Perennial Forage Systems Enhance Ecosystem Quality Variables Compared with Annual Forage Systems

There is an intense argument about the environmental impact of annual vs. perennial forage production systems. In this study, a systematic review was employed to obtain 47 empirical studies from 13 published papers between the years 2017–2023 to help clarify the issue. The objective of this study was to determine how perennial and annual forage (business-as-usual, BAU) production systems affect dry matter yield (DM) and energy of production including specific environmental impact variables. Impact variables were classified into three main groups: human health, ecosystem quality, and resource consumption. Net energy of lactation (NEL) was considered as a functional unit. Overall, perennial forage production systems varied less in DM yield and energy production than annual monocrop systems, indicating stability in perennial production. There was no statistically significant difference in human health and resource consumption variables between perennial and annual forage production systems, except for ozone layer depletion potential. However, perennial forage systems significantly lowered variables within the ecosystem quality category. Ecotoxicity potential decreased by two and 18 times compared with BAU—control (only annual monoculture forages), and BAU—improved (any annual cropping system other than BAU—control), respectively. Perennial forage systems showed a significant effect size of −8.16, which was slightly less than the effect size of the BAU—improved system but two times less than BAU—control in terms of terrestrial acidification potential. While BAU—control showed an insignificant effect size in relation to eutrophication potential (EUP), perennial forage systems reduced EUP by approximately five and two times compared with BAU—control and BAU—improved, respectively. Therefore, this study highlights the importance of promoting perennial forage production system to foster resilience and stability in DM yield and energy production, with improvements in environmental human health (ozone layer depletion potential) and ecosystem quality variables.