Are there clear benefits from diversification of land use: a review and preliminary meta-analysis?

Diversified farming systems are often considered more resilient and environmentally sustainable than monocultures. However, their performance on key environmental and economic outcomes remains poorly defined across different contexts. We reviewed the literature and examined data from 277 sites, primarily in New Zealand, regarding the merits of land-use diversification. We tested the hypothesis that nitrogen (N) and phosphorus (P) losses to freshwater (kg/ha), greenhouse gas (GHG) emissions, and job creation differ between farm and catchment scales and that diversification can reduce these environmental losses. Our findings indicate that, contrary to expectations, N losses were higher in diversified systems compared to monocultures at farm scale, and catchment scale. This increase was largely attributed to land-use changes and cultivation practices. However, the total number of jobs was higher in diversified systems at both scales. Although heavily context-dependent, these observational data provide a rationale to determine the conditions under which diversification can improve environmental and economic outcomes. Beyond biophysical conditions, additional challenges in implementing diversification lie in the phasing and implementation of catchment policies at the farm scale, robust supply and value chains to adapt to market demands, and the need to develop and implement technology fit for varied (and diversified) farm systems.