LEOPOLD MATRIX: WHAT IS IT FOR, ADVANTAGES, EXAMPLES - ENVIRONMENT - 2025

The Leopold matrix is a double-entry table of cause-effect relationships used in environmental impact assessment. This matrix systematizes the relationship between the actions to be implemented in the execution of a project and their possible effect on environmental factors.

The Leopold matrix is ​​widely used as a qualitative evaluation method and allows to assign a character to the impact (positive or negative). This matrix method of evaluation was proposed in 1971 by Luna Leopold in collaboration with other North American researchers.

Environmental impact of an industrial complex in Huelva, Spain. Source: Calapito

Among its main advantages are being a simple method to implement, low cost and applicable to all types of projects. The main disadvantage is the subjective burden on the researcher's decisions when assigning orders of magnitude and importance.

On the other hand, this method only considers primary impacts of linear interaction, not complex interactions between actions, environmental factors or secondary repercussions.

Since its creation, it has been applied in numerous environmental impact studies in various fields such as mining, construction, aquaculture and agriculture.

What is it for?

The Leopold matrix is ​​used to assess the possible environmental impact of project execution and was initially developed for mining projects. This method is useful as it is a checklist that uses qualitative information on cause and effect relationships.

In the environmental laws of the world, environmental impact studies are required to approve projects of various kinds, such as the construction of roads, urban planning, industrial plants, mining, oil, or any activity likely to affect the environment.

The Leopold matrix is ​​a simple method that allows a first holistic approach to the definition of possible environmental impacts.

How is built?

Matrix structure

When the matrix begins to be elaborated, in the first row (upper part) the actions to be executed in the project to be evaluated are placed. At the extreme left (first column) the environmental factors that can be affected by each action are noted.

In the cells formed by the intersection between rows and columns, the magnitude and importance of the impact are noted. The final columns show the totals for the number of positive and negative impacts and the impact for each environmental factor. In the last rows, positive and negative impacts and the impact for each action are noted.

Matrix of interaction between environmental factors and actions. Source: self made.

Finally, in the lower right corner the result of the total sum of impacts of actions and that of factors is noted. Both figures must be identical and indicate the level and type of impact (negative or positive).

Calculation of the impact value in the Leopold matrix

Actions, factors and their interaction

For Leopold's matrix, 88 environmental factors or components and 100 possible actions to consider are suggested. Therefore, the potential impacts or interactions to be evaluated are 8,800.

Depending on the evaluated project, the researcher selects the environmental factors and actions that he considers and can add some specific ones. When an interaction between an environmental factor and an action is relevant, a diagonal is drawn in that cell.

Impact assessment matrix. Source: self made.

The sign, magnitude and importance of the impact

The values ​​of the magnitude of the impact and the value of its importance have been pre-established in reference tables. From these tables, the researcher takes the values ​​according to his criteria.

In the reference tables, the values ​​of the magnitude of the impact range from + 1 to +10 if the impact is positive. When the impact is evaluated as negative, values ​​between -1 to -10 are assigned.

The assessment of the importance of the impact on the environment always has positive values ​​ranging from 1 to 10.

In the cell of the selected diagonal of the interaction between an environmental factor and relevant action, two values ​​are noted. Above the diagonal the value of the magnitude of the selected impact is noted and below this diagonal the value of the importance.

Subsequently, each cell will have a single positive or negative value, as a result of multiplying the magnitude by the importance. This will be the value and sign of the impact caused by a specific interaction between an action and a given environmental factor.

Balance of the effects

In the corresponding columns, the total number of negative and positive impacts for each environmental factor is entered. In addition, the sum of the total cells for each environmental factor must be recorded.

In the same way, it is done in the corresponding rows for the total negative and positive effects of each action and the total sum.

Final assessment

All the total values ​​of the environmental factors and all the total values ​​for the actions are added, which must match. If the value obtained is negative, it is considered that the global impact caused by the project negatively affects the environment.

If positive values ​​are obtained, the project is not adversely affecting the environment. In fact, it can be concluded that the project may be favorably increasing environmental factors.

Evaluation of the results

The results obtained in the application of the Leopold matrix can be analyzed using basic statistics or graphically.

Statistic analysis

For this, the mean and standard deviation are calculated for the sums of the rows and for the columns (aggregation of impacts). Any value in a cell greater than the standard deviation and the mean is considered to affect the environment.

This specific project action must be considered for prevention or mitigation measures.

Graphical analysis

In this case, we proceed to graph the impact values ​​in Cartesian coordinates, obtaining a point cloud graph. Depending on where the points are concentrated, we will know if the impact of the project is negative or positive.

Advantage

Among the advantages of applying the Leopold matrix are:

1.- It presents in a schematic way the actions of a project and their possible effects on environmental factors, being easy to understand.

2.- It includes both the order of magnitude of the impact and the importance assigned to it.

3.- Different matrices elaborated for different alternatives in the project under consideration can be compared.

4.- It is a low-cost application methodology.

5.- It is very useful as an initial application method for a first approximation. From its results more complex studies can be planned.

6.- It is applicable to all types of projects that involve environmental effects.

Disadvantages

The following disadvantages of this methodology have been noted:

1.- Subjectivity in the definition of impacts, as well as in the assignment of magnitude and importance. This is the most important disadvantage, since the investigator makes the assignments at his discretion.

2.- It only considers linear interactions (primary effects), not complex interactions between actions or between environmental factors or secondary effects.

3.- The temporal dimension of the impact is not considered, so it does not differentiate between short, medium or long term effects.

4.- The list of actions and environmental factors can leave out elements of specific projects.

5.- It does not consider the probability of the impact actually occurring, since it assumes 100% probability of occurrence.

6.- It does not allow to highlight specific critical areas of interest.

Examples

Leopold's matrix has been widely used in environmental impact assessments since its creation in 1971. During these years, it has undergone some modifications, among which the increase in the number of factors to be considered stands out.

Mining in Colombia. Source: Lady Castro

Decision support software

The Leopold matrix has been the fundamental basis for many environmental impact assessment methodologies. We have for example the Ecozone II, a decision support system developed during the 80s of the 20th century.

This system was designed to facilitate environmental impact studies in the agriculture, agribusiness and aquaculture sectors in less developed countries.

Environmental impact assessment (EIA) in wetlands and aquaculture

An example of the application of the Leopold matrix was the EIA carried out in the marshes of Serbia in 2015.

The marshes are very fragile ecosystems and highly threatened by human activities. In this study, impacts related to urban construction and agriculture were evaluated.

Another case is in Mexico, where there are no official evaluation methods, but it is suggested to apply the Leopold matrix. For example, in this country it has been applied to assess impacts in aquaculture projects.

Environmental impact assessment in construction

In the construction of a maritime terminal for the Gas Liquefied Petroleum company in Ecuador, three environmental impact assessments were carried out based on the Leopold matrix method with different modifications. For its application, various environmental factors were taken into account:

• Physical environment: air quality, gas emissions, erosion or sedimentation, soil quality, sea water quality, drinking water.
• Biotic environment: terrestrial flora, marine flora, terrestrial fauna, marine fauna.
• Socio-cultural environment: economic activities, job creation, occupational safety and hygiene, basic services infrastructure, cultural activity, quality of life, visual quality.

References

1. Food and Agriculture Organization of the United Nations (FAO) (1996) Environmental impact assessment and environmental auditing in the pulp and paper industry (Working paper 129). Rome. Recovered from: fao.org
2. Food and Agriculture Organization of the United Nations (FAO) (2009) Environmental impact assessment and monitoring in aquaculture. FAO Fisheries and Aquaculture Technical Paper. No. 527. Rome, FAO. 57p.
3. Howells O, G Edwards-Jones and O Morgan (1998) Ecozone II: a decision support system for aiding environmental impact assessments in agriculture and rural development projects in developing countries. Computers and Electronics in Agriculture, 20 (2), 145–164.
4. Hyman EL and B Stiffel (1988) Combining facts and values ​​in environmental impact assessment. In: Theories and Techniques. Social Impact Assessment Series 16. Westview Press, Boulder, CO.
5. Kicošev V, J Romelić, A Belić, I Marinić and B Panjković (2015) Assessment of the influence of anthropogenic factors on elements of the ecological network in Vojvodina (Serbia) using the Leopold matrix. Arch. Biol. Sci., Belgrade 67: 1209-1217.
6. Leopold LB, FE Clarke, BB Hanshaw and JR Balsey 1971. A procedure for evaluating environmental impact. US Geological Survey Circular 645, Washington DC.
7. Ramos-Soberanis AN. (2004). Matrix environmental assessment methodologies for developing countries: Leopold matrix and Mel-Enel method. Degree work. University of San Carlos of Guatemala. Faculty of Engineering. School of Civil Engineering. Guatemala
8. Recalde S, M Mindiola and J Chang. (Revised 2/27/2019). Analysis of methodologies for the environmental evaluation of the construction of the maritime terminal in the Monteverde sector, Province of Santa Elena. dspace.espol.edu.ec
9. Shopley JB and RF Fuggle. 1984. A comprehensive review of current environmental impact assessment methods and techniques. Environ. Manag. 18, 25–47