We've long known that biodiversity has a stabilizing effect on productivity over time. But we haven't been quite sure whether that's during extreme events, after them, or both. This research showed that diverse communities are more stable because they exhibit resistance during extreme climate events.
In 1994 a study reported that ecosystem productivity of diverse grassland plant communities was more resilient to a major drought than that of less diverse communities. However, this study had not experimentally manipulated biodiversity, which made is very difficult to disentangle biodiversity variation and other parameters such as variation in species composition and resource availability. Unfortunately, many studies over the last two decades did not help to sufficiently answer the question whether biodiversity buffers ecosystems against climate extremes, which are becoming increasing frequent worldwide.
A new study involved more than three dozen researchers from the U.S., Germany, the U.K., Ireland, France, Switzerland, the Netherlands, Czech Republic and Japan. The researchers began by classifying each year of each experiment on a five-point scale from extremely dry to extremely wet. They then measured corresponding productivity - basically, how much above-ground plant material each level of plant biodiversity produced each year. The group did 46 experiments in which they manipulated grassland plant diversity and measured productivity across Europe and North America.
Combining results across the 46 study sites, the researchers found that the higher the plant biodiversity, the lower the variability in productivity during wet or dry climate events. Overall, productivity of communities with only one or two species changed an average of 50 percent during events, while those with 16 to 32 species changed only half that much. Biodiversity did not, however, seem to strongly influence how quickly a site returned to normal productivity after wet or dry events.
Our results suggest that biodiversity mainly stabilizes ecosystem productivity, and productivity-dependent ecosystem services, by increasing resistance to climate events. Anthropogenic environmental changes that drive biodiversity loss thus seem likely to decrease ecosystem stability, and restoration of biodiversity to increase it, mainly by changing the resistance of ecosystem productivity to climate events.