General method for land use sustainability evaluation and basic indicators for agricultural land use durability

Abstract

Land use sustainability evaluation is a complex problem. In order to solve it, a nested hierarchy of the main subdomains/types of land evaluation is presented and, according to this systemic approach, a general hierarchical multilevel evaluation method is proposed. A specific component of sustainability is durability, defined as a measure of changes having constant trend over time determined by land use.
The second part of the paper focuses on basic time-related indicators for evaluating the agricultural land use durability. The main requirements that these indicators should meet are outlined and six of such indicators are defined: soil surface water erosion risk, soil humus content change risk, soil available phosphorus content change risk, soil available potassium content change risk, soil acidification risk and risk of soil and groundwater pollution with nitrates. The procedure to implement these indicators in the "DexTer" decision support system
for agricultural land management is outlined and an overall index (measure) of the agricultural land use durability is also defined.

Full text

GENERAL METHOD FOR LAND USE SUSTAINABILITY EVALUATION
AND BASIC INDICATORS FOR AGRICULTURAL LAND USE
DURABILITY1
Virgil VLAD
Research Institute of Soil Science and Agrochemistry - ICPA
Bd. Mărăşti - 61, 71331 Bucharest, Romania, E-mail: vvlad@icpa.ro
Abstract
Land use sustainability evaluation is a complex problem. In order to solve it, a nested hierarchy
of the main subdomains/types of land evaluation is presented and, according to this systemic
approach, a general hierarchical multilevel evaluation method is proposed. A specific component
of sustainability is durability, defined as a measure of changes having constant trend over time
determined by land use.
The second part of the paper focuses on basic time-related indicators for evaluating the
agricultural land use durability. The main requirements that these indicators should meet are
outlined and six of such indicators are defined: soil surface water erosion risk, soil humus
content change risk, soil available phosphorus content change risk, soil available potassium
content change risk, soil acidification risk and risk of soil and groundwater pollution with
nitrates. The procedure to implement these indicators in the "DexTer" decision support system
for agricultural land management is outlined and an overall index (measure) of the agricultural
land use durability is also defined.
Key words: land evaluation, land use sustainability, evaluation methods, land quality,
agricultural land use durability indicators.
Introduction
At present, land management should face the new pressures on land resources. The new
approaches in land management should focus not only on productivity and profitability, as in the
past, but also on evaluating the impacts of human interventions (during the land use) on specific
landscapes. Growth has often been achieved by degrading the natural resources, but this is no
longer acceptable. Increasingly it is being realised that land is a major factor in global life
support and that it has intrinsic value beyond agricultural production. Land provides global
environmental benefits, such as its role in global geochemical cycles, nutrient recycling, source
and sink functions for greenhouse gases, filtering/buffering the pollutants and
transmission/purification of water in the hydrologic cycle. There is increasing evidence that
indicators of land quality and sustainable land management should guide our actions. Land use
should be sustainable, and "land evaluation" today means "land use sustainability evaluation".
The main objective of the sustainable land management is to harmonise the two complementary
goals: providing environmental, economic and social benefits both for present and future
generations - that is maintaining and enhancing the performance/quality of the land resources
(soil, water and air). Sustainable land management determines the land use according to the
changing human needs while ensuring the long-term socio-economic and ecological functions of
the land. Sustainable land management is a knowledge-based procedure that guides the decisions
on land management toward the most feasible and cost effective options in achieving land use
intensification, particularly agricultural production, and improved environmental management.
1 Canarache A., Enache R. (eds). Proceedings of the International Conference on “Soil under Global Change – A
Challenge for the 21-st Century” (Constanta, sept.2002), vol.I, Ed.Estfalia, Bucuresti, 2005, p.43-54.

This paper presents a systemic approach for evaluating the land use sustainability, defines time-
related basic indicators for evaluating the durability of the agricultural use of land and presents
possibilities to implement these indicators in decision support systems and a way to define an
overall index (measure) of the agricultural land use durability.
1. Land use sustainability evaluation
Sustainable land use should simultaneously ensure (Smith & Dumanski, 1993; Dumanski
et.al.,1998):
- Productivity: maintaining and enhancing production/services;
- Stability-Resilience: reducing the level of production risk (security) and enhancing the
soil capacity to buffer the degradation processes;
- Protection: protecting the potential of natural resources and preventing the soil and water
quality degradation;
- Viability: economic viability;
- Acceptability-Equity: ensuring social acceptability and the access to the benefits from
improved land management.
Land use sustainability (LUS) is a measure of the extent to which the main objectives as above
defined can be met by a defined land use in a specific land unit (area of land assumed relatively
homogenous) over a stated period of time (Smith & Dumanski,1993). In fact, the object of
evaluation is the "Land-Use System": the binom of the land unit and the land use as a whole
(FAO, 1983; Vlad, 1997a, 2000, 2001). To evaluate the land use sustainability, all the above
mentioned factors should be taken into account, quantified and their influences assessed (Smith
& Dumanski, 1993; Vlad, 1997ab, 2000, 2001, 2002; WCSS, 1998; Dumanski et.al., 1998;
Motoc & Carstea, 1999). It is a wide sense/acceptance of the term of sustainability - the overall
sustainability.
In order to establish methods for LUS evaluation, it is useful to see the main subdomains or
types of land evaluation as the nested systemic hierarchy structure presented in Figure 1. Land
performance and quality are statically assessed, based on the present land status, taking into
consideration different factors and having in mind different aims: physical (technical) evaluation,
economic evaluation, social evaluation and environmental evaluation. It is to note that the
economic evaluation should use the physical evaluation results and the social evaluation should
use the economic evaluation results. Land use sustainability refers to the present levels of the
land physical, economic and social performance and environmental quality and also their lasting
in the future (durability). Of course, environmental and durability aspects may be included in the
economic and social evaluation, especially when some land uses are defined to meet a requested
level of environmental quality and land performance durability (so that, for example, the costs to
maintain in time the performance and quality are taken into account in economic/social
evaluation).
Environmental evaluation refers to the influence of the land use on the evaluated land unit (on-
site effects), but also refers to the neighbourhood: it is necessary to estimate the influence of the
evaluated Land-Use System on the neighbouring (adjacent) Land-Use Systems (off-site effects)
and also it is necessary to estimate the influence of the neighbouring Land-Use Systems on the
evaluated Land-Use System.
The new dimension introduced in LUS evaluation, the time, brings new problems: the need to
estimate the future changes of the land characteristics/qualities and also the need to establish the
confidence time limits or the time extent/level that the evaluation refers to. The changes of land
characteristics/qualities may be continuous, having a constant trend over time, or may have a
probabilistic (accidental) variability. The last type of characteristic changes is usually taken into
consideration in physical and economic evaluation (e.g. climatic variability, price/cost
variability, etc.) and durability refers only to the changes determined by land use. Consequently,
durability is a component of sustainability, defined as a measure of changes having constant
trend over time determined by land use.

Categories of Factors/Criteria
Subdomains / types of Land Evaluation
Soil fertility factors
Soil
Fertility
Evaluation
Soil
Other soil factors
Evaluation
Intrinsic
Physical
Other land factors
(climate, relief, hydrology)
Land
Evaluation
Physical
(Technical)
Economic
Land
Evaluation
Site factors
(access roads, parcel size/shape,
other infrastructure, etc.)
Site Assessment
Land
Evaluation
Land
Evaluation
Social
Land
Evaluation
(Land use
Sustainability
Economic factors
(prices, costs, subsidies, etc.)
Evaluation)
Social factors
Static
Evaluation
(land
performance
and quality)
Environmental factors
(level of pollution/degradation,
biodiversity, etc.)
Environmental Evaluation
Land Evaluation
Specific to Sustainabilty
Dynamic
Evaluation
Time-related aspects
(Durability) Durability Evaluation
Figure 1. Nested hierarchy of the main subdomains/types of Land Evaluation

2. General hierarchical method for land use sustainability evaluation
The land use sustainability (LUS), as above presented, is a measure that depends - in a very
complex way - on a large variety of factors. Generally, it synthesises the factor influence based
on an evaluation model (Figure 2).
Figure 2. General scheme of land use sustainability evaluation
Usually, it is difficult to develop an evaluation model, because of the number of factors and the
complexity of their inter-relational influences on the sustainability. Figure 3 presents a general
hierarchical/multilevel method for evaluating the land use sustainability - a systemic approach
based on the nested hierarchical structure of land evaluation (Figure 1).
Different factors that determine the LUS are represented by characteristics - measures/attributes
that can be directly measured or estimated. There are characteristics of land units (LCi) and land
uses (UCi). As well as the economic and social factors should be described by appropriate
characteristics (ECi, SCi). For LUS evaluation, the evaluation criteria (Kxi) should be defined.
They are obtained from the characteristics using a procedure based on appropriate sub-models.
The criteria may be physical and environmental (Kpi and Kenvi, inferred from land unit and land
use characteristics), economic (Keci - from economic characteristics), social (Ksi - from social
characteristics) and durability criteria (Kdi - from all characteristics, concerning time-related
aspects). The land use sustainability (S) is a measure that synthesises, based on an aggregation
sub-model, the influences of all the evaluation criteria.
In order to simplify the sub-models determining the criteria and avoid errors in their
development, FAO recommends to use "land qualities" (LQi) - complex/compound land
characteristics acting as an intermediate aggregation level of the primary land characteristics to
obtain evaluation criteria (FAO, 1976, 1983). For obtaining the land qualities, (pedo-)transfer
functions or rules or more complex sub-models may be used. It is useful to generalise the
concept of "qualities" to land use, economic and social factors (UQi, EQi, SQi) too. Many levels
of qualities may be established, as needed. The evaluation criteria (Kxi) may be seen as a higher
level of qualities.
The definition of economic criteria is based on economic characteristics/qualities, physical
characteristics/qualities/criteria and environmental criteria; the definition of social criteria is
based on social characteristics/qualities, physical and economic characteristics/qualities/criteria
and environmental criteria; durability criteria are based on all other
characteristics/qualities/criteria.
All the evaluation criteria of the same type may be aggregated in partial sustainability indices -
physical (Sp), economic (Sec), social (Ss), environmental (Senv) and durability (Sd). Finally, all
the partial sustainability indices may be aggregated in an overall index of sustainability (S).
The structure is not necessarily strict-hierarchical, that is in order to obtain an aggregated
element, an element in a certain level may be combined with elements in other levels.
The sub-models of aggregation may be implemented as a set of qualitative rules (expert-type), a
simple or complex mathematical function or a more complex deterministic (mathematical-
heuristic) model, which appropriately integrates the influences of the input elements,
irrespectively an unitary area of inter-related dependencies.
Factors
of
Land-Use System
Evaluation
Model
Land Use
Sustainability

Factors
Characteristics
Qualities Evaluation
Criteria Sustainabilities
Kenv1 Senv
Kenv2
Land LC1 LQ11 LQ21 . . .
Physical LC2 LQ12 LQ22
Factors . . . . . . . . . Kp1 Sp
Kp2
Land Use UC1 UQ11 UQ21 . . .
Physical UC2 UQ12 UQ22 Kec1 Sec
Factors . . . . . . . . . Kec2
. . .
Economic EC1 EQ11 EQ21
Factors EC2 EQ12 EQ22 S
. . . . . . . . .
Ks1 Ss
Social SC1 SQ11 SQ21 Ks2
Factors SC2 SQ12 SQ22 . . .
. . . . . . . . .
Kd1 Sd
Kd2
. . .
Figure 3. General hierarchical/multilevel method for land use sustainability evaluation
(For meaning of symbols, see the text of the chapter 2)

3. Basic indicators for agricultural land use durability evaluation
For applying the above-developed concepts, the paper aims at defining some indicators
(qualities/criteria) to evaluate the agricultural land use durability. The following targets and
requirements for these indicators are in view:
- the indicators refer to the agricultural use of land and time dimension of sustainability
(durability); they quantify the degree of the main changes of land properties determined by a
defined agricultural land use;
- only the on-site effects and the changes having constant trends are taken into consideration;
- the indicators are to be basic indicators (qualities or evaluation criteria): those that
characterise the basic processes, whose changes determine the main changes of the other
evaluation criteria (qualities, performances), and that take into consideration the main effects
of the main common land uses;
- the indicators are to be measured in a unitary way, in order to be easily compared between
them and integrated into aggregating algorithms;
- the indicators are aimed at being used in decision making, irrespective in decision support
systems, so they should be practical in use, that is they should be simple and clear, acceptable
from the viewpoint of accuracy and application cost and complexity, and should be defined
on the base of the available data or easily-obtained data.
In this respect, for the time being, the following indicators were defined in order to be
implemented into the DexTer system - a decision support system for sustainable management of
agricultural use of land (Vlad, 1998, 2001). Other durability indicators concerning other factors,
such as soil compaction, soil salinization, pesticide pollution (soil and groundwater), off-site
effects, biodiversity changes etc. are to be considered in the future.
3.1. Soil Surface Water Erosion Risk (RSE)
RSE = (SLSE / ESM) * 100 [ (t/t) % / year ] (1)
where:
SLSE : Soil Loss by Surface Water Erosion [ t / ha / year ]
ESM : Reference Edaphical Soil Mass [ t / ha ]
In Romanian Soil Survey Methodology (ICPA,1987), the Edaphical Soil Volume (ESV) is used
instead of the ESM characteristic, and the reference soil depth is 100 cm. ESV is a percent value
reported to 100 cm depth, so:
ESM = ESV * SBD * 100 [ t / ha ] (2)
where:
ESV : Edaphical Soil Volume [ (cm3/ cm3) % / 100 cm depth]
SBD : Soil Bulk Density [ g / cm3 ]
and:
RSE = SLSE / (ESV*SBD) [ (t/t) % / year ] (3)
where ESV and SBD are soil characteristics given in the usual soil survey works and SLSE is
computed using a formula of USLE type. In the DexTer system, the SLSE is determined using an
expert rule (ICPA,1987) and a modified/adapted USLA formula (Motoc & Mircea, 2002).
3.2. Soil Humus Content Change Risk (RHC)
RHC = ( ( Huf - Hui ) / Hui ) * 100 [ % / year ] (4)
where:

Hui : soil humus content at the beginning of the crop growing season [ % / 0-25 cm ]
Huf : soil humus content at the end of the crop growing season [ % / 0-25 cm ]
RHC is a negative value when the soil humus content decreases and is a positive value when it
increases at the end of the crop growing season.
In the DexTer system, Hui is assumed as known (from usual agro-chemical soil tests) and for
determining the Huf a statistical/empirical model calibrated for the Romanian conditions (Borlan
et.al.,2000) is used.
3.3. Soil Available Phosphorus Content Change Risk (RPC)
RPC = ( ( Pf - Pi ) / Pi ) * 100 [ % / year ] (5)
where:
Pi : Available phosphorus content at the beginning of the crop growing season
[ ppm / 100 g soil / 0-25 cm ]
Pf : Available phosphorus content at the end of the crop growing season
[ ppm / 100 g soil / 0-25 cm ]
RPC is a negative value when the soil available phosphorus content decreases and is a positive
value when it increases at the end of the crop growing season.
In the DexTer system, Pi is assumed as known (from usual agro-chemical soil tests) and for
determining the Pf a statistical/empirical model calibrated for the Romanian conditions (Borlan
et.al.,1996) is used.
3.4. Soil Available Potassium Content Change Risk (RKC)
RKC = ( ( Kf - Ki ) / Ki ) * 100 [ % / year ] (6)
where:
Ki : Available potassium content at the beginning of the crop growing season
[ ppm / 100 g soil / 0-25 cm ]
Kf : Available potassium content at the end of the crop growing season
[ ppm / 100 g soil / 0-25 cm ]
RKC is a negative value when the soil available Potassium content decreases and is a positive
value when it increases at the end of the crop growing season.
In the DexTer system, Ki is assumed as known (from usual agro-chemical soil tests) and for
determining the Kf a statistical/empirical model calibrated for the Romanian conditions (Borlan
et.al.,1999) is used.
3.5. Soil Acidification Risk (RA)
RA = ( ( pHi - pHf ) / pHi ) * 100 [ % / year ] (7)
where:
pHi : Soil pH at the beginning of the crop growing season [ / 0-25 cm ]
pHf : Soil pH at the end of the crop growing season [ / 0-25 cm ]
RA is a positive value when at the end of the crop growing season a soil acidification process
occurs and it is a negative value when a soil alkalisation process occurs.
In the DexTer system, pHi is assumed as known (from usual agro-chemical soil tests) and for
determining the pHf a statistical/empirical model calibrated for the Romanian conditions
(Gavriluta et.al.,1997) is used.

3.6. Risk of Soil and Groundwater Pollution with Nitrates (RNP)
RNP = ( NL / NMax ) * 100 [ % / year ] (8)
where:
NL : Amount of nitrates leached under root zone during the crop growing season
[ kg / ha / year ]
NMax : Amount of maximum acceptable Nitrates in Soil & Groundwater [ kg / ha ]
NL can be determined using an appropriate crop simulation model. In the DexTer system, the
IMPEL model (Rounsevell et.al.,1998) and STICS model (Brisson et.al.,1998) are planned to be
used.
3.7. Overall Index of Agricultural Land Use Durability (Sda)
Sda = f (RSE, γSE, RHC, γHC, RPC, γPC, RKC, γKC, RA, γA, RNP, γNP, ... ) [ % ] (9)
where:
RXX : Risk Indicators [ % / year ]
f : Algorithm implementing a Multiattribute Multicriterial Decision Method
(methods developed in the operational research mathematics,
e.g. the Wald, Laplace, Hurwitz, Savage, ELECTRE methods, etc.)
γXX : Weighting Coefficients appropriate to the decision method.
In the DexTer system, more multiattribute multicriterial decision methods are planned to be
implemented, so as the decision makers have the possibility to choose the appropriate method
and coefficients according to the aim of the analysis/evaluation/decision, irrespective according
to the problem to be solved (Vlad, 2001).
For example, considering the simpliest decision method (weighting average) and defining
durability as the annual probability to maintain the six land qualities at the end of the crop
growing season with the same level as at the beginning of the crop growing season:
Sda = 100 - (RSE* γSE - RHC* γHC - RPC* γPC - RKC* γKC + RA* γA + RNP* γNP) [ % / year] (10)
where:
Σ γXX = 1 (11)
Conclusions
• For evaluating the land use sustainability (LUS), a great number and a great complexity of
factors should be taken into consideration. The object of evaluation should be the Land-Use
System - the binom of the land unit and the land use as a whole. In order to establish methods
for LUS evaluation, it is useful to see the land evaluation as a nested hierarchical structure
(Figure 1): soil fertility evaluation - soil evaluation - intrinsic physical land evaluation -
physical land evaluation - economic evaluation - social evaluation - land (LUS) evaluation.
• For LUS evaluation, it is needed an evaluation model which is difficult to be developed due
to the number of factors and the complexity of their inter-relational influences on the
sustainability. A practical way to determine the LUS is the hierarchical/multilevel method
(Figure 3) - a systemic approach based on the nested hierarchical structure of land
evaluation: evaluation factors - characteristics - qualities - criteria - partial sustainability -
sustainability.
• For decision making in the agricultural practice, many indicators are necessary for evaluating
the time-related aspects of sustainability of a land use (agricultural land use durability). They

should be defined appropriately (specifically) to the aim of evaluation. However, some basic
indicators may be used in more evaluations. These indicators should be defined to quantify
the main changes of the land characteristics and to be practical in use (simple, clear and
acceptable from the viewpoint of accuracy, complexity and data used in application).
• In many cases, for estimating/determining the LUS indicators, it is feasible to use more
accurate available algorithms or models instead of a direct simple formula.
• Sometimes an overall index for LUS is necessary. It should be specific to the aim of
evaluation. The Multi-Attribute Multi-Criteria Decision Method is a practical and acceptable
way for estimating such index. This is a general method that can be also used for aggregating
different heterogeneous indicators into a higher-level evaluation indicator in the evaluation
hierarchy. For that, it is advantageous that the heterogeneous indicators have a unitary
measuring way (such as normalisation as percentage indices).
• To evaluate the LUS, appropriate computer software is necessary, which has to implement
different algorithms and models for estimating/determining various compound characteristics
of Land-Use Systems and different sustainability indicators, and aggregate indices for
different aims. The integration of such software into a Decision Support System for
Sustainable Land Management is advantageous.
• Besides the indicators defined in this paper for the agricultural land use durability, other
important factors should be included into a decision support system for sustainable land
management: soil compaction, soil salinization, pesticide pollution (soil and groundwater),
off-site effects, biodiversity changes, etc.
• More research is needed in order to establish/define different important indicators,
algorithms, models, thresholds, weighting coefficients, etc. for different purposes of LUS
evaluation.
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