Diversity buffers agricultural yield under variable environmental conditions

Background/Question/Methods

Global climate change is expected to increase climatic variation, resulting in a higher frequency of extreme conditions. This has important implications for agroecosystems, as weather extremes greatly reduce agricultural production. Plant diversity has the potential to increase plant productivity and ecosystem stability through a variety of mechanisms, including complementary use of resources, reduction of intraspecific competition and decreased frequency of pest outbreaks. To investigate the potential of agricultural biodiversity to buffer against climate change, we examined the relationship between planned plant diversity and yield as a function of climate variability.  We performed a meta-analysis, identifying studies performed in the US that compared crop yield in monoculture and polyculture and quantified climatic variability for the location and time period of each study. Initial searches returned 137 peer-reviewed papers that met our selection criteria. For each study we calculated a log-response ratio of yields from polyculture and monoculture treatments. To estimate climatic variability within each study we gathered local climate data from NOAA and calculated precipitation and temperature variability for the given experimental site.  We also used agricultural insurance claim records from the USDA Risk Management Agency as a proxy for crop damage due to weather events.

Results/Conclusions

Preliminary results show that under conditions of increased precipitation variability crops grown in polyculture have higher yields than crops grown in monculture. Variability in temperature appears to have less influence on the relative performance of polyculture and monoculture yields. In years with more insurance claims, the focal crop produced relatively more yield in polycultures of both additive (p<0.05) and substitutive design (p<0.01) than the focal crop did in corresponding monocultures.  

This study is among the first to show how crop diversification may play an important role in mitigating effects from extreme weather events that are predicted to occur with global climate change. Futhermore, our study provides support for a positive relationship between plant species richness and stability relationships in a broader ecological context. Previous studies have reported greater productivity or biomass production with increased diversity at the community level. While specific mechanisms cannot be identified with our study, our results suggest that crop diversification may provide increased resiliency to crop production at the species level.