Northern Atlantic Zone Research Articles

A goal-oriented approach to identify and engineer land use systems

This paper describes a formalized approach to identify and engineer future-oriented land use systems. Such land use systems can be used to explore options for strategic decision making with respect to land use policy and to do ex-ante assessment of land use alternatives to be further tested or developed in experimental settings. The so-called goal-oriented approach consists of three steps: (1) goal-oriented identification and design of land use systems; (2) quantification of biophysical production possibilities; and (3) defining the optimal mix of inputs, i.e. the production technique, required to realize production possibilities. The goal-oriented identification and design depends on the land-related objectives of a system under study, whereas plant, animal and environmental characteristics determine biophysical production possibilities. Characteristics of the production technique determine the realization of production possibilities. General guidelines are given to structure the specification and number of alternatives to be explored and to apply agro-ecological principles required for quantification of future-oriented land use systems. Concepts of the approach are illustrated with data from the northern Atlantic zone of Costa Rica and the Sudano–Sahelian zone of Mali. Finally, suggestions are given for the application of the approach at spatial and temporal scales exceeding the field level and time horizon of 1 year.

Uncertainty in technical coefficients for future-oriented land use studies: a case study for N-relationships in cropping systems

Engineering of land use systems for policy-oriented future studies and the development of new farming systems requires various information sources. Often, both process knowledge and data are subject to uncertainty that affects quantification of land use systems in their inputs and outputs. This paper analyzes the effects of uncertainty in three important N-relationships relevant for quantification of future-oriented cropping systems: (i) N-leaching as function of crop characteristics, (ii) N-concentration as function of yield level, and (iii) the recovery of crop residue-N. Based on verifiable assumptions, uncertainty in these three N-relationships is specified in terms of N-loss and production costs of cropping systems. Data and process knowledge as applied in LUCTOR, a summary model to design and quantify inputs and outputs of cropping systems for the northern Atlantic zone of Costa Rica, are used as a case study. All three relationships and their uncertainty have a major impact on N-loss of cropping systems, while effects on costs are limited and depend on the share of costs for fertilizer management in total production costs. Analyses as presented explicitly specify uncertainty of process knowledge and data used in future-oriented studies. Therefore, such analyses enable a better management or reduction of uncertainty through the identification of cropping systems with smaller uncertainty margins, and identification of research aimed at a more complete understanding of involved processes.

Regional analysis of soil-atmosphere nitrous oxide emissions in the Northern Atlantic Zone of Costa Rica

Summary Regional analysis of greenhouse gas emissions is becoming increasingly important in answering questions related to environmental change, and typically employs a Geographic Information System (GIS) linked with a process-based simulation model. For the Northern Atlantic Zone (NAZ) in Costa Rica (281 649 ha), a regional analysis of soil–atmosphere nitrous oxide fluxes from the dominant land-use types forest, cattle pastures, and banana plantations was performed with both deterministic and stochastic variable representations. The stochastic representation accounted for soil and land management variability across nongeoreferenced fields within 1572 georeferenced land units in 13 relevant classes. Per class, frequency distributions of field-scale fluxes were simulated with a process-based model and Monte Carlo methods. Stochastic incorporation of both soil and land use variability resulted in areal (i.e. land unit-scale) fluxes that were 14–22% lower than estimates based on averaged inputs. Soil heterogeneity was dominant. In addition, spatial flux patterns for current (1992) land use and two alternative land-use scenarios were evaluated using stochastic inputs. With current management, the regional nitrous oxide-N flux (standard deviation in parentheses) from agricultural land was 0.43 (0.13) Gg y−1. Replacing natural grasses with mixtures of grasses and N-fixing species on relevant soil types and introducing different forms of banana plantation management (alternative I) increased the regional flux by 51% to 0.65 (0.22) Gg y−1. When all natural grasses were replaced by fertilized improved species and allowing different forms of banana plantation management (alternative II), the regional flux increased by 126% to 0.97 (0.68) Gg y−1. Using the revised IPCC methodology, the 1992 nitrous oxide emission from agriculture in the NAZ was estimated to be 0.32 Gg y−1. Due to formidable data requirements, regional analysis may not easily be used to produce country-level estimates. However, regional analysis does provide a valuable benchmark against which the more straightforward IPCC methodology can be evaluated.

Quantification of land use systems using technical coefficient generators: a case study for the Northern Atlantic zone of Costa Rica

This paper describes two generic so-called technical coefficient generators, PASTOR (Pasture and Animal System Technical coefficient generatOR) and LUCTOR (Land Use Crop Technical coefficient generatOR), that quantify land use systems in terms of inputs and outputs based on the integration of systems-analytical knowledge, standard agronomic and animal husbandry data and expert knowledge. PASTOR quantifies livestock systems while LUCTOR is geared towards cropping systems. Main inputs quantified include costs, labour requirements, fertiliser use and application of crop protection agents. Outputs are production and a number of associated environmental indicators. Although both PASTOR and LUCTOR were developed to generate input data for land use models, they are also useful as stand-alone tools to explore the technical efficiency of land use systems, to perform cost-benefit analyses and to quantify the trade-off among socio-economic, agronomic and environmental indicators at the field level. PASTOR and LUCTOR are illustrated with data from the Northern Atlantic zone in Costa Rica. Tools such as PASTOR and LUCTOR integrate different types of knowledge, including non-documented knowledge from field experts and make that knowledge transparent and open to critical review and discussion by others.

A framework for integrated biophysical and economic land use analysis at different scales

There is a general need for quantitative tools that can be used to support policy makers in regional rural development. Here, a framework for (sub-) regional land use analysis is presented that quantifies biophysical and economic sustainability trade-offs. The framework, called sustainable options for land use (SOLUS), was developed over a 10-year period of investigation in the Northern Atlantic Zone of Costa Rica and encompasses scale levels that range from field to region. SOLUS consists of technical coefficient generators to quantify inputs and outputs of production systems, a linear programming model that selects production systems by optimizing regional economic surplus, and a geographic information system. Biophysical and economic disciplines are integrated and various types of knowledge, ranging from empirical expert judgement to deterministic process models are synthesized in a systems-analytical manner. Economic sustainability indicators include economic surplus and labor employment, and biophysical ones include soil N, P and K balances, biocide use and its environmental impact, greenhouse gas emission and nitrogen leaching loss and volatilization. Land use scenarios can be implemented by varying properties of production inputs (e.g., prices), imposing sustainability restrictions in the optimization, and incorporating alternative production systems based on different technologies. Examples of application of SOLUS in the Northern Atlantic Zone of Costa Rica show that introduction of alternative technologies may result in situations that satisfy both economic as well as biophysical sustainability. On the other hand, negative trade-offs were found among different dimensions of biophysical sustainability themselves.

Quantifying economic and biophysical sustainability trade-offs in tropical pastures

Sustainability of tropical pastures has various economic and biophysical dimensions and is affected by species composition, age and management. The sustainability of pastures in cattle ranching systems was analyzed in terms of economic viability, soil nitrogen stock change, CO 2 loss/sequestration, N 2O and NO emissions, pollution by herbicides, and nitrogen leaching loss, for a case study in the Northern Atlantic Zone of Costa Rica. Development scenarios were explored for the next 25 years based on degradation and yield decline of current pastures, and on possible introduction of grass–legumes and fertilized improved grass species. With degradation of current pastures, gross margin, soil nitrogen stock, nitrogen leaching and N 2O and NO emissions are simulated to decrease in time, whereas CO 2 emission and herbicide use increase. With the introduction of grass–legumes or fertilized grasses, the reverse takes place. The conversion of degraded pasture to grass–legumes or fertilized grasses is calculated to lead to a sequestration of CO 2 of up to 50 ton C ha −1, which might be a potential mechanism in mitigating the greenhouse effect. Quantitative, exploratory studies point out the often conflicting nature of different dimensions of sustainability and show possible pathways of sustainable development.

Modeling Nitrogen Oxide Emissions from Current and Alternative Pastures in Costa Rica

AbstractEmissions of nitrogen (N) oxide were simulated for one current, unsustainable pasture management system (Natural) and two alternative, sustainable systems (Grass‐Legume and Fertilized Improved) relevant to the Northern Atlantic Zone (NAZ) of Costa Rica. To produce frequency distributions of N oxide emissions, an expert system for generating technical coefficients of pastures was linked with a process‐based simulation model. The expert model generated parameter sets representing different options for the three management systems. The simulation model was rerun for each parameter set. Simulated nitrous oxide (N2O)‐N losses 25 yr after pasture establishment were 3 to 5 kg ha−1 yr−1 for natural pastures, 12 to 15 for grass‐legume mixtures, and 7 to 28 for fertilized grasses. Losses of nitric oxide (NO)‐N were 1 to 2 kg ha−1 yr−1 for natural pastures, 7 to 8 for grass‐legume mixtures, and 3 to 16 for fertilized grasses. Stepwise multiple regression showed that N2O‐N losses were explained by annual C input to the soil (R2 = 0.997), and NO‐N losses by attainable dry matter production (R2 = 0.972). Carbon input and dry matter production were controlled by stocking rate and fertilizer level. Soilatmosphere N oxide emissions from pastures may increase by a factor 3 to 5 when natural pastures are converted to improved pastures. Such conversion may increase the sustainability of the pasture by stopping the decline of soil N. However, the change is not necessarily sustainable from a global perspective because it increases the emission of N oxide greenhouse gases.

Quantifying economic and biophysical sustainability trade-offs in land use exploration at the regional level: a case study for the Northern Atlantic Zone of Costa Rica

A generic methodology is presented for exploration of sustainable land use options at the regional level by quantifying trade-offs between socio-economic and biophysical sustainability objectives. The methodology is called SOLUS (Sustainable Options for Land USe), and was developed over a ten year period of investigation in the Northern Atlantic Zone of Costa Rica. SOLUS includes a linear programming model, technical coefficient generators for livestock and cropping activities and a geographic information system. The linear programming model maximizes regional economic surplus subject to a flexible number of resource and sustainability constraints. Economic sustainability indicators are economic surplus and labor employment, and biophysical ones include soil N, P and K balances, pesticide use and its environmental impact, nutrient losses and a proxy for trace gas emissions. The capabilities of the methodology are illustrated for the Northern Atlantic Zone of Costa Rica. Though ample scope exists for reducing environmental effects and introducing sustainable production systems separately, pursuing both objectives simultaneously, considerably reduces economic surplus and agricultural employment. Agricultural area can be decreased and forested area increased without severely affecting the regional economic surplus.