Stuck in the 1950s: Distributions of soil bacteria lag up to 60 years behind anthropogenic climate change

Background/Question/Methods

Anthropogenic climate change is disrupting many ecological communities, and these disruptions are expected to increase as climate change intensifies. Soil bacteria play a key role in many terrestrial ecosystems, being the cornerstones of trophic interactions, biogeochemical cycles, and ecosystem services. Experimentation in model systems suggests that soil bacterial communities will quickly respond to climate change, with community adaptation occurring within hours to days, and that there will be few irreversible effects of climate change, such as extinctions, in soil bacterial communities.  Here, we test these predictions using 16S rRNA sequence data from bacterial communities across Tibet and North America and climate records spanning 1950 to 2012.

Results/Conclusions

Surprisingly, we find that the current distributions of major taxa of bacteria in soil across Tibet (180 communities) and North America (80 communities) are better predicted by the climate from 10 to 60 years ago than by the contemporary climate; thus the distributions of bacteria lag behind shifts in climate. We find similar lags with climate when examining the distributions of bacterial richness and evenness. The climate from 1950 to 1960 is particularly predictive for many taxa and measures of diversity. We find that the lags are most pronounced within regions that have experienced anthropogenic climate change, but largely absent in regions where climate remains near historical levels. Hence, the lags may be due to the inability of soil bacteria to keep up with anthropogenic climate change. Using niche modeling, we project how much bacterial distributions would change if bacteria were able to catch up with contemporary climate. This modeling indicates widespread shifts in communities and decreases in diversity. Contrary to current understanding, our results suggest that soil bacteria may not be able to shift their ranges fast enough to accommodate anthropogenic shifts in climate, with the consequence that climate change may have lasting and unexpected impacts on microbial biodiversity.