s t s a y t h a t w e a r e p l e a s e d t o h o s t a meeting
of t h i s importance and we l o o k forward t o
l e a r n i n g of t h e s i g n i f i c a n t r e s u l t s t h a t w i l l
emerge from your g a t h e r i n g . I am c e r t a i n
t h e s e r e s u l t s w i l l be of l a s t i n g importance t o
t h i s c r i t i c a l a r e a of t h e a i r p o l l u t i o n problem.
Opening ~emarks' Robert Z. Callaham
My r e a s o n s f o r being h e r e a r e t o welcome you
on b e h a l f of t h e F o r e s t S e r v i c e , U.S. Department of
A g r i c u l t u r e , and t o i n t r o d u c e you t o t h i s conference. I want t o e x p l a i n t o you t h e o b j e c t i v e s of
t h e c o n f e r e n c e , why i t was o r g a n i z e d , and who made
i t possible.
But I a l s o want t o i n t r o d u c e you t o
each o t h e r , s o t h a t you w i l l know which c o u n t r i e s
you r e p r e s e n t , and why you a r e h e r e .
I w i l l b e g i n by s t a t i n g t h e t h r e e object i v e s of t h i s c o n f e r e n c e . The f i r s t i s t o review
c u r r e n t i n f o r m a t i o n on s p e c i f i c gaseous and p a r t i c u l a t e p o l l u t a n t s and t h e i r e f f e c t s on f o r e s t ecosystems. F o r e s t s a s s o u r c e s of p o l l u t a n t s and a s
s i n k s f o r p o l l u t a n t s a r e i n c l u d e d . The second
o b j e c t i v e i s t o a n a l y z e primary, secondary, and
i n t e r a c t i v e e f f e c t s of c h r o n i c p o l l u t a n t s on
ecosystems. Modeling w i l l b e explored a s a t o o l t o
s i m u l a t e observed and expected e f f e c t s . L a t e i n
t h e program, s t r a t e g i e s f o r a s s e s s i n g and managing
environmental impacts of a i r p o l l u t a n t s w i l l b e
d i s c u s s e d . The t h i r d o b j e c t i v e i s t o s t i m u l a t e
i n t e r n a t i o n a l communication t o a s s e s s t h e s t a t e of
knowledge and t o i d e n t i f y gaps i n our knowledge.
S e v e r a l y e a r s ago, t h e U.S. Environmental
P r o t e c t i o n Agency (EPA) gave a g r a n t f o r r e s e a r c h
t o D r . C l i f Taylor i n t h e Statewide A i r P o l l u t i o n
Center h e r e a t R i v e r s i d e . The F o r e s t S e r v i c e h a s
a c t i v e l y c o o p e r a t e d and p a r t i c i p a t e d i n t h e r e s u l t i n g r e s e a r c h up t o t h e p r e s e n t time. Research
under t h a t g r a n t i s drawing t o a c l o s e . T h i s conf e r e n c e was planned, t h e r e f o r e , t o sum up what h a s
been accomplished. S c i e n t i s t s involved i n t h i s
m u l t i m i l l i o n d o l l a r r e s e a r c h e f f o r t have t h i s
o p p o r t u n i t y t o t e l l o t h e r s what t h e y have l e a r n e d
1
P r e s e n t e d a t t h e Symposium on E f f e c t s of
A i r P o l l u t a n t s on Mediterranean and Temperate
F o r e s t Ecosystems, J u n e 22-27, 1980,
R i v e r s i d e , C a l i f o r n i a , U.S.A.
D i r e c t o r , P a c i f i c Southwest F o r e s t and Range
Experiment S t a t i o n , F o r e s t S e r v i c e , U.S.Department
of A g r i c u l t u r e , Berkeley, C a l i f o r n i a .
2
and t o i d e n t i f y problems t h a t remain t o b e s o l v e d .
Another purpose i n o r g a n i z i n g t h i s c o n f e r e n c e i s
t o broaden l o c a l p e r s p e c t i v e s by importing e x p e r t s
from around t h e world t o t a l k about o u r problems.
The f i n a l purpose i s t o t r a n s f e r technology gene r a t e d by t h i s r e s e a r c h program t o t h e managers of
a i r , l a n d , and f o r e s t r e s o u r c e s .
T h i s c o n f e r e n c e was made p o s s i b l e through t h e
c o o p e r a t i v e e f f o r t s of s e v e r a l a g e n c i e s . The
F o r e s t S e r v i c e , U.S. Department of A g r i c u l t u r e ,
and t h e S t a t e w i d e A i r P o l l u t i o n Research C e n t e r ,
U n i v e r s i t y of C a l i f o r n i a , a t R i v e r s i d e , a r e spons o r s . IUFRO, t h e I n t e r n a t i o n a l Union of F o r e s t r y
Research O r g a n i z a t i o n s , having about 380 member
o r g a n i z a t i o n s i n 86 c o u n t r i e s around t h e world and
a s u b j e c t group concerned w i t h a i r p o l l u t i o n , i s a
cosponsor. The U.S. Department of Energy and t h e
U.S. Environmental P r o t e c t i o n Agency have made
t h e i r p e o p l e and t h e i r r e s o u r c e s a v a i l a b l e . EPA
w i l l h e l p t h e F o r e s t S e r v i c e t o p u b l i s h t h e proceedings. The U.S. Department of S t a t e , p a r t i c u l a r l y t h e Man and t h e Biosphere Program through
i t s P r o j e c t 2 ~ M e d i t e r r a n e a nand Temperate F o r e s t
Ecosystems--has provided f i n a n c i a l s u p p o r t .
UNESCO, t h e i n t e r n a t i o n a l home of t h e Man and t h e
Biosphere Program, h a s p a i d t o b r i n g t h r e e i n t e r n a t i o n a l p a r t i c i p a n t s h e r e . For a l l of t h i s supp o r t and c o o p e r a t i o n , t h e o r g a n i z e r s a r e most
gratef ul.
My f i n a l and, perhaps, unexpected r e a s o n f o r
being h e r e i s t o i n t r o d u c e you t o each o t h e r .
Although t h i s i s n o t o f t e n done a t c o n f e r e n c e s , I
have found i t t o b e a n e f f e c t i v e means of stimul a t i n g communication. I am going t o c a l l t h e r o l l
of c o u n t r i e s , more o r l e s s i n a l p h a b e t i c a l o r d e r .
and a s k t h e i n d i v i d u a l s named t o s t a n d .
(Introd u c t i o n s followed.) About 20 p e r c e n t of t h e
people h e r e a r e from o u t s i d e North America. L e t
u s g i v e t h e s e v i s i t o r s a s p e c i a l welcome. Walk up
t o them. I n t r o d u c e y o u r s e l v e s . Ask t h e s e v i s i t o r s about programs and problems i n t h e i r
countries.
Now t h a t we know what c o u n t r i e s a r e r e p r e s e n t e d ,
l e t me c a l l f o r a show of hands t o f i n d o u t why
130 of you a r e h e r e . How many a r e p r i m a r i l y
t e a c h e r s o r p r o f e s s o r s ? About 7 p e r c e n t . How
many a r e managers of l a n d o r f o r e s t r e s o u r c e s ?
About 9 p e r c e n t . How many a r e managers of a i r resources? Only a b o u t 2 p e r c e n t . That i s s u r p r i s ing. How many of you a r e s t u d e n t s , n o t y e t i n t o
p r o f e s s i o n a l a c t i v i t i e s ? About 2 p e r c e n t . The
remainder of y o u ~ a b o u t80 p e r c e n t ~ a r es c i e n t i s t s
and i n v e s t i g a t o r s . That i s a b o u t what I expected.
And now my r o l e i s f u l f i l l e d . I have
i n t r o d u c e d you t o t h e c o n f e r e n c e and t o each o t h e r .
I e x p e c t you t o b e n e f i t b o t h p r o f e s s i o n a l l y and
p e r s o n a l l y from t h i s c o n f e r e n c e . L a s t l y , I
e x p r e s s my deep a p p r e c i a t i o n t o a l l who have cont r i b u t e d t o t h e o r g a n i z a t i o n of t h i s c o n f e r e n c e
and p a r t i c u l a r l y t o Dr. P a u l M i l l e r .
On b e h a l f of t h e F o r e s t S e r v i c e , I t h a n k you
f o r coming. The u l t i m a t e s u c c e s s and meaning of
t h i s c o n f e r e n c e depend on you.
Air Pollution in Forests: Social Costs,
Predictive Models, and Public ~ o l i c y '
C h a r l e s F. Cooper 2
A b s t r a c t : Long t i m e s c a l e s , s p a t i a l v a r i a t i o n i n ecosystems, and d i f f e r i n g v a l u e judgments make
models almost e s s e n t i a l f o r s o c i e t a l consensus about a i r p o l l u t i o n .
Three c a t e g o r i e s of
p o l i c y - o r i e n t e d models a r e d e s c r i b e d .
Empirical time s e r i e s models a r e good f o r immediate
d e c i s i o n s but a r e i n h e r e n t l y a short-term
device.
D e t a i l e d s t r u c t u r a l - f u n c t i o n a l models
emphasize r e l a t i o n s h i p s among components and demonstrate t h e s i g n i f i c a n c e of i n t e r c o n n e c t i o n s .
Small e r r o r s , however, can l e a d t o e r r o n e o u s q u a n t i t a t i v e r e s u l t s , l i m i t i n g t h e i r v a l u e f o r
direct policy decisions.
Aggregated p o l i c y - o r i e n t e d models p r o v i d e b e t t e r compliance between
model o u t p u t and v a l i d a t i o n d a t a a t t h e c o s t of l o s s of r e s o l u t i o n .
Good models should be
c l e a r l y documented, r e s u l t s s h o u l d be comprehensible, l i m i t s and probable e r r o r bands c l e a r l y
s t a t e d , t h e y should be f l e x i b l e enough t o d e a l with u n a n t i c i p a t e d problems without a t t e m p t i n g
t o t a l g e n e r a l i t y , and r e s u l t s should be c l e a r l y d i s p l a y e d . A model is a n a i d t o decisionmaking,
not a d e c i s i o n maker.
For i t t o be e f f e c t i v e i n t h a t r o l e , t h e r e must be mutually s u p p o r t i v e
i n t e r a c t i o n among modelers, b i o l o g i c a l and s o c i a l s c i e n t i s t s , and d e c i s i o n makers. Perhaps t h e
most s i g n i f i c a n t r o l e of models i s i n h e l p i n g t o avoid s u b o p t i m i z a t i o n and i n f a c i l i t a t i n g
communication among d i s c i p l i n e s and p r a c t i t i o n e r s .
Atmospheric p o l l u t i o n i s a f f e c t i n g f o r e s t
ecosystems i n much of t h e world.
A major purpose
of t h i s symposium is t o e s t a b l i s h a s c i e n t i f i c
consensus about t h e n a t u r e , magnitude, and t i m e
t r e n d of t h e s e e f f e c t s .
A scientific resolution,
however, is n o t enough. A n a l y s i s of "The E f f e c t s
of A i r P o l l u t a n t s on Mediterranean and Temperate
Forest
Ecosystems"
must
also
take
societal
o b j e c t i v e s and l i m i t a t i o n s i n t o a c c o u n t .
Ecosystems used and enjoyed by man a r e
embedded i n a l a r g e r s o c i a l system; d e a l i n g w i t h
e f f e c t s of a i r p o l l u t i o n on t h e s e ecosystems,
l o c a l l y , r e g i o n a l l y , o r g l o b a l l y , t h u s becomes a
q u e s t i o n of p u b l i c p o l i c y .
E s s e n t i a l t o sound
p u b l i c p o l i c y f o r m u l a t i o n is knowledge of t h e
s o c i a l c o s t s of a i r p o l l u t i o n and i t s c o n t r o l . A
m a j o r problem, of c o u r s e , i s how t o measure t h e s e
costs.
T h i s symposium should l e a d u s some way
toward b e t t e r assessment of t h e r e a l c o s t s of
forest a i r pollution.
p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r
P o l l u t a n t s o n M e d i t e r r a n e a n and Temperate F o r e s t
Ecosystems, J u n e 22-27, 1980, R i v e r s i d e , C a l i f o r n i a , U.S.A.
2 ~ r o f e s s o rof Biology and D i r e c t o r of C e n t e r f o r
Regional Environmental S t u d i e s , San Diego S t a t e
University, SanDiego, California
92182.
The e c o l o g i c a l and s o c i a l consequences of a i r
p o l l u t i o n i n f o r e s t s a r e t h e r e s u l t of complex
i n t e r a c t i o n s of
p r o c e s s e s w i t h many t e m p o r a l ,
s p a t i a l , and v a l u e s c a l e s .
Long-t ime s c a l e s ,
v a r i a t i o n s among ecosystems, and d i f f e r e n c e s of
o p i n i o n about v a l u e s make c l a s s i c a l l a b o r a t o r y
e x p e r i m e n t a t i o n almost u s e l e s s f o r d e f i n i n g t h e s e
large
scale
consequences.
Models
are
thus
e s s e n t i a l f o r helping t o a r r i v e a t a s o c i e t a l
consensus about how t o t r e a t a i r p o l l u t i o n .
COMPLEXITY OF THE FOREST AIR POLLUTION PROBLEM
It i s a t r u i s m t h a t t h e f o r e s t a i r
is complex,
but t h e n a t u r e
problem
complexity must
be understood i f we
v i s u a l i z e t h e r o l e of models i n d e a l i n g
The p o i n t s mentioned h e r e a r e e l a b o r a t e d
a u t h o r s i n t h i s volume.
pollution
of
that
are t o
with i t .
by o t h e r
Air
pollution
affects
individual
plants
d i r e c t l y , i n ways which change d u r i n g t h e c o u r s e of
the plant's
l i f e history.
It a f f e c t s p l a n t s
i n d i r e c t 1y,
through
impacts on s o i l s and on
consumers and decomposers.
E f f e c t s on p l a n t s , i n
turn, a r e reflected i n other trophic levels.
C r i t i c a l l y important i s t h e dynamic r e a c t i o n of
ecosystems, which u s u a l l y cannot be p r e d i c t e d from
a simple summation of t h e r e s p o n s e s of i n d i v i d u a l
organisms
.
Social
consequences
stem
from
p r o d u c t i v e r e s o u r c e s and amenity v a l u e s .
loss
of
Wood and
forage growth may d i m i n i s h , a l o s s t h a t w i l l be
increasingly s i g n i f i c a n t i f f o r e s t s a r e i n greater
demand f o r biomass a s a s o u r c e of energy o r
s t r u c t u r e d chemicals, o r i f i n c r e a s i n g need f o r
g r a i n a s food l e a d s t o more p r e s s u r e on rangelands.
A e s t h e t i c and r e c r e a t i o n a l v a l u e s a r e l o s t .
The
degraded appearance of t h e smog-affected f o r e s t s of
t h e San Gabriel Mountains a r e apparent t o a l l who
have seen them. W i l d l i f e , both game and non-game,
may s u f f e r .
Lakes and s t r e a m s i n s e v e r a l p a r t s of
North America and Europe have l o s t much of t h e i r
c a p a c i t y f o r f i s h production (Loucks 1980).
Of
course,
there
may
be
beneficial
impacts a s
well--a1 l e v i a t i o n of l o c a l s u l f u r d e f i c i e n c i e s , f o r
instance.
Both b e n e f i c i a l and d e t r i m e n t a l e f f e c t s
vary i n t i m e and s p a c e .
A i r p o l l u t i o n o p e r a t e s a t many time s c a l e s .
Hol l i n g (1973) h a s d i s t i n g u i s h e d between f a s t and
slow v a r i a b l e s .
Fast variables a r e generally
amenable
to
conventional
laboratory
e x p e r i m e n t a t i o n , and a r e t h e kind t h a t a r e u s u a l l y
studied i n biological research.
Slow v a r i a b l e s ,
however, t a k e long enough t o m a n i f e s t themselves
that controlled experimentation is impractical i n
many r e a l world s i t u a t i o n s where a c t i o n cannot
wait.
Decision makers must a l s o d e a l with a high
degree of s p a t i a l h e t e r o g e n e i t y i n both p o l l u t a n t s
and t h e i r t a r g e t ecosystems.
Theory and r e s e a r c h
i n ecology h a s n o t u n t i l now d e a l t very well with
s p a t i a l processes.
F i n a l l y , a i r p o l l u t i o n i s o n l y one of many
stresses a f f e c t i n g f o r e s t ecosystems.
Multiple
s t r e s s e s may i n t e r a c t s y n e r g i s t i c a l l y o r they may
h e l p t o c o u n t e r a c t one a n o t h e r .
We need t o know
more, f o r i n s t a n c e , about t h e combined impact of
a i r p o l l u t i o n and c l i m a t e change, whether due t o
d e l i b e r a t e weather m o d i f i c a t i o n o r i n a d v e r t e n t
c l i m a t i c change.
Increased atmospheric carbon
d i o x i d e from burning of f o s s i l f u e l seems l i k e l y t o
warm t h e e a r t h ' s c l i m a t e and, perhaps, t o s t i m u l a t e
p l a n t growth d i r e c t l y .
How w i l l t h e s e p r o c e s s e s
i n t e r a c t with a i r p o l l u t a n t s ? F o r e s t h a r v e s t and
r e g e n e r a t i o n is i t s e l f a s t r e s s on t h e ecosystem
i n t e r a c t with
increased
pollutant
which w i l l
l o a d i n g . A i r p o l l u t i o n i n f o r e s t s t h u s i s p a r t of
a
complex
network
of
biological
and
social
i n t e r a c t i o n s whose i n t e g r a t e d impacts a r e almost
impossible
to
untangle
through
single-factor
analysis.
A SCIENTIFIC APPROACH TO COMPLEXITY
There
are
some
four
possible
societal
responses
to
complex
problems
such
as
air
pollution.
We can a t t e m p t t o t r e a t t h e symptoms
through such means a s f e r t i l i z a t i o n o r i r r i g a t i o n ,
a l l e v i a t e t h e cause through emission c o n t r o l ,
accept t h e degradation a s gracefully a s possible,
o r c o n v e r t t h e a f f e c t e d ecosystem t o one more
r e s i s t a n t t o s t r e s s . Actual p o l i c y s o l u t i o n s will
probably i n c l u d e some combination of t h e s e .
How do we go about choosing the- a p p r o p r i a t e
p o l i c y response? One way i s simply t o r e l y on t h e
judgment, h o p e f u l l y good, of t h e people, hopeful 1 y
experienced,
i n charge.
T h i s Is t h e common
procedure.
There is, however, a more organized
s c i e n t i f i c approach t o complex problems with many
temporal and s p a t i a l s c a l e s . T h i s process i n c l u d e s
eight basic s t e p s
.
1. Make
a model of t h e p r o c e s s , based on
e x i s t i n g knowledge and understanding of t h e
system.
The k i n d s of model which might be
undertaken i n t h i s s t e p a r e d i s c u s s e d i n more
d e t a i l below.
2. F i t t h e parameters of t h e model t o d a t a ,
p r e f e r a b l y obtained from l a b o r a t o r y o r f i e l d
experimentation; o t h e r w i s e from o b s e r v a t i o n a l
studies
.
3 . V a l i d a t e t h e model.
T h i s i n v o l v e s comparison
of model r e s u l t s with r e a l world outcomes i n
systems o t h e r t h a n t h o s e used i n f i t t i n g t h e
parameters.
T h i s is a c r u c i a l but a l s o a
most d i f f i c u l t s t e p , because t h e o b j e c t i v e of
t h e whole modeling e x e r c i s e i s o f t e n t o
p r e d i c t r e s p o n s e s of systems under s t r e s s e s
t h a t exceed t h e r a n g e of e x i s t i n g v a l i d a t i o n
data.
4. Test
the
sensitivity
of
t h e model
to
parameter changes.
T h i s can h e l p t o l o c a t e
c r i t i c a l f e a t u r e s where b e t t e r understanding
It can
o r more a c c u r a t e d a t a a r e needed.
a l s o h e l p l o c a t e p a r t s of t h e system where
r e l a t i v e l y small changes may have l a r g e
effects.
S e n s i t i v i t y a n a l y s i s is o f t e n s a i d
t o be one of t h e g r e a t v i r t u e s of a modeling
approach, i n t h a t i t l e a d s t o d i r e c t i n g
l i m i t e d r e s o u r c e s t o a r e a s where t h e y w i l l do
t h e most good, o r c o n v e r s e l y a v o i d s t h e
e x p e n d i t u r e of e f f o r t on measures u n l i k e l y t o
have
much
effect.
Points
of
special
s e n s i t i v i t y a r e of t e n hard to f i n d , however.
Both c o n t r o l theory and p r a c t i c a l e x p e r i e n c e
a r e i n c r e a s i n g l y demonstrating t h a t many
complex i n t e r 1 inked systems a r e r e l a t i v e 1 y
i n s e n s i t i v e t o small changes i n one o r two
variables.
T h i s should come a s no s u r p r i s e
t o t h o s e who have observed t h e e v i d e n t
resilience
of
ecosystems
under
stress
(Holling
1973).
Sensitivity
analysis
remains,
nevertheless,
an
important
a p p l i c a t i o n of p o l i c y - o r i e n t e d models.
5. Use t h e model o u t s i d e t h e r a n g e s of s t r e s s e s
p r e v i o u s l y experienced.
One of t h e p i t f a l l s
t h a t a l l of us have been warned t o avoid i n
s c i e n c e i s e x t r a p o l a t i o n , yet i t is j u s t
because of t h e need f o r e x t r a p o l a t i o n t h a t
models a r e c a l l e d f o r i n p r e d i c t i n g ecosystem
consequences of a i r p o l l u t i o n . The response
of t h e model system w i l l u s u a l l y need t o be
e s t i m a t e d under p o l l u t i o n l o a d s g r e a t e r t h a n
t h o s e a l r e a d y experienced by t h a t system.
Even more important i s t h e time dimension. A
primary goal o f t e n i s assessment of t h e
long-term consequences of c h r o n i c o r e p i s o d i c
a i r p o l l u t i o n . It is j u s t because of t h i s
extended t i m e dimension t h a t models a r e
needed, and yet t h i s is perhaps t h e most
d i f f i c u l t element i n t h e i r c o n s t r u c t i o n .
6. Array t h e output f o r p u b l i c d i s c u s s i o n .
S i n c e t h e purpose of t h e models we a r e
c o n s i d e r i n g h e r e is t o h e l p i n a r r i v i n g a t
some s o r t of consensus about a p p r o p r i a t e
societal
response,
p r e s e n t a t i o n must
go
beyond t h e immediate s c i e n t i f i c community.
Seldom,
if
e v e r , w i l l t h e output of a
realistic
air
p o l l u t i o n model
lead
to
deterministic
predictions.
Rather, t h e r e
w i l l be a range of a l t e r n a t i v e outcomes, each
It i s
with a p r o b a b i l i t y l e v e l a t t a c h e d .
notoriously
difficult
to interpret
risk
p r o b a b i l i t i e s i n terms of p u b l i c a t t i t u d e s .
is
a
growing
literature
on
There
p r o b a b i l i s t i c r i s k assessment which i s h i g h l y
p e r t i n e n t t o t h e a i r p o l l u t i o n problem (e.g.,
Kates 1978, S t a r r and Whipple 1980).
7. Amalgamate with output of o t h e r r e l e v a n t
models of s o c i e t a l i s s u e s f o r f i n a l p u b l i c
evaluation.
A i r p o l l u t i o n i s only one of
many problems f a c i n g s o c i e t y . Measures t a k e n
to
alleviate
the
consequences
of
air
p o l l u t i o n a r e l i k e l y t o ramify i n t o many
o t h e r a s p e c t s of s o c i e t y .
I n my view, t h e
most
important
single
use
of
a
policy-oriented
model
is a s an a i d i n
avoiding suboptimization.
By subopt imizat i o n , of c o u r s e , i s meant choosing what is
c l e a r l y and l o g i c a l l y t h e best s o l u t i o n t o a
s m a l l p a r t of a problem without adequately
c o n s i d e r i n g t h e impact of t h a t s o l u t i o n on
the
total
system.
An example of
how
s u b o p t i m i z a t i o n along a narrow path may t u r n
o u t t o be n o t j u s t s l i g h t l y wrong, but
e x a c t l y wrong i n a broader c o n t e x t is t h e
d i s p o s a l of chemical wastes a t Love Canal,
N. Y.
Out-of - s i g h t , out-of -mind b u r i a l was a
good s o l u t i o n a t t h e time f o r t h e p o t e n t i a l
hazard t o workers and t h e p u b l i c of t h i s
m a t e r i a l ; i t s consequences a r e now a f f e c t i n g
a l l Americans, a s t a x p a y e r s , i f not a s
r e c i p i e n t s of d i r e c t chemical i n s u l t .
Less
extreme c a s e s of s u b o p t i m i z a t i o n may be more
d i f f i c u l t t o i d e n t i f y b e f o r e a c t i o n is taken.
I f a p r o p e r l y designed model, by e x p l o r i n g a
w i d e r range of a l t e r n a t i v e s t h a n can t h e
human mind
alone,
h e l p s t o avoid t h e
long-term
costs
of
suboptimization,
the
e f f o r t i n i t s c o n s t r u c t i o n w i l l be well
rewarded.
8. Move toward a d e c i s i o n .
There is no hope
t h a t a d e c i s i o n , even i f based on t h e best
conceivable
model,
will
satisfy
all
interested p a r t i e s i n a controversial issue.
One c o u l d e x p e c t , however, t h a t t h e d e c i s i o n
would be more r a t i o n a l t h a n i f based on
emotion
and
maximization
of
each
participating
individual's
personal
objectives.
KINDS OF POLICY-ORIENTED MODELS
Models may be merely conceptual and verbal--an
i n t u i t i v e , possibly q u i t e accurate, v i s u a l i z a t i o n
of how t h e world works.
We a r e concerned h e r e ,
however, with mathematical models a b l e t o d e a l with
i n t e r a c t i o n s among more v a r i a b l e s t h a n t h e unaided
human mind can r e a d i l y handle.
These a r e of
s e v e r a l b a s i c kinds, which d i f f e r i n both t h e i r
underlying
structure
and
their
range
of
application.
(This
section
owes
much
to
R.
Emanuel , Environmental
d i s c u s s i o n s with W.
Sciences D i v i s i o n , Oak Ridge National L a b o r a t o r y . )
1. Empirical time series a n a l y s i s . The emphasis
h e r e i s on a n a l y s i s of t h e s e c u l a r t r e n d of
It i s assumed
t h e v a r i a b l e s of i n t e r e s t .
t h a t t h e processes d u r i n g t h e period of
record w i l l c o n t i n u e over t h e i n t e r v a l of
extrapolation.
A time s e r i e s model need not
It
include e x p l i c i t casual relationships.
must, however, i n c o r p o r a t e s u f f i c i e n t d a t a t o
e s t a b l i s h t h e s t a t i s t i c a l s i g n i f i c a n c e of t h e
observed p a t t e r n s .
I n t h e words of Dennis
Meadows (1975), i t i s "data r i c h , t h e o r y
poor. "
Such a time s e r i e s a n a l y s i s is o f t e n i d e a l
f o r d e c i s i o n s which must be made immediately
but which can be revoked i n t h e l i g h t of new
information
without
lasting
damage,
biological,
or
political.
Time
series
a n a l y s i s h a s t h e advantage t h a t i t i s e a s i l y
understood by d e c i s i o n makers who a r e not
It i s i n h e r e n t l y a
analytically inclined.
short-term t o o l , however.
Lack of e x p l i c i t
c a s u a l r e l a t i o n s h i p s makes e x t r a p o l a t i o n even
more r i s k y t h a n with o t h e r models.
2. D e t a i l e d s t r u c t u r a l - f u n c t i o n a l models. These
i n c o r p o r a t e t h e s t r u c t u r e and f u n c t i o n of t h e
system t o t h e e x t e n t t h a t it is known. There
i s a wide v a r i e t y of suggested procedures and
approaches f o r c o n s t r u c t i n g such models;
s e v e r a l a r e discussed i n t h i s volume.
The
i s on u n d e r s t a n d i n g
emphasis throughout
r e l a t i o n s h i p s and p r o c e s s e s , n o t t r e n d s .
In
Meadows' (1975) words, t h e y a r e "theory r i c h ,
d a t a poor."
T h e i r p r i n c i p a l v a l u e i s a s an a i d t o
understanding r e l a t i o n s h i p s among components
and t h e s i g n i f i c a n c e of I n t e r c o n n e c t i o n s .
They a r e o f t e n u s e f u l f o r p o i n t i n g out t o
d e c i s i o n makers why c e r t a i n r e l a t i o n s h i p s
whose importance is not i n t u i t i v e l y obvious
a r e a c t u a l l y more s i g n i f i c a n t t h a n they seem.
Proper1 y c o n s t r u c t e d f u n c t i o n a l models can
l e a d t o p r e d i c t i o n of ecosystem r e s p o n s e s t o
s t r e s s e s , which a r e l i k e l y t o d i f f e r markedly
from t h o s e of i n d i v i d u a l organisms t e s t e d i n
isolation.
West and o t h e r s (1980) used a
model of s u c c e s s i o n a l dynamics t o t e s t t h e
long-term impact of a i r p o l l u t i o n on e a s t e r n
deciduous f o r e s t s .
T h e i r model p r e d i c t e d
enhanced growth of
some s p e c i e s d e s p i t e
p o l l u t a n t stress, s i n c e they may g a i n a
c o m p e t i t i v e advantage because they a r e l e s s
s e n s i t i v e t h a n o t h e r s p e c i e s with which t h e y
i n t e r a c t i n t h e s u c c e s s i o n a l process.
Neither e c o l o g i c a l models, nor e c o l o g i c a l
t h e o r y i n g e n e r a l , d e a l well with s p a t i a l
dynamics i n f o r e s t s . Most emphasis h a s been
on s u c c e s s i o n a l dynamics over time a t a p o i n t
o r i n a small a r e a .
There have been
a t t e m p t s , a s by Shugart and o t h e r s (1973) t o
model t h e "flow" of one form of land use o r
v e g e t a t i o n c o n d i t i o n t o a n o t h e r , but t h i s
approach is c h i e f l y u s a b l e f o r very l a r g e
units.
Because
air
pollution
i s both
s p a t i a l l y extended and s p a t i a l l y v a r i a b l e ,
t h e r e is a need t o i n c o r p o r a t e t h e s e f e a t u r e s
i n t o e c o l o g i c a l models of a i r p o l l u t i o n .
A
promising approach seems t o be t h e l i n k i n g of
existing
forest
succession
models
with
c a r t o g r a p h i c models developed by geographers
f o r dynamic map a n a l y s i s . E f f o r t s t o do t h i s
a r e now underway i n s e v e r a l r e s e a r c h u n i t s .
The r e s u l t s should be v a l u a b l e f o r a i r
pollution studies.
D e s p i t e t h e i r g r e a t v a l u e f o r many purposes,
however,
detailed
structural-functional
models a r e u s u a l l y u n s u i t a b l e f o r d e c i d i n g
upon s p e c i f i c a c t i o n s o r p o l i c i e s .
Small
e r r o r s , e i t h e r i n t h e o r e t i c a l underpinnings
o r i n parameter e s t i m a t i o n , can l e a d t o
q u a n t i t a t i v e p r e d i c t i o n s t h a t t u r n out t o be
q u i t e wrong when t e s t e d a g a i n s t t h e l i m i t e d
validation data usually available.
We can
hope,
though,
that
improvement
i n both
modeling t e c h n i q u e and i n b i o l o g i c a l and
s o c i a l knowledge w i l l l e a d t o f u n c t i o n a l
models t r u l y u s e f u l
a s decision tools.
3. Aggregated pol icy-orient ed models.
Here,
t h e r e i s a n attempt t o combine t h e many
s t r u c t u r a l elements of t h e system i n t o a
r e l a t i v e 1 y few we1 1-understood components f o r
which good cause and e f f e c t d a t a e x i s t . The
major s t r u c t u r a l and f u n c t i o n a l r e l a t i o n s h i p s
a r e preserved,
but a t a lower l e v e l of
resolution
with
respect
to
their
interconnections.
F u l l understanding of t h e
complex
system
is
traded
for
greater
computational t r a c t a b i l i t y , and a g r e a t e r
p o s s i b i l i t y of showing time s e r i e s d a t a .
With t h i s s o r t of model i n hand, s c i e n t i s t s
c a n i n t e r a c t w i t h d e c i s i o n makers i n a
q u a n t i t a t i v e way t o prepare an a r r a y of
alternative
actions
and
their
probable
consequences. Various t o o l s of o p t i m i z a t i o n ,
a n a c t i v e a r e a of c u r r e n t r e s e a r c h , come i n t o
play h e r e .
Particularly valuable i n a
problem with a s many c o n f l i c t i n g v a l u e
judgments a s e f f e c t s of a i r p o l l u t i o n may be
the
multiple
objective
optimization
e x t e n s i v e l y used i n e v a l u a t i n g water r e s o u r c e
development a l t e r n a t i v e s (Cohon and Marks
1975).
T h i s i s a planning concept which
provides a q u a n t i t a t i v e framework f o r t h e
t a s k faced by a l l d e c i s i o n makers, t h a t of
achieving an a c c e p t a b l e compromise among a
s e t of competing o b j e c t i v e f u n c t i o n s .
The
v a r i o u s a n a l y t i c a l techniques used f o r t h i s
purpose a g r e e i n using t h e model t o o f f e r
tradeoff
f u n c t i o n s of some kind t o t h e
d e c i s i o n maker. But h e , not t h e model o r t h e
modeler, e s t a b l i s h e s p r i o r i t i e s among t h e
planning c r i t e r i a .
The model is t h u s j u s t
one more t o o l f o r bringing p r e c i s i o n i n t o t h e
planning process and f o r e v a l u a t i n g t h e
consequences of a l t e r n a t i v e c h o i c e s .
be
Ecological
policy
models
would
s u b s t a n t i a l l y improved i f t h e y could d i r e c t l y
i n c o r p o r a t e human d e c i s i o n making i n response t o
ecosystem change.
A c t i v e r e s e a r c h is i n p r o g r e s s
t o make t h i s p o s s i b l e .
For i n s t a n c e , C. L. Smith,
J.
M.
Stander,
and
A.
V.
Tyler
(personal
communication 1980), of Oregon S t a t e U n i v e r s i t y , a n
anthropologist,
an ecosystem modeler,
and
a
fisheries
biologist,
have
collaborated
in
developing an i n t e r a c t i v e model of a mythical human
h u n t i n g and g a t h e r i n g s o c i e t y and an e x p l o i t e d
fishery.
Human
participants
are
faced
with
a l t e r n a t i v e s which f o r c e them t o make c h o i c e s . The
consequences of t h e c h o i c e s a r e t h e n e v a l u a t e d by
t h e models i n accordance with previous1 y developed
d e c i s i o n r u l e s . They found t h a t d e c i s i o n making i n
simulations
did
alter
model
outcomes.
Decisionmaking i n t h e f i s h e r y s i m u l a t i o n l e d t o a
s t a b l e e q u i l i b r i u m ; without i t , t h e r e was p e r i o d i c
c y c l i n g of f i s h i n g v e s s e l s and f i s h biomass. Wrong
decisions,
though,
l e d t o extinction-economic
e x t i n c t i o n of
the
fishery
before
biological
e x t i n c t i o n of
the fish.
Similar i n t e r a c t i v e
modeling i d e a s a r e being developed by H o l l i n g
(1978) and h i s a s s o c i a t e s and f o l l o w e r s under t h e
r u b r i c of Adaptive Environment Assessment.
DESIRABLE CHARACTERISTICS OF MODELS
To be e f f e c t i v e t o o l s f o r a s s i s t i n g i n p o l i c y
decisions,
models
should
have
several
It
i s almost
characteristics
(Cooper 1976).
t o t a l l y i r r e l e v a n t i n t h i s c o n t e x t whether t h e
model uses d i f f e r e n t i a l o r d i f f e r e n c e e q u a t i o n s o r
whether i t i s w r i t t e n i n FORTRAN o r BASIC. There
a r e more fundamental f e a t u r e s which determine
whether a model i s l i k e l y t o be accepted and used
i n decisionmaking.
1. It
should
be
extensively
and
clearly
documented. How was t h e model developed and
T h i s should be
what a r e i t s assumptions?
e v i d e n t , i f not t o t h e u l t i m a t e u s e r , a t
l e a s t t o t h o s e who might s e r v e a s t e c h n i c a l
consultants.
Unfortunately,
this
is
a
s e r i o u s weakness of most models. T h i s a r i s e s
p a r t l y from funding limitations--documentst i o n i s an obvious t h i n g t o skimp i f t h e
budget h a s t o be c u t .
I suspect t h a t not
i n f r e q u e n t l y , though, t h e r e i s a wish, maybe
subconscious, t o keep what t h e modeler did t o
h i m s e l f . A f t e r a l l , knowledge i s power.
Its
results
should
be
understandable-surprising,
perhaps,
but
not
incomprehensible.
F o r r e s t e r (1971), i n a
widely
quoted
article,
discussed
the
c o u n t e r i n t u i t i v e n a t u r e of s o c i a l systems,
and p r e s c r i b e d
computer modeling a s an
a n t i d o t e . But F o r r e s t e r was a b l e t o e x p l a i n
quite
clearly
how
he
obtained
his
counterintuitive results
(others disagree
with h i s a n a l y s i s , but t h a t is i r r e l e v a n t
here).
He would have had no credence
whatever i f h e had not been a b l e t o provide
such e x p l a n a t i o n .
3. The l i m i t s and probable range of e r r o r s
should be w e l l explained.
Few computer
models y i e l d d e t e r m i n i s t i c r e s u l t s , and a l l
a r e l i m i t e d i n t h e i r a c c e p t a b l e degree of
extrapolation.
T h i s i s o f t e n not well
understood
by
those
not
analytically
i n c l i n e d ; i t needs t o be made c l e a r .
4. The model should be f l e x i b l e enough t o deal
with
problems
t h a t had not been f u l l y
a n t i c i p a t e d , but a g e n e r a l all-purpose model
i s not a d e s i r a b l e g o a l .
S e n a t o r S. I.
Hayakawa's dictum,
"The map is not t h e
t e r r i t o r y ," although made i n q u i t e a n o t h e r
context i n h i s r o l e a s a semanticist, is
wholly a p p l i c a b l e t o modeling. A model i s a
map t h a t t e l l s us how t o g e t from one p l a c e
t o a n o t h e r , even t o some p l a c e s we had not
It cannot
o r i g i n a l l y intended t o v i s i t .
reproduce every f e a t u r e of t h e system and
s t i l l r e t a i n its u s e f u l n e s s a s a guide.
5. The
r e s u l t s should be d i s p l a y e d i n an
e f f e c t i v e and u n d e r s t a n d a b l e manner.
TOO
o f t e n model r e s u l t s a r e presented a s a r c a n e
and incomprehensible p r i n t o u t .
Territorial
defensiveness again?
R e s u l t s need t o be
p r e s e n t e d i n a form comprehensible t o t h o s e
who r e a c t t o g r a p h s r a t h e r t h a n t o columns of
figures,
to
pictures
rather
than
to
equations.
Visual p r e s e n t a t i o n almost never
r e c e i v e s enough a t t e n t i o n .
6. The model should be portable--usable on o t h e r
I
computers with a minimum of reprogramming.
have t h e f e e l i n g t h a t i n c o m p a t i b i l i t y h a s
become worse i n r e c e n t y e a r s .
This w i l l
presumably c o r r e c t i t s e l f e v e n t u a l l y , but f o r
now i t i s a s e r i o u s problem.
CONCLUSIONS
The impact of a i r p o l l u t i o n on f o r e s t s ,
e s p e c i a l l y when combined with o t h e r s t r e s s e s , h a s
biological,
s o c i a l , and p o l i t i c a l i m p l i c a t i o n s
which o p e r a t e a t s e v e r a l time s c a l e s extended over
space. The unaided human mind i s not well adapted
t o e x p l o r e t h e consequences of each of t h e l a r g e
number of
p o s s i b l e combinations of v a r i a b l e s .
T h e r e f o r e , some s o r t of computer model i s v i r t u a l l y
essential
if
t h e most
reasonable
array
of
a l t e r n a t i v e s i s t o be presented f o r r a t i o n a l
choice.
A polIcy-oriented
model is not a d e c i s i o n
maker.
It is an a i d t o informed decisionmaking.
I f i t is t o function e f f e c t i v e l y i n t h a t r o l e ,
t h e r e needs t o be mutually s u p p o r t i v e i n t e r a c t i o n s
among modelers, b i o l o g i c a l and s o c i a l s c i e n t i s t s ,
and d e c i s i o n makers.
A modeler d e a l i n g with e c o l o g i c a l p u b l i c
policy questions related t o a i r p o l l u t i o n i n
f o r e s t s needs t h e knowledge of a b i o l o g i s t , t o
understand t h e essence of t h e mechanisms by which
a i r pollution a f f e c t s biological processes.
He
needs t h e s k i l l s of a n a p p l i e d mathematician, t o
understand t h e s t r u c t u r e of t h e model and i t s
i m p l i c a t i o n s , and u s u a l l y t o d i r e c t t h e programmers
preparing
the
actual
computer
code.
Most
important, h e needs t h e p a t i e n c e and i n t e r p e r s o n a l
a b i l i t i e s of a diplomat, t o persuade t h e b i o l o g i s t
and t h e d e i c i s o n maker a l i k e t h a t h e is h e l p i n g
them t o do t h e i r job b e t t e r , and not usurping t h e i r
legitimate roles.
B i o l o g i c a l and s o c i a l s c i e n t i s t s d e a l i n g w i t h
modelers need t o r e c o g n i z e t h a t modelers a r e t h e r e
A good model,
t o h e l p them, not v i c e v e r s a .
will
usually
provide t h e
properly presented,
d e c i s i o n maker with a f u l l e r e x p l a n a t i o n of t h e
consequences of a l t e r n a t i v e pol i c i e s t h a n w i l l
unaided s c i e n t i f i c s t a t e m e n t s o r p o s i t i o n papers.
Thus, t h e s c i e n t i s t may be b e t t e r a b l e t o g e t h i s
points
across
through
the
medium
of
a
we1 1-constructed and we1 1-presented model
.
Decision makers should r e a l i z e t h a t a good
model is p r i m a r i l y a means f o r e x p l o r i n g t h e
consequences of a l t e r n a t i v e p o l i c y c h o i c e s of
n e a r l y equal rank.
I f t h e model shows one o r two
c h o i c e s t o be s o s u p e r i o r t o o t h e r s t h a t o n l y t h e y
should be c o n s i d e r e d , t h i s w i l l s u r e l y be obvious
t o competent a n a l y s t s i n t h e absence of a model.
The r e a l u t i l i t y of a p o l i c y - o r i e n t e d model i s t o
e x p l o r e t h o s e s i t u a t i o n s where t h e r e are a l a r g e
number of a1 t e r n a t i v e s which a r e " n e i t h e r a1 1 good
n o r a l l bad. The broader t h e a r r a y of c h o i c e s s e t
up f o r e x p l o r a t i o n , t h e g r e a t e r t h e f i n a l r a n g e of
o p p o r t u n i t i e s w i l l be.
F i n a l l y , I s u g g e s t t h a t t h e g r e a t e s t v a l u e of
a modeling approach t o e c o l o g i c a l problem s o l v i n g
may be i t s s t i m u l u s t o exchange of i n f o r m a t i o n
I
among d i s c i p l i n e s and among p r a c t i t i o n e r s .
mentioned, e a r l i e r , t h e r e l a t i v e l y u n s a t i s f a c t o r y
i n c o r p o r a t i o n of s p a t i a l dynamics i n f o r e s t models.
U n t i l a few y e a r s ago, t h i s would have been t r u e of
environmental biology g e n e r a l 1 y.
There have been
r e c e n t s i g n i f i c a n t advances, though, i n d e a l i n g
with s p a t i a l h e t e r o g e n e i t y i n i n s e c t d i s p e r s a l and
i n dynamics of marine plankton.
I n taxonomically
o r i e n t e d s c i e n c e , such advances t a k e a long time t o
come t o t h e a t t e n t i o n of workers i n a d j a c e n t
f i e l d s . The f a c t t h a t modeling approaches tend t o
c r o s s taxonomic boundaries seems l i k e l y t o c u t t h i s
unnecessary time l a g . T h i s a l o n e would be adequate
j u s t i f i c a t i o n f o r wider u s e of modeling i n a
complex i n t e r d i s c i p l i n a r y f i e l d such a s t h e e f f e c t
of a i r p o l l u t a n t s i n f o r e s t s .
LITERATURE CITED
Cohon, J. L., and D. H. Marks
1975. A review and e v a l u a t i o n of m u l t i o b j e c t i v e
programming t e c h n i q u e s .
Water Resour. Res.
11:208-220.
Cooper, C h a r l e s F.
1976.
Ecosystem models
and
policy. Simulation 26:133-138.
environmental
F o r r e s t e r , J . W.
1971.
Counterintuitive
behavior of
systems. Tech. Review 73(3):53-68.
social
H o l l i n g , C. S.
1973.
R e s i l i e n c e and s t a b i l i t y of e c o l o g i c a l
systems. Ann. Rev. Ecol. Systematics 4: 1-23.
H o l l i n g , C. S. [Ed.]
1978.
Adaptive environmental assessment and
management. Wiley Inter-Science, Chichester ,
U.K.
377 pp.
Kates, Robert W.
1978.
Risk
assessment
of
environmental
hazard (SCOPE 8 ) .
John Wiley and Sons,
New York, 112 pp.
b u c k s , Orie
1980. Acid r a i n : l i v i n g r e s o u r c e i m p l i c a t i o n s
and management needs.
Trans. 45th North
[In press]
Amer. W i l d l i f e Nat. Res. Conf.
Meadows, Dennis
1975.
A c r i t i q u e of short-term
perspectives
i m p l i c i t i n most r e s o u r c e models.
I n Mineral
Materials
Modeling:
A
state-of-the-art
W.
A.
Vogely,
ed.,
pp. 66-80.
Review.
Shugart, H. H., Jr., T. R. Crow, and J. M. Hett
1973.
F o r e s t s u c c e s s i o n models:
a rationale
and
methodology
for
modeling
forest
s u c c e s s i o n over l a r g e regions.
F o r e s t Sci
19 :203-2 12.
.
S t a r r , Chauncey, and C h r i s Whipple
1980.
Risks
of
r i s k decisions.
206: 1114-1119.
Science
C., H. B. McLaughlin, and H. H. Shugart
1980. Simulated f o r e s t response t o c h r o n i c a i r
p o l l u t i o n s t r e s s . J. Env. Q u a l i t y 9:43-49.
West, D.
Historical Perspectives and
International Concerns About Air
Pollution Effects on Forests1
Edwin Donaubauer2
Abstract: Air pollution from man's activities has a long history; real hazards for forest veg- etation occurred more than a century ago which marked the starting point of forest research in the field. The objectives of research have been subject to a steady metamorphosis from sim- ple causal relationships to the task of invest- igating the long-term influence of pollutant mixtures on trees directly and on entire eco- systems. The IUFRO Subject Group S2.09, Air Pollution, encourages interdisciplinary work in the field and offers an organizational home for close cooperation on an international basis. The consideration of air pollution effects on forest ecosystems goes far beyond limited for- est interests, the findings can provide fund- amental data on the deterioration of the hu- man environment. Some forest insect pests develop outbreaks
characterized by high insect population densities that use up the food resource represented
by the host species. The direct damage by insects and the predisposition of weakened trees
to certain diseases both result in a serious
degradation or even destruction of the local
forest environment.
To some extent man-made air pollution problems show some similar aspects. In many regions of the world mankind cleared the forests
for agriculture, for settlements, for roads,
for mining, for outdoor recreation, etc. Wood
1
Presented at the Symposium on Effects of Air
Pollutants on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, California, U.S.A.
'~ead, Institute of Forest Protection,
Federal Forest Research Institute,
Vienna, Austria
Deputy Coordinator, IUFRO, Division 2
is still in high demand as an energy source, and in fact is still the most important source for over 90 percent of the world's population. Col-
lection of fuel wood and the harvesting of timber for many uses have influenced the ex- tension and quality of forests over long per- iods of prehistoric and historic time. All these activities had, at least in some major regions of the globe, serious consequences for the ecosystem and human environment. We are reminded of the historical fact, that 2000 years ago forests existed around the Mediterranean Sea and protected large and prospering ag- ricultural areas in North Africa, where de- serts are now present. These were direct in- fluences, but among others an additional in- direct threat developed by the quick progress in technology and by increasing quantities and numbers of toxic substances released into the air. Certainly, man-made air pollution has been mentioned long ago in historic times, but the dimensions of the problem have changed in re- lation to regional economic and technical de- velopments. The effects of air pollution to forest ecosystems were and seem still to be
underestimated, maybe for these reasons: -
-
symptoms a r e o f t e n u n s p e c i f i c , o r develop
l a t e and slowly, o r a r e even i n v i s i b l e
( a s depression of growth increment) ;
s e r i o u s changes i n f o r e s t ecosystems may become obvious only a f t e r many years of accumulation of low concentrations o r amounts
of t o x i c substances (heavy metals, a l kaline dusts, acid rain).
t r e e s a r e more s e n s i t i v e t o widely d i s t r i b uted p o l l u t i o n than humans and t h i s d i f ference i s not f u l l y known o r r e a l i z e d .
REMARKS ON HISTORY
Perhaps Pliny (65 A.D.) was t h e f i r s t t o
observe and d e s c r i b e apparent Sop-damage t o
vegetation surrounding a smelter. Later on
we find r e f e r e n c e s f r e q u e n t l y i n documents of
t h e Middle Ages concerning a i r p o l l u t i o n by
c o a l burning; i n general people of higher so-,
c i a 1 c l a s s e s f e l t inconvenienced. Especially
i n such r e p o r t s from England and Central
Europe persecutions happened even a t t h a t time
i f a i r p o l l u t i o n was caused i n a prohibited
a r e a o r time.
A i r p o l l u t i o n became more than a l o c a l and
occasional a f f a i r when i n d u s t r i a l i z a t i o n and
the use of f o s s i l energy resources increased
r a p i d l y i n Western and Central Europe during
t h e past century. By t h e time f o r e s t research
i n s t i t u t e s and f o r e s t f a c u l t i e s were estabmore than a hundred years ago
they
lished
had s e v e r a l r e p o r t s o f p r i o r experience and
observations of b o t a n i s t s t o draw upon. Theref o r e f o r e s t research was stimulated t o pay a t t e n t i o n t o a i r p o l l u t i o n problems from t h e beginning. The present r e s e a r c h p r o j e c t s provide
numerous p u b l i c a t i o n s on a i r p o l l u t i o n e f f e c t s .
-
-
CHANGING AIMS AND TASKS
The o b j e c t i v e s of r e s e a r c h p r o j e c t s conc e n t r a t e d f i r s t on sulphur dioxide including
methods f o r d e t e c t i o n and e v a l u a t i o n of a i r
p o l l u t i o n damage. Among t h e s e e a r l y works we
find very forward-looking ones, a s Rusnov' s
(1919) study about t h e i n f l u e n c e of ' a c i d
r a i n ' ( t h i s term was introduced much l a t e r )
on f o r e s t s o i l s . Several a u t h o r s proved t h e
use of chemical a n a l y s i s of f o l i a g e f o r det e c t i o n and e v a l u a t i o n of a i r p o l l u t i o n (SO2,
HF) and i t s e f f e c t s on f o r e s t stands. These
p u b l i c a t i o n s caused long l a s t i n g d i s c u s s i o n s
and s t i m u l a t e d f u r t h e r i n v e s t i g a t i o n s ; however, many years passed u n t i l t h e chemical
a n a l y s i s of f o l i a g e (needles) became a u s e f u l
t o o l f o r a g r e a t number of cases. Step by
s t e p t h e method was r e f i n e d , so t h a t today
s u f f i c i e n t knowledge i s a v a i l a b l e f o r proper
sampling, and t h e t h r e s h o l d s of n a t u r a l s u l f u r
and f l u o r i n e c o n t e n t s and t h e i r v a r i a t i o n a r e
b e t t e r defined.
C e r t a i n l y , s u l f u r dioxide i s s t i l l t h e poll u t a n t occurring over l a r g e s t a r e a s , but t h e
l i s t of substances t h u s f a r i d e n t i f i e d a s r e sponsible f o r damage t o f o r e s t t r e e s becomes
longer and longer. More a t t e n t i o n i s now given
t o i n d i r e c t and chronic e f f e c t s of a c i d i c o r
a l k a l i n e p r e c i p i t a t i o n and heavy metals on
f o r e s t ecosystems.
Formerly, t h e i n t e r e s t o f f o r e s t r e s e a r c h
concentrated on a s i n g l e - p o l l u t a n t - s i n g l e - t r e e
species r e l a t i o n s h i p .
Today, increased e f f o r t s
a r e invested i n e l u c i d a t i n g t h e complex i n fluences on f o r e s t ecosystems and studying
t h e i n t e r a c t i o n of p o l l u t a n t mixtures which
occur i n many cases.
Regional i n v e s t i g a t i o n s on a i r p o l l u t e d
f o r e s t zones use a l l a s s i s t a n c e of modern
technology, such a s remote sensing combined
with physiological, chemical and t r e e mens u r a t i o n methods f o r v e r i f i c a t i o n .
Forest a i r p o l l u t i o n problems a r e linked
with t h e economic standard i n general and with
c e r t a i n i n d u s t r i a l development.
But i t i s n o t n e c e s s a r i l y so, t h a t only
point sources of a i r p o l l u t i o n o r concentrat i o n s of i n d u s t r i e s cause s e r i o u s problems.
Automobile t r a f f i c o r even a s i n g l e source
a r e a can under s p e c i f i c o r o g r a f i c and meteoro l o g i c c o n d i t i o n s lead t o p o l l u t a n t accumul a t i o n and perhaps t o heavy damage. F u r t h e r ,
we a r e l e a r n i n g more about long d i s t a n c e poll u t a n t t r a n s p o r t over hundreds and thousands
of kilometers.
The experience i n n a t i o n s with highly developed i n d u s t r y makes i t a d v i s a b l e t o s t i m u l a t e more i n t e r e s t i n t h i s f i e l d of r e s e a r c h
i n many developing c o u n t r i e s i n t h e world.
F i r s t of a l l t h e experiences of o t h e r s should
be transmitted and applied i n a l l planning
f o r economic development t o avoid t h e same
h i s t o r i c a l lessons received by many developing
c o u n t r i e s . There a r e many f o r e s t r e s e a r c h
workers and i n s t i t u t i o n s i n North America,
Europe (including t h e A s i a t i c p a r t of USSR),
and Japan who a r e experienced with t h e v a r i o u s
a s p e c t s of a i r p o l l u t i o n e f f e c t s on f o r e s t
ecosystems and could provide s c i e n t i f i c i n formation and a s s i s t a n c e .
I U F R 0 AND AIR POLLUTION RESEARCH
The I n t e r n a t i o n a l Union of F o r e s t Research
Organizations (IUFRO) has s i x major organiz a t i o n a l d i v i s i o n s . Division 2 , 'Forest
P l a n t s and Forest P r o t e c t i o n ' i s home f o r t e n
Subject Groups, one of which i s S2.09 - ' A i r
Pollution.'
The t i t l e s of t h e various Working
P a r t i e s e l u c i d a t e . t h e i n t e r d i s c i p l i n a r y scope:
Researchers a r e included from t h e f i e l d s of
f o r e s t mensuration, s o i l s c i e n c e , pathology,
remote sensing, t r e e physiology, e t c . They work
t o g e t h e r , and exchange research r e s u l t s t h a t
s t i m u l a t e t h e i r f u r t h e r research. This IUFRO
Subject Group has a long h i s t o r y of a c t i v i t y .
For more than a q u a r t e r of a century meetings
have brought t o g e t h e r an i n c r e a s i n g number of
p a r t i c i p a n t s . A few western and c e n t r a l European
c o u n t r i e s were represented a t f i r s t ; now more
c o u n t r i e s from e a s t e r n and southern Europe a r e
represented too, a s w e l l a s a slowly i n c r e a s i n g
number of p a r t i c i p a n t s from Canada and t h e U.S.A.
The eleventh meeting of a l l Working P a r t i e s w i l l
be held this year in Graz, Austria and previous conferences were hosted by nine other European countries. It is somewhat disappointing that the group met only once in another continent: Gainesville, Florida, U.S.A. at the occasion of the IUFRO Congress in 1971. We expect to have a meeting at the occasion of the 1981 IUFRO Congress in Japan. The interdisciplinary scope of all Subject Group meetings makes them attractive to a cer- tain group, seldom represented at such scien- tific conferences. We could characterize this group as 'consumers' of research results in- cluding: forest managers, representatives from industries, and sometimes politicians. There are of course some difficulties in accommodating the needs of each group, but I consider the interest in such meetings as an expression for a demand to receive the information from the scientists directly and not via more tradition- al channels, i.e., technical publications. I feel we should think of possibilities for such direct information flow in specific fields like air pollution where we find more and more vital interest from the public. I feel that this international symposium sets the stage for new conceptualizations by placing the view of effects of air pollutants on forest ecosystems into the center of the de- liberation. The discussions here should stim- ulate further research and interdisciplinary, international cooperation. In addition I will emphasize that air pol- lution effects on forests are not only a question for researchers or foresters, but of fundamental interest to mankind. That may seem overstated but forest ecosystems demon- strate due to the long rotation periods the dynamics and the consequences of long-term influences on complex ecosystem-level processes. Various pollutant effects that are dangerous not only to the forests themselves, as an im- portant resource, but also as an invaluable part of the human environment can be predicted by ecosystem-level research. In this sense one can consider the forest ecosystems as sensitive warning systems for the vital, fundamental interests of life.