Why Do Agroforestry Systems Enhance Biodiversity? Evidence From Habitat Amount Hypothesis Predictions

Mário Santos,Wully Barreto Da Silva,Daniel Ferreira,Maria Rosa Mosquera-Losada,Berta Gonçalves,Pedro Leote,Darinka Gonzalez,Alis-Luciana Petrescu Bakış,João Alexandre Cabral,Reinaldo Lucas Cajaiba,Rita Bastos

doi:10.3389/fevo.2021.630151

Abstract

Considering the present ecological crisis, land use-biodiversity relationships have become a major topic in landscape planning, ecosystem management and ecological restoration. In this scope, consistent patterns of outstanding biodiversity have been identified in agroforestry systems within diverse biogeographic regions and types of management. Empirical work has revealed that agroforestry higher structural complexity, when compared with current simplified agricultural systems, might be partially responsible for the observed patterns. The recently developed Habitat Amount Hypothesis predicts diversity for a local habitat patch, from the amount of the same habitat within the local landscape. We have expanded the previous hypothesis to the landscape level, computing the influence of the dominant land uses on the diversity of coexisting guilds. As a case study, we have considered archetypal landscapes dominated (or co-dominated) by crops or trees, which were compared using normalized diversities. The results obtained show that agroforestry systems substantially increase functional diversity and overall biodiversity within landscapes. We highlight that the normalized values should be parametrized to real conditions where the type of crop, tree and agroecological management will make a difference. Most importantly, our findings provide additional evidence that agroforestry has a critical role in enhancing biodiversity in agricultural landscapes and, in this way, should be regarded as a priority measure in European Agri-environmental funding schemes.

Highlights

Farming systems should be recognized from the crops’ production perspective, and from the regulating and cultural services standpoint (Plieninger et al, 2019)
All Biodiversity was condensed within a single partition in Agriculture and Forest landscapes, Normalized crop biodiversity (N_C_B) and N_F_B, respectively, and spread within all guilds (N_C_B, Normalized tree biodiversity (N_T_B), Normalized Edge Biodiversity (N_E_B)) for Clumped, Linear and Random landscapes (Figures 2A–C)
As expected (e.g., Fahrig, 2013; Torralba et al, 2016), higher Normalized crop biodiversity (N_C_B) and Normalized tree biodiversity (N_T_B) values were attained within monospecific landscapes, Agriculture and Forest correspondingly, and both landscapes low overall biodiversity’ predictions (Normalized biodiversity, Normalized Biodiversity (N_B)) (Figure 2 and Table 2)

Summary

Introduction

Farming systems should be recognized from the crops’ production perspective, and from the regulating and cultural services standpoint (Plieninger et al, 2019). In Europe, the Common Agricultural Policy (CAP) encouraged the specialization of agriculture and forestry systems in the most productive areas and abandonment of marginal (less productive) regions (De Roest et al, 2018; Santos et al, 2018; Abson, 2019). This was especially noticed in southern Europe, where CAP supporting schemes (including Agri-environmental measures) promoted relevant socio-ecological change but were unable to halt biodiversity loss and stop ecosystem services’ degradation (Harlio et al, 2019; Pardo et al, 2020). Multifunctional benefits of introducing trees in arable lands, novel silvopastoralism techniques and the maintenance and/or improvement of already existing agroforestry practices were recently discussed and added to the European Union Green Deal

Methods

Results

Discussion

Conclusion