Effect of silvopasture, paddock trees and linear agroforestry systems on agricultural productivity: A global quantitative analysis

CONTEXT

Agroforestry provides numerous benefits to agricultural landscapes, including timber production, carbon sequestration and enhanced biodiversity. Critically, agroforestry also influences the productivity of pasture, crops, and livestock. The magnitude and direction of the effect, however, is highly variable due to factors including the type of agroforestry (e.g., windbreak, alley, silvopasture), the condition of the trees (e.g., height, age, species), planting location and climatic conditions. However, currently there is limited information that quantifies how variation in these drivers affects the influence of agroforestry on agricultural yields.

OBJECTIVES

In this quantitative review we aimed to determine the magnitude of the effect that silvopasture, paddock trees and linear agroforestry systems have on agricultural productivity relative to a treeless comparison. In addition, we attempted to understand how the effect of agroforestry varied with factors such as tree condition, climate, and weather.

METHODS

A global literature review was conducted examining two key agroforestry types (non-intercropped linear systems such as windbreaks and hedges, and dispersed pasture systems such as paddock trees and silvopasture). Agricultural productivity responses of these systems compared to a treeless control were extracted and the size of the effect was compared to a range of conditions of the agroforestry systems e.g. tree density, age, distance to tree, as well as a range of climate and weather conditions.

RESULTS AND CONCLUSIONS

For the agroforestry types examined we found a strong evidence base for the effects on crop/pasture growth for linear agroforestry types (windbreaks, alleys) and on pasture growth in paddock tree/silvopasture systems (crop growth was not examined in these systems). There was limited information on the effects of linear agroforestry systems on livestock production. Linear agroforestry features were generally beneficial for crop and pasture growth. By comparison, silvopasture systems resulted in a reduction in both pasture and livestock productivity, although such systems are likely to provide other benefits for mitigating risk. Tree condition was a major factor driving effect size, the most prominent drivers being paddock size in linear configurations, and tree density in silvopasture systems. Climate variables also influenced the effect of agroforestry on productivity, indicating that both local and seasonal climate variation needs be considered when predicting effect sizes.

SIGNIFICANCE

This study provides important baseline information for valuing the effects linear and dispersed agroforestry types have on farm productivity and predicting under what conditions these effects will be optimised. Such information will aid in designing and implementing effective agroforestry systems.