Perspectives for Developing the Land Component of the Biosphere Program

NOT FOR QUOTATION WITHOUT THE PERMISSION OF THE AUTHOR

PERSPECTJSTS FOR DEVELOPING THE LAND COMPONENT OF THE BIOSPHERE PROGRAM

Zsolt Harnos

July 1986 CP-86-22

PUBLICATION NUMBER 27 of t h e project:

E c o l o g i c a l l y S u s t a i n a b l e Development of t h e B i o s p h e r e

C o l l a b o r a t i v e P a p e r s r e p o r t work which h a s not been performed solely at t h e International Institute f o r Applied Systems Analysis and which h a s received only limited review. Views or opinions e x p r e s s e d h e r e i n do not necessarily r e p r e s e n t those of t h e Institute, i t s National Member Organizations, or o t h e r organizations supporting t h e work.

INTERNATIONAL INSTITUTE FOR APPLIED SYSTEMS ANALYSIS 2361 Laxenburg, Austria

Preface

One of t h e goals of IIASA's Biosphere P r o j e c t i s t o develop s t r a t e g i c frame- works showing t h e n e t impact of human activities on p r o p e r t i e s of t h e environment t h a t are r e l e v a n t f o r sustainable human development. The first contribution t o t h i s goal w a s Paul Crutzen and Thomas Graedel's p a p e r on "The r o l e of atmospheric chemistry in environment

-

development interactions", published in W.C. Clark and R.E. Munn (eds.) 1986. S u s t a i n a b l e Development of t h e B i o s p h e r e (Cambridge:

Cambridge University P r e s s ) .

In t h i s p a p e r Zsolt Harnos begins t h e task of shaping a complementary frame- work f o r t h e land/soil system. The challenge i s in many ways g r e a t e r t h a n t h a t f o r t h e atmosphere, due t o t h e extreme spatial heterogenity of soil systems. Dr. Har- nos' p a p e r i s especially useful as a n e f f o r t t o bridge t h e gap t h a t normally s e p a r a t e s t h e microscale of studies of soil dynamics from t h e macroscale s u r v e y s of soil

state

and classification.

-

iii

-

A c k n o w l e d g e m e n t s

This p a p e r reflects t h e e f f o r t s of many people. I

a m

g r a t e f u l t o William C.

Clark, l e a d e r of IIASA's Biosphere p r o j e c t , who provided a stimulating environment f o r my writing in t h e summer of 1985. I am indebted t o Janos Hrabovsky, Kalman Rajkai, F e r e n c Toth, and t h e p a r t i c i p a n t s in IIASA's 1985 Young Scientists' Summer Program f o r t h e i r comments a n d suggestions. Special t h a n k s t o John Ormiston f o r editing t h e p a p e r .

A b o u t the A u t h o r

Dr. Zsolt Harnos i s Deputy D i r e c t o r of Computer C e n t e r of t h e National Plan- ning Office, Budapest, Hungary. He h a s been working on modeling of a g r i c u l t u r a l systems o v e r t e n y e a r s , and h a s s e v e r a l publications in this field. He

was

t h e lead- ing modeler of two major studies o n t h e f u t u r e of t h e Hungarian a g r i c u l t u r e organ- ized by t h e Hungarian Academy of Sciences. He a l s o contributed t o t h e Food and Agriculture Program

at

IIASA.

His mailing a d d r e s s is:

Computer C e n t e r of t h e National Planning Office Angol u. 27.

Budapest

H-1149 Hungary

CONTENTS

1 . INTRODUCTION

2 . DEFINITION AND CLASSIFICATION OF LAND 3. LAND EVALUATION

4 . WHAT DETERMINES THE PRODUCTION OF REGIONS?

4 . 1 . A r e a a n d l a n d u s e

4 . 2 . P r o d u c t i v i t y o f a r e g i o n

5. FUNCTIONING OF THE LAND-USE MODEL OF THE BIOSPHERE PROGRAM

-

v i i

-

PERSPECTIVES FOR DEVELOPING THE LAND COMPONENT OF THE BIOSPHERE P R O G M

Zsolt Harnos

Computer Center of t h e National Planning Office Budapest, Hungary

1. Introduction

The basic goal of IIASA's Biosphere Program is t o describe t h e long-term in- teractions of human activity and biosphere elements and t o call attention t o t h e damaging effects of those interactions and t h e i r probable consequences. I t s aim i s t o describe such processes f o r l a r g e regions, by synthetizing t h e knowledge accu- mulated t o date.

Describing probable f u t u r e alternatives may r e s u l t in changes in t h e attitudes of politicians and decision makers, and s o bring attention t o t h e need t o consider economical-ecological a s p e c t s versus t h e short-term economic t r e n d s currently enforced in most

cases.

I a m convinced t h a t a change in attitude is a n essential precondition f o r t h e sustainable utilization of resources.

The Biosphere Program deals with t h e problems of t h e biosphere in

t e r m s

of f o u r main components:

-

atmosphere,

-

^land,

- ^water,

^and

-

^biota.

In t h e initial phases w e handle t h e f a c t o r s t h a t a f f e c t t h e elements of t h e bio- s p h e r e separately, but l a t e r in t h e synthesizing phase they will b e combined and t h e processes will b e analyzed in a complex, i n t e r r e l a t e d way, as shown in Figure 1.

The scenarios describe t h e possible "development paths" (e.g., population growth, energy policy, consumption, technical development,

water

use, etc.). The output of t h e system answers questions such as:

How do t h e elements of t h e biosphere change due t o t h e above development paths?

How does t h e carrying capacity of t h e E a r t h and life conditions in general change?

Which processes lead t o harmful consequences in t h e different scenarios?

This list of possible questions is far from complete, but i t is useful t o provide a n outline t o b e t t e r understand t h e concept.

S c e n a r i o s

~ t m o s ~ h e r s Water

\

^Biota

^IL

^{/ A}

Figure 1.

In t h e

rest

of t h i s p a p e r only t h e land component of t h e b i o s p h e r e i s con- sidered. W e focus o n t h e r o l e of land with r e s p e c t

to

human conditions, specifically in food production. In t h i s c o n t e x t t h e following questions c a n b e raised:

What i s t h e c a r r y i n g capacity of t h e E a r t h ?

What are t h e f a c t o r s t h a t change t h i s c a r r y i n g c a p a c i t y ?

How c a n w e provide, in t h e long-term, a n i n c r e a s e in t h e E a r t h ' s c a r r y i n g capacity t h a t p a r a l l e l s t h e population i n c r e a s e ?

In t h e above questions, by E a r t h w e mean t h e land t h a t i s potentially a r a b l e . These questions

are

all concerned with c a r r y i n g c a p a c i t y , b u t t h e r e i s no generally

ac-

c e p t e d definition of this. To b r i d g e t h i s problem,

a

consistent conceptual frame- work h a s t o b e established in a c c o r d a n c e with t h e goals of t h e Biosphere Program.

The conceptual framework d e s c r i b e s t h e h i e r a r c h i c a l , areal partitioning of land and, linked

to

this, t h e evaluation system (productivity) of t h e building elements of t h e area. The conceptual system, i t s elements and t h e r e l a t i o n s of t h e elements

are

shown in Figure 2.

The details

are

explained later.

2. Definition and classification of land

With t h e aim of t h e Biosphere P r o g r a m in mind, a p r a c t i c a l definition of land is: "that t e r r e s t r i a l p a r t of t h e E a r t h ' s s u r f a c e on which a significant quantity of biomass i s formed". This

area

c a n b e b r o k e n down into t h r e e major groups:

-

a r a b l e land 1.5 x 10' h a

-

meadows and p a s t u r e s 2.6 x 10' h a

-

productive f o r e s t 4.1 x 10' ha.

The

rest

of t h e continents (some 6.2 x 10' ha) i s unsuitable f o r plant production.

With r e s p e c t t o t h e E a r t h ' s c a r r y i n g c a p a c i t y t h e

m o s t

important f a c t o r i s t h e area of a r a b l e land and i t s productivity. According t o FA0 estimates, potentially

Carrying capacity (World)

P e r capita

requirement economic conditions,

distribution Production of

region (g)

Land use of Productivity of

region (me) a mosaic (g/m 2,

I I ^I I I

Climate Genetic Soil fertility Cultivation Other

d e v e l o ~ m e n t 1 practice factors

1 I I I

Physical Chemical Biological Soil

characteristics charecteristics charecteristics phase

+-I

+l-n A 1

Aggregation Global

Regional

Mosaic

Local properties

Figure 2.

a r a b l e land could be

as

high

as

3.2 x 10' ha.

The distribution of a r a b l e and potentially a r a b l e lands is uneven among t h e continents. In Europe, 31% of t h e total area is under cultivation, while in Africa only 9% is. Thus, t h e r e is practically no r e s e r v e in Europe while t h e r e is much in Africa [5]. This definition and grouping provides a very rough categorization of land, since i t combines nonhomogeneous regions. Land i s nonhomogeneous in space and its productive features (chemical and physical properties of t h e soil, organic

matter

content, etc.) are highly dependent on o t h e r external conditions, such a s hydrology, climate, etc.

Therefore, t h e description of global processes can only be built up gradually.

That is:

The Earth's surface has t o be divided into ecologically homogeneous

re-

gions (mosaics).

These mosaics must be classified into higher groups, eg. into regions, which can be continent-like.

These regions can b e combined t o form t h e complete Earth's surface.

Each of these hierarchical levels is discussed f u r t h e r below.

(1) With r e s p e c t t o t h e global c h a r a c t e r of t h e Biosphere Program t h e mosaics would be homogeneous in t h e sense t h a t they show a similar behavior with r e s p e c t t o t h e most important processes described in t h e Biosphere Program.

Such ecologically homogeneous regions can be:

-

potentially salt-af f ected regions,

-

potentially acid soils,

-

potentially erodable soils,

-

potentially irrigable land, etc.

The processes t h a t occur on these mosaics are relatively w e l l known and "hy- pothetical models" can be constructed t o describe t h e most important rela- tionships. These models can be

-

simple mathematical models,

or

-

input-output models t h a t integrate e x p e r t judgements.

The input list related t o land i s included in t h e scenarios and in t h e actual characteristics of t h e o t h e r elements of t h e biosphere (atmosphere, water, and biota).

(2) Processes t h a t occur in t h e regions can be described using a model system of mosaics, taking into consideration t h e exogenous variables of t h e system, such

as

population growth, urbanization, energy consumption, afforestation, climate, etc. The parameter list can be completed only a f t e r determining t h e main relations of t h e "biosphere system". The model system can be validated using t h e available data base over a certain time period.

(3) From regional models one can easily construct t h e so-called "world-model", which describes t h e E a r t h ' s carrying capacity. The study of carrying capaci- ty i s not an easy task e i t h e r , because t h e distribution of products is not equal and thus a local surplus in one place is not available for those in o t h e r places who need them. To solve these problems requires t h e consideration of dif- f e r e n t social and economic processes.

3. Land evaluation

The regional a s p e c t includes t h e following problems: How t o c h a r a c t e r i z e t h e s e p a r a t e p a r t s and what kind of evaluation system t o use f o r comparing them and describing any changes? A possible solution could be t h e evaluation system described h e r e a f t e r , which is related t o t h e h i e r a r c h i c a l modeling of t h e land as well.

A given piece of land, a so-called mosaic, can be characterized by i t s p r o d u o t i v i t y , which in

t e r m s

of land use, i s determined by f o u r group of factors:

-

genetic development,

-

climate change,

-

change in soil fertility,

-

cultivation p r a c t i c e ,

-

o t h e r f a c t o r s .

External effects can also be considered, such as pollution (eg. acid rain) and

water

management, by which w e mean water use t h a t directly affects productivity:

f o r example, building artificial lakes and water basins, which can r a i s e t h e ground- water table and cause salinization. We d o not deal with t h e s e h e r e .

A s

w a s

mentioned e a r l i e r , t h e E a r t h ' s s u r f a c e is r e p r e s e n t e d

as

regions, re- gions built of ecologically homogeneous mosaics. Mosaics are unambiguously determined by t h e i r defining environmental parameters, such

as

geographical lo- cation, relief, soil type, climate,

etc.

Thereby, mosaics a r e located geographically and

are

considered t o be homogeneous

-

in productivity,

-

in t h e i r reaction t o e x t e r n a l effects t h a t influence t h e i r soil and ecological p r o p e r t i e s (salinization, erosion, etc.).

Productivity needs t o b e defined f o r these homogeneous mosaics. There is no known, e x a c t causal relationship between t h e productivity of a piece of land and its determining environmental parameters. Let us sidestep t h e problem and define productivity

as

a dynamic p r o c e s s and assume i t s general development.

Furthermore, assume t h a t t h e environmental conditions (climate, soil fertility) are stable during t h e study period. S o t h e gradual increase in productivity i s solely due t o biological (genetical) improvement and improvement in cultivation practices.

The base p r o d u c t i v i t y of f o r e s t s is determined by t h e continuous exploitation of "wood yield". The base productivity is ultimately stable f o r natural f o r e s t s , while f o r plantation f o r e s t r y i t is assumed t o be a monotonously increasing func- tion of time. The actual n a t u r e of t h e function will be determined by o t h e r assump- tions; i t i s too soon t o consider them h e r e .

In t h e c a s e of meadow-pastures t h e base productivity can be expressed p r a c - tically in

terms

of hay yield o r grazing capacity. The definitions cannot substitute f o r each o t h e r , but, depending on t h e land considered, i t will b e p r a c t i c a l t o use sometimes one, sometimes t h e o t h e r . Increases in t h e productivity of meadow- p a s t u r e s come from genetic and agrotechnological development, while in livestock carrying capacity improvements in fodder utilization are important.

When characterizing a r a b l e lands problems o c c u r because of changing land use and t h e constraints due t o specific conditions required f o r c r o p production. To substitute "production" by "carrying capacity"

seems to

eliminate this problem.

With time, in e v e r y l a r g e r region a p a r t i c u l a r s t r u c t u r e of consumption h a s been formed according t o t h e local environmental conditions. This s t r u c t u r e i s mainly

t h e r e s u l t of plant-growing possibilities in

a

given region. This consumer s t r u c - t u r e c a n b e used

as

a r e f e r e n c e point, in which c a s e productivity means t h e number of people t h a t c a n be supplied by a given s t r u c t u r e . In t h i s c a s e , changes in consumer behavior may c a u s e problems.

Productivity c a n a l s o b e c h a r a c t e r i z e d by t h e a v e r a g e yield of a c e r t a i n r e f e r e n c e c r o p . In t h i s c a s e , i t i s p r a c t i c a l t o choose t h e most important c r o p of t h e region (wheat, c o r n , r i c e , barley,,etc.)

as

a r e f e r e n c e c r o p and t o deduce from i t s changes t h e c a r r y i n g c a p a c i t y of t h e land. I t i s n e c e s s a r y t o emphasize t h a t t h e productivity function is not only determined by t h e mosaic but a l s o by t h e time period considered, during which i n c r e a s e s o c c u r due t o a g r o t e c h n i c s , genetics,

etc.

The s l o p e of t h e productivity function c a n b e determined by a time-series analysis. The d e r i v e d productivity function c u r v e may b e modified by changes in t h e

state

v a r i a b l e s of t h e land and by applied a g r o t e c h n i c s ,

so

t h e a c t u a l produc- tivity remains within a c e r t a i n r a n g e around t h e determined productivity function (see Figure 3).

t 0 t

( p r e s e n t s t a t e )

Figure 3.

W e assume t h a t t h e environmental f a c t o r s (soil f e r t i l i t y and climate)

are

con- s t a n t in t h e study period f o r t h e function t h a t d e s c r i b e s t h e b a s e productivity. The upward s h a p e of t h e function i s caused by g e n e r a l genetic development and im- proving cultivation p r a c t i c e s . Maximum productivity c a n b e r e a c h e d by maximum utilization of t h e land, by application of t h e b e s t available cultivation p r a c t i c e s , and, if n e c e s s a r y , by amelioration or r e s t o r a t i o n . Minimum productivity i s d e t e r - mined by low level cultivation p r a c t i c e s and land degradation.

In a given p e r i o d , t h e potential productivity is e x p r e s s e d by t h e interval:

[ I & ( k , t ) , I,,,(kSt)l

Thus, t h e a c t u a l productivity falls somewhere within t h e interval. In t h e b a s e s c e n a r i o , t h e a c t u a l productivity of t h e mosaic i s determined by soil f e r t i l i t y (sf) and cultivation p r a c t i c e (cp ), formulated as:

and

I t i s n e c e s s a r y t o emphasize t h a t t h i s productivity i s valid if changes d o not o c c u r in t h e climate and in t h e e x p e c t e d genetic development. If changes are as- sumed in t h e s e , t h e c u r v e s should b e modified according t o t h e new hypothesis.

The p r o d u c t i o n of r e g i o n s c a n b e c o n s t r u c t e d from land u s e and t h e produc- tivity of mosaics. The definition i s given as follows:

Let u s suppose t h a t a given region i s built up from [& p i e c e s of mosaics, where

&

e x p r e s s e s t h e area of t h e k t h mosaic. Each mosaic h a s a s p e c i f i c productivity function, as d e s c r i b e d above, which are t h e implicit functions of cultivation p r a c - tice. With r e s p e c t t o land use, e a c h mosaic i s divided into f o u r c a t e g o r i e s

-

ar- a b l e land, meadow-pasture, f o r e s t , unused area.

These c a t e g o r i e s change in time, t h u s

&,, = &

^,, (t ), and t h e a c t u a l

distribution i s given in t h e scenarios. The a c t u a l production of t h e region in time t i s

where t h e index

n

means t h e cultivation t y p e ( a r a b l e , f o r e s t , etc.). The produc- tion c a p a c i t y (i.e., maximum production) of t h e region i s given by solving t h e fol- lowing e x t r e m e problem:

P m a x f r

I I

g o t ( t ) ^s assuming t h a t

jrgot ( t )

=

[ f i . r g o t ( t ) , f ~ . r g o t ( t ) * f ~ . r + o t ( t ) ] * K

f n .r g o t ( t )

= C

f n , - ( k * t ) & , n ( t )

k =1

The last assumption e x p r e s s e s r e s t r i c t i o n s in land u s e and P-max i s t h e P a r e t o op- timality

.

However, o n e c a n p r o d u c e a meaningless land-use s t r u c t u r e in t h i s way, s o t o d e s c r i b e land u s e using s c e n a r i o s seems p r a c t i c a l . Then, production c a p a c i t y i s defined as:

H e r e

&

^,, (t ) i s determined by t h e a c t u a l scenario.

F o r t h e E a r t h in t o t a l , production c a n b e substituted by t h e c a r r y i n g capaci- ty. The E a r t h ' s c a r r y i n g c a p a c i t y i s determined by population requirements and by t o t a l production of t h e regions. If t h e regions are considered as closed systems,

t h e c a r r y i n g c a p a c i t y c a n b e defined f o r them similarly, which would r e g u l a t e t h e population of t h e given region,

as

h a s happened historically in subsistence so- cieties. However, t h e g e n e r a l development of society h a s eliminated t h e enclosure of t h e system such t h a t , because of t h e development of t h e division of l a b o r , t r a d e , e t c . , t h e c a r r y i n g c a p a c i t y of

a

region i s difficult t o determine.

S o w e will use c a r r y i n g capacity

at

t h e global scale only. Carrying capacity a l s o changes o v e r time, just as t h e above-mentioned production and productivity.

In s p i t e of t h i s , i t s introduction s u i t s t h e goal of t h e Biosphere Program, since t h e program i s c o n c e r n e d with global questions, such a s , e.g., t h e c a r r y i n g c a p a c i t y of t h e E a r t h . This problem cannot b e solved exactly, b u t i t i s quite p r a c t i c a l t o analyze whether t h e p r o c e s s e s affect i t positively o r negatively. Such processes are. e.g., land

area

reduction, changes in land productivity, improvement in nu- t r i e n t supply,

etc.

Depending on t h e s e t r e n d s one c a n postulate t h e f u t u r e food production c a p a c i t y of t h e E a r t h o r , indirectly, t h e c a r r y i n g capacity.

Of c o u r s e , t h e e f f e c t i v e c a r r y i n g c a p a c i t y i s not only determined by t h e t o t a l food quantity produced, b u t i s a l s o influenced by distributional relationsships, which are affected by different political, social, and economic considerations. But w e d o not consider t h e s e issues herein.

From t h e above arguments o n e c a n see t h a t t h e analysis of c a r r y i n g capacity develops from problems r e l a t e d d i r e c t l y

to

land use. We feel t h a t t h e Biosphere Program should analyze t h e p r o c e s s e s occuring in t h e regions, s o we summarize t h e r e l a t e d problems below.

4. What determines the production of regions?

The production of a region in

a

given time, with significant simplification, i s determined by t h e following f a c t o r s :

(1) The

area

of t h e region and i t s division into cultivation t y p e s (land use) (2) The division of t h e region according t o productivity

4.1. Area and land use

The area of t h e region i s constant, but i t s division changes o v e r time.

Through history t h e e x t e n t of a r a b l e land h a s changed significantly. According t o FA0 estimates, soil loss may have a f f e c t e d

a

g r e a t e r area t h a n i s presently cul- tivated and, c u r r e n t l y , because of soil degradation t h e cultivated area is d e c r e a s - ing by 5-7 x

lo6

h e c t a r s p e r y e a r . According t o f o r e c a s t s t h e d e g r e e of soil de- crease will i n c r e a s e until t h e t u r n of t h e twentieth century and will r e a c h 1 0 x

lo6

h a / y e a r . [4] Besides soil degradation, a n o t h e r significant c a u s e of land loss i s ur- banization and industrialization.

The i n c r e a s e in land

area

occupied by settlements and t h e i r i n f r a s t r u c t u r e i s

a

consequence of t h e n a t u r a l development process. The fast i n c r e a s e in nonpro- ductive area is caused by human intervention t h a t neglects ecological conditions.

Table 1: Distribution of land in Europe

Area lo3 ha

Arable land 127506 127263 126575 126412

Permanent

p a s t u r e s 87602 86727 86349 85881

F o r e s t 152536 154630 155106 155276

Other land 89510 89608 90458 91072

Table 2: Arable h e c t a r e s p e r c a p i t a

Alternative 1951-55 1961-65 1971-75

1985 2000 Industrialized c o u n t r i e s

United S t a t e s

Other major e x p o r t e r s Western E u r o p e

Japan

Centrally planned c o u n t r i e s E a s t e r n E u r o p e

USSR

People's Rep. of China Less developed c o u n t r i e s

Latin America

North Africa/Middle E a s t Other African LDCs South Asia

Southeast Asia E a s t Asia World

Note: Arable area includes land under temporary crops (doublecropped a r e a s are count- e d only onoe), temporary meadows f o r mowing o r pasture, land under market and kitohen gardens (including cultivation under glass), and land temporarily fallow o r lying

S o u r c e : [2]

In principle, i t is possible t o recultivate nonproductive a r e a s , f o r example, by t h e watering of d e s e r t e d a r e a s , but t h e s e days t h i s o c c u r s only t o a small d e g r e e and y e t r e q u i r e s significant investments.

In Europe, t h e d e c r e a s e of a r a b l e land has been caused mainly by urbaniza- tion and industrialization. In Table 1 w e illustrate t h e s e processes in Europe.

The d a t a show t h a t o v e r 8 y e a r s a r a b l e land h a s d e c r e a s e d by roughly 1% and permanent p a s t u r e s by 2%, and f o r e s t has increased by 2%. In Hungary, t h e plough- land h a s d e c r e a s e d by roughly 14% o v e r 40 y e a r s . In Europe t h e r e are no

"reserves" from which this loss can b e replaced.

The r e l a t i v e d e c r e a s e of a r a b l e land c a n b e b e t t e r shown with r e s p e c t t o t h e population,

as

in Table 2.

The d a t a show t h a t t h e world a v e r a g e h a s d e c r e a s e d by 50%, thus, assuming t h e same consumption, t h e yields should b e twice

as

much

as

before. This increase c a n b e achieved by high level agricultural technology (in t h e developed countries p e r capita production

w a s

doubled o v e r a n even s h o r t e r time). A shift in t h e type of land use o r in t h e i n c r e a s e of nonproductive

areas

not only h a s

a

d i r e c t effect on food production, but also on t h e climate, hydrological conditions, and biochemi- cal cycles, all of which have unpredictable consequences.

One t h i r d of t h e E a r t h ' s t e r r i t o r y is covered by f o r e s t s . Out of t h e 4.5 x 10' h a f o r e s t a r e a , 2.7 x 10' h a

are

"closed forest", where

at least

20% of t h e

area

i s covered by canopy. This distribution is t h e r e s u l t of a long development process.

In t h e dynamic p r o c e s s of land utilization today, industrialized societies t r y t o maintain and increase f o r e s t s , while in many developing countries t h e f o r e s t a c r e a g e is decreasing. In Europe, however, a 8 t o 9% growth in f o r e s t

area

is planned. The main problem is t h a t in t h e p o o r e r , developing countries t h e h a r v e s t is g r e a t e r t h a n t h e annual growth. In Europe, t h e USSR, and t h e US, t h e annual h a r v e s t i s less t h a n t h e growth. [2]

The composition of agricultural land with r e s p e c t t o t h e quality h a s also changed unfavorably. In most c a s e s , urbanization and industrialization occupy f e r - tile t e r r i t o r i e s (riverside, plain a r e a s ) , but t h e r e

are

no e x a c t d a t a on this.

4.2. Productivity of a region

According t o t h e definitions introduced above, t h e productivity of

a

mosaic is determined by s e v e r a l f a c t o r s , which, with some simplification, c a n b e grouped as:

-

genetic development,

-

climate change,

-

change in soil fertility,

-

cultivation p r a c t i c e ,

-

o t h e r factors.

In all five cases t h e change t h a t o c c u r s i s emphasized, since in t h e definition of productivity genetic development, climate, and soil fertility

are

included.

GENETIC DEVELOPMENT

To d e s c r i b e genetic development one c a n consider s e v e r a l scenarios instead of one. I t is assumed t h a t c r o p varieties of significantly higher productivity c a n b e produced by biotechnological methods. which would cause

a

significant i n c r e a s e in productivity, but i t could a l s o b e diminished.

CLIMATE CHANGE

In t h e long-term i t i s q u i t e p r a c t i c a l t o consider climatic change. Climatic changes c a n b e caused by, among o t h e r things, t h e unbalanced ecology of l a r g e areas. Without drawing any final conclusions, t h e annual a v e r a g e precipitation values f o r Hungary

were

calculated r e g a r d i n g t h e last 1 0 0 y e a r s (see Figure 4).

Data show a significant decline in t h e a v e r a g e values.

G O O

^"

500

..

Year Changes in ten-year precipitation a v e r a g e s

(1871-1980) Figure 4.

SOIL FERTILITY

The definition of productivity i s r e l a t e d t o land mosaics, and i t i s p r a c t i c a l t o make two assumptions:

(1) Their productivity i s similar with r e s p e c t t o land use.

(2) They

react

similarly t o endogenous and exogenous actions.

The second assumption means t h a t mosaics

react

identically t o erosion, salini- zation, acidification,

etc.

Beside t h e s e constant c h a r a c t e r i s t i c s of land, produc- tivity i s a f f e c t e d by t h e physical, chemical, and biological conditions of t h e soil, which change with time a n d h a v e d i f f e r e n t impacts which modify productivity.

The t e r m "soil fertility" i s used t o c h a r a c t e r i z e land. Any change in soil f e r - tility modifies t h e function t h a t d e s c r i b e s t h e productivity of t h e land (mosaic) (Figure 3). W e assume in

terms

of t h e b a s e productivity t h a t soil f e r t i l i t y i s con- s t a n t . However, in t h e long-term, this assumption i s not valid. Considerable land area i s exposed t o erosion, salinization, etc., which a f f e c t i t s productivity. Soil

fertility is t h e measure t h a t indicates these changes, more exactly t h e changes in productivity under t h e p r e s e n t conditions compared t o t h e previous ones.

Soil fertility can be increased by applying amelioration. In spite of t h e fact t h a t t h e r e i s no known exact relationship between soil fertility and c r o p yield w e should, somehow, handle this relationship because only through this can w e show t h e consequences of nonsustainable management practices. The parameters t h a t determine soil fertility can be divided into four groups:

-

physical characteristics,

-

chemical characteristics,

-

biological characteristics, organic

matter

content,

-

d e g r e e of erosion.

Physical characteristics include soil s t r u c t u r e ,

water

capacity, and compac- tion. Among t h e causes of soil s t r u c t u r e deterioration (compaction)

are

t h e inten- sive use of heavy machines, t h e decline in organic

matter

content of t h e soil, and irrigation. Soil compaction directly affects

water

capacity of t h e soil and via this t h e nutrient supply of plants. According t o an estimate made by Hungarian experts, soil compaction results in

a

yield loss of roughly 10%

[S].

Compaction can be elim- ipated by amelioration (deep-loosening, etc.).

Chemical characteristics include soil pH, salinization, and alkalinization, of which acidification has a significant effect on soil fertility. The sensitivity of plants t o soil acidity is different and species dependent, but t h e deterministic rela- tionship between pH and fertility i s still not known. According

to

experience t h e relationship between soil pH and relative fertility f o r wheat and alfalfa i s

as

shown in Figure 5.

[S]

fertility level

1

-

as a percentage of productivity

0,5-

pH

Figure 5.

Observations show t h a t below a certain level of pH value fertility drops sharply

Dl.

Factors t h a t cause acidification a r e :

-

acidic N fertilizers,

-

acid rain.

No analytical function i s known t h a t describes t h e relationships between causal f a c t o r s and soil pH. I t is recorded and predictable t h a t soil acidification has in- creased due t o acid rainfall from heavily industrialized regions. International con-

c e r n h a s initiated actions t o stop this unfavorable process; thus, f o r example, some developed countries have undertaken t o r e d u c e t h e i r SO, emissions by 30%.

The acidification of a g r i c u l t u r a l lands can be stopped and even t h e pH level in- c r e a s e d by e.g., ameliorative lime application.

With t h e expansion of irrigation t h e proportion of lands under

water

h a s in- c r e a s e d . According t o estimates, roughly 1 2 5 000 h a of productive land is lost an- nually through waterlogging, salinization, and alkalinization. This is only 0.06% of t h e t o t a l i r r i g a t e d a r e a , but since irrigation is applied almost solely on t h e most productive lands, t h i s phenomenon is not negligible [ Z ] .

Biological c h a r a c t e r i s t i c s and organic

matter

content t o g e t h e r c h a r a c t e r i z e t h e humus content of soil, i t s biota, and, in a b r o a d e r sense, t h e f l o r a and fauna of t h e given region. The organic

matter

content of soil v a r i e s from z e r o t o a few p e r cent. This is significant with r e s p e c t t o biomass production because i t improves t h e

water

management and nutrient supply of t h e soil. According t o

estimates,

in Eu- r o p e t h e humus content of soil t h a t h a s been under cultivation f o r a long time h a s decreased by 2 5 t o 50% with r e s p e c t t o t h e original

state

[5]. This i s p a r t l y due t o t h e use of heavy machines and p a r t l y t o soil loss, but t h e degradation of soil s t r u c - t u r e a l s o contributes t o erosion. The d e c r e a s e in organic

matter

content is influ- enced by o t h e r f a c t o r s :

The effective u s e of modern agricultural technology is r e s t r a i n e d by plant residues r e t u r n e d t o t h e soil, t h e r e f o r e , t h e by-products, stalk- and root- residues are removed from t h e biological cycle (they are usually burnt).

The f a s t decay of stalk- and root-residues can b e promoted by N-fertilizer;

t h i s i n c r e a s e s t h e d i r e c t c o s t s of nutrient supply.

The use of chemical f e r t i l i z e r s i s significantly c h e a p e r than t h e use of organ- ic f e r t i l i z e r s o r composts, besides which l a r g e

scale

methods f o r chemical f e r t i l i z e r s are b e t t e r developed.

The d e c r e a s e in soil organic

matter

r e s u l t s in t h e d e c r e a s e of microelements, which adversely a f f e c t s plant growth.

In many countries, t h e possibility of multipurpose utilization of t h e biomass h a s r e c e n t l y been considered seriously and t h e g e n e r a l remark i s t h a t a g r e a t e r s h a r e of t h e biomass should b e r e t u r n e d t o t h e soil. In Hungary, t h e dry

matter

content of t h e plant produced in plant production w a s 48 x 10' tons in 1980, more than 50% of which c a n b e considered as by-products and

wastes.

According t o ex- p e r t s , more than 60% of t h i s should b e used in t h e organic

matter

supply [3].

The d e c r e a s e in soil organic

matter

content is not only due

to

a g r i c u l t u r a l technology, b u t a l s o

to

overgrazing and burning of savannas and p r a i r i e s . The de- g r e e of t h e s e and t h e i r d i r e c t e f f e c t s cannot b e measured.

Erosion t a k e s two main forms, wind and

water.

Soil loss due t o erosion leads t o a d e c r e a s e in soil productivity. The measure of productivity loss a f t e r erosion can a l s o b e estimated but t h e r e i s no a c c e p t e d , verified relationship between t h e two. The man-caused f a c t o r s responsible f o r

water

^erosion are:

-

mode of soil cultivation,

-

c o v e r a g e of soil,

-

^organic

matter

content of soil.

The most serious loss caused by erosion o c c u r s a f t e r deforestation in t r o p i c a l

re-

gions, but t h e r e

are

a l s o some significant soil losses in North America and Europe.

The lands endangered by erosion in Europe are shown in Figure 6. (see: [5]).

Soil Erosion in E u r o p e Figure 6.

Erosion a f f e c t s

water

management (significant s u r f a c e runoff), plant nutri- tion, and soil o r g a n i c

matter

content, besides t h e reduction of t h e depth of t h e soil profile. Wind e r o s i o n mainly a f f e c t s low-lying sand areas and o c c u r s b e c a u s e of p o o r vegetation c o v e r a g e of t h e soil, d u e t o i n a p p r o p r i a t e a g r o t e c h n i c s o r over- grazing. An illustrative example of t h i s is t h e S a h e l region, where t h e c a r r y i n g capacity of t h e area i s less t h a n t h e needs of t h e human and animal population is.

The r e s u l t i s desertification, which positively f e e d s back into t h e climate through decreasing precipitation, and t h u s desertification becomes more intensive. The prediction i s t h a t t h e by 2000 d e s e r t areas will b e t h r e e times t h a t

at

t h e end of t h e 1970s [5].

To raise t h e productivity of d e s e r t s i s only possible through i r r i g a t i o n . To p r o t e c t t h e lands against wind e r o s i o n i t i s n e c e s s a r y

to

keep t h e soil c o v e r e d and t o build up wind s h e l t e r s (e.g.,

tree

rows, etc.).

The c h a r a c t e r i s t i c s of soil f e r t i l i t y brought a b o u t by t h e d e t e r i o r a t i o n p r o c e s s e s develop slowly, s o t h e i r manifestation in productivity i s delayed. This generality i s n o t valid in t h e

case

of amelioration, when improvement i s immediate.

CULTIVATION PRACTICE

Cultivation p r a c t i c e (input) determines t h e a c t u a l productivity

at a

p a r t i c u l a r soil f e r t i l i t y level, b u t i t a l s o influences t h e soil f e r t i l i t y itself, though t h i s e f f e c t i s d e t e c t a b l e only later.

Input groups

are

as follows:

-

mechanization,

-

irrigation,

-

chemicalization,

-

production pattern,

-

amelioration,

-

by-product recycling,

-

animal production.

Mechanization through technological level

t e r m

expresses how i t i s used.

From this last aspect finer categorization might have, eg.:

-

t h e quite generally used non-sustainable type which is followed by a decline in soil fertility,

-

sustainable type, which prevents soil degradation.

I r r i g a t i o n level speaks f o r itself.

Chemicatization includes both plant nutrition and plant protection. W e

em-

phasize h e r e t h a t in chemicalization what i s important is not only t h e nutritional aspect, but also t h e application method, since many disadvantages of t h e practice a r e due t o this.

P r o d u c t i o n p a t t e r n deals with c r o p rotation, vegetation cover of slopes,

etc.

Ametioration covers those actions t h a t improve soil fertility, but i s not t h e same as t h e so-called general agrotechnics. Occasionally, ameliration requires a significant degree of investment. Hydro-regulation, chemical amelioration of soils, reclamation of salt-affected soils,

etc.,

belong

to

this category.

The effect of a n i m a l p r o d u c t i o n i s changing. Extensive (grazing) animal hus- bandry significantly affects lands that a r e sensitive

to

desertification (overgraz- ing), while intensive animal husbandry affects t h e c r o p production s t r u c t u r e and contributes

to

t h e nutrient supply of c r o p production, but because of t h e concen- t r a t e d manure production i t can b e a source of environmental pollution (nitrifica- tion of groundwaters, eutrophication).

By-product recycting affects t h e organic matter content of soils. Utilization of by-products as fodder o r energy c a r r y e r increases land productivity.

OTHER FACTORS

Among o t h e r f a c t o r s I consider those t h a t affect significantly t h e soil fertili- ty, t h e productivity of regions through soil properties, and t h e type of land use.

Now w e consider

t w o

illustrative examples:

-

water management,

-

pollution.

Irrigation and hydroregulation can significantly affect c r o p production e i t h e r directly o r indirectly. Building a water r e s e r v o i r , f o r example, may directly im- prove t h e conditions of irrigation, but a t t h e same time it can raise t h e groundwa-

ter

table in t h e neighborhood, thus increasing t h e danger of secondary salinization o r wetland formation. Also, t h e expansion of industrial

water

consumption lessens t h e amount of

water

used f o r agriculture. Industrial pollution can affect surface

waters

t o such a degree t h a t r i v e r s become unsuitable f o r irrigation.

Pollution i s a very broad category. Toxic elements can r e a c h cultivated lands by

-

acid rain,

-

plant protection,

-

e x h a u s t g a s of cars,

-

a t m o s p h e r e

-

communal and industrial

waste

waters, sludges, and o t h e r wastes.

A r e c e n t major environmental problem i s t h a t caused by acid r a i n in highly in- dustrialized regions. The d e t e r i o r a t i o n i s significant in f o r e s t s and i t c a n b e as- sumed t h a t , a f t e r a while, acid r a i n will a l s o c a u s e a significant loss in c r o p pro- duction.

The mechanism of toxicity h a s not y e t been discovered, b u t i t i s known t h a t toxicity p r e v e n t s biomass formation and, a f t e r e n t e r i n g t h e food chain through plants, i t i s inherently dangerous t o human beings.

A summary of t h e f a c t o r s t h a t influence production and f e r t i l i t y i s given in Table 3. The

"+"

sign indicates a s t r o n g e f f e c t on soil f e r t i l i t y , o r in a b r o a d e r sense, o n production. The e f f e c t c a n b e e i t h e r positive o r negative. The

"-"

sign in- d i c a t e s no significant e f f e c t . The last column of Table 3. shows t h e environmental impacts o t h e r t h a n soil f e r t i l i t y , e.g., nitrification of groundwaters and eutrophi- cation of f r e s h

waters.

These problems are important with r e s p e c t t o t h e Biosphere Program, since t h e y are r e l a t e d t o f u t u r e p e r s p e c t i v e s of "life quality".

5. Functioning

o f the land-use m o d e l o f the B i o s p h e r e

Program

The introduced definitions and relationships h a v e s e n s e only if t h e y c a n b e organized into o n e , functioning system, a n example of which w e give below.

The Biosphere model is d i r e c t e d by s c e n a r i o s designed by scientific e x p e r t s , decision makers,

etc.

These s c e n a r i o s d e s c r i b e t h e main socio-economic p r o c e s s e s and r e s o u r c e utilization policies, e.g., population changes by regions, e n e r g y con- sumption, p r o d u c t distribution, technical development,

water

consumption,

etc.

Be- s i d e s t h e s e g e n e r a l a r e a s , t h e s c e n a r i o s determine activities t h a t d i r e c t l y regu- late t h e d i f f e r e n t components of t h e b i o s p h e r e , which in t h e case of land are:

-

land utilization,

-

g e n e t i c development,

-

climate change,

-

cultivation p r a c t i c e , a n d

-

o t h e r e f f e c t s (water management, pollution).

Based o n t h e above, t h e system functions as i s shown in Figure 7.

The land model i s a simulation model. In t h e f i r s t r u n i t calculates t h e a c t u a l production of mosaics by using a c t u a l inputs and soil f e r t i l i t y values; additionally, i t determines t h e changes in soil f e r t i l i t y and environmental impacts by regions.

The change in soil f e r t i l i t y i s r e f l e c t e d in t h e modification of t h e c u r v e shown ear- l i e r in Figure 3.

Environmental impacts include t h e impacts of o t h e r actions on t h e elements of t h e biosphere, b u t t h e s e are not formulated yet. After t h e s e modifications, t h e simulation p r o c e e d s t o t h e next, ( t + l ) t h , time period description.

The r e s u l t s of t h e s c e n a r i o analyzed are given in t e r m s of t h r e e p a r a m e t e r s :

-

change in production,

-

^change in f e r t i l i t y ,

-

environmental impacts.

Figure 7: Functioning of the system Scenario describing the development of the period under discussion Atmosphere Land use Water Genetic development Biota model Climate Cultivation'practice Other impact d Soil fertility

-

- - - Soil fertility Land model period t b b Environmental impact I I v 1 Actual production

Of primary importance i s production, because decision makers c a n b e d i r e c t l y influenced by it. A change in production c a n only b e i n t e r p r e t e d by t h e analysis of soil f e r t i l i t y , from which one c a n establish t h e e f f e c t t h a t caused a n unfavorable change and find o u t how t h e s c e n a r i o should b e modified t o eliminate t h a t . When building t h e system a n i n t e r a c t i v e form would b e p r a c t i c a l s o t h a t t h e p a r a m e t e r s of s c e n a r i o s could b e changed.

By t r a c i n g environmental impacts we c a n make d i r e c t conclusions as t o chang- ing of life conditions, which c a n have a feedback on r e s o u r c e management. F o r ex- ample, t h e nitrification of ground

water

may r e a c h a level such t h a t no drinking

water

i s available from n a t u r a l s o u r c e s , in which case t h e purification of

water

would r e q u i r e enormous e f f o r t s and r e s o u r c e s .

References

[I] Brown, L.R., Wolf, E.C., 1984. Soil Erosion in t h e World Economy, World Watch P a p e r 60

[2] Council on Environmental Quality and Department of S t a t e . 1980. Global 2000 Report t o t h e President: Entering t h e Twenty-first Century.

Washington, D. C.: U. S. Government Printing Office.

[3] Csaki, Cs., Harnos, Zs., Lang, I., 1984. Agricultural Development and Ecologi- cal Potential: The Case of Hungary, Kieler Wissenschaftsverlag Vauk

[4] Guidelines f o r t h e Control of Soil Degradation, 1983. FA0 and UNEP, Rome [5] Kovda, V.A., 1974. Biosphere, Soils and t h e i r Utilization, (10th International

Congress of Soil Scientists) Moscow

161 Munn, R.E., Kairiukstis L., Clark W.C., 1985. Sustainable Development of t h e Biosphere: Managing Interactions of t h e Global Economy and t h e World En- vironment. A Research Proposal Submitted by IIASA

[7] Simons, I.G., 1981. The Ecology of Natural Resources, Edward Arnold, London [8] Pusztai, A., Rajkai, K., 1982. Preliminary version of t h e soil submodel in t h e

Hungarian Task 2 c a s e study. Budapest. Manuscript.