The PEDA model:the ECA’s contribution to modelling Population-Environment-Development-Agriculture interactions

The Commission has developed an interactive computer simulation model to illustrate the interactions between population changes (P), the environment (E), socio-economic development (D) and agriculture (A). The PEDA model is an advocacy tool to illustrate the likely impact of alternative policy options on the food security status of the population. As food security is a factor of developments in the areas of population, environment, agriculture and socio-economic development, the model demonstrates the relationships between these fields as well. Recently, an HIV/AIDS component has been introduced to account for its impact on both agricultural and human development variables. As such, the PEDA model is capable to provide indicative answers to a wide range of development related policy questions (box1).

The simulation exercise in PEDA consists of three steps. First, (multi-state) population projections are carried out to determine the size and characteristics of the population. Simultaneously, the model estimates the food availability as the sum of food production and net trade. Agricultural production is considered as factor of the natural resources stock (land and water); the size and productivity of the labour force (endogenously determined by the model through the population projections) and technological inputs and innovations in agriculture. In a third step, the estimated available food is distributed over the population following a non-linear food distribution curve to determine the fraction of the population that will be food insecure. 

The theoretical inspiration for PEDA comes from the “vicious circle model” that was originally developed by Partha DasGupta (Cambridge University) and others. The vicious circle assumes a causal chain of interactions between poverty, high population growth, environmental degradation and decreasing per capita agricultural production (see box 2). The vicious circle can be broken through several possible interventions in the field of food production, food distribution, education, environmental protection and population dynamics. The objective and advantage of a quantitative model like PEDA is to help users and policy makers to think in terms of the outcomes of alternative policy scenarios and, most importantly, to consider the nexus issues within a holistic framework.    

Central, or characteristic to the PEDA model is its population or human development based approach. It views human beings and their characteristics (education, health status, food security status and place of residence) both as the agents of social, economic, cultural and environmental change and as those who are the first at risk suffering (or benefiting) from repercussions of these changes. The economic environment (e.g. the importance of markets in distributing goods) plays only an intermediate role and is not seen as an end in itself nor the primary objective of the modelling exercise. In this, the population-based approach differs from much of the development economics literature.

To date, the PEDA model has been initialised for Burkina Faso, Botswana, Cameroon, Ethiopia, Madagascar, Mali, Nigeria, Uganda and Zambia. The data for three of these countries have been prepared as part of a two week training of FSSDD staff at the International Institute for Applied Systems Analysis.

The year 2000 has been an important year in the development of the model. After the first rounds of review by African and international scientists and professionals, the model has been adapted and improved to incorporate suggestions from scientists in different fields and the model has been made more flexible. It, for example, has been generalized (to allow for other theoretical assumptions than the vicious cycle model), it has been made time independent (to allow for the replication of history) and a shell has been developed to make the software independent from the data. Additionally, some refinements have been made in the software and new output variables were introduced.

A technical and users manual to accompany the distribution of the software are being finalized, and some advocacy booklets that support the ECA’s mission of awareness creation on the nexus issues are under preparation as well. The ECA also started carrying the model to the sub-regional level through the organization of workshops for policy makers and researchers at the Sub Regional Development Centers (SRDC’s). As a potential offshoot of these sub-regional workshops, the ECA will support initiatives from universities and research institutes to collect country specific data, to customize the model to reflect the situation at the national level and to carry out sensitivity analyses.

The PEDA model was developed with the assistance of Drs. W. Lutz and S. Scherbov of IIASA.  

For more information on the PEDA model contact the Food Security and Sustainable Development Division, Economic Commission for Africa, PO Box 3001, Addis Ababa, Ethiopia, fax: +251 1 51 44 16, e-mail: peda@uneca.org