Dung beetles increase plant growth: A meta-analysis

The ecosystem services provided by dung beetles are well-known and valued.
Dung beetles bury dung for feeding and breeding, and it is generally
thought that the process of burying dung increases nutrient uptake by
plant roots, which promotes plant growth. Many studies have tested the
effects of dung beetles on plant growth, but there has been no
quantitative synthesis of these studies. Here we use a multi-level
meta-analysis to estimate the average effect of dung beetles on plant
growth and investigate factors that moderate this effect. We identified 28
publications that investigated dung beetle effects on plant growth. Of
these, 24 contained the minimum quantitative data necessary to include in
a meta-analysis. Overall, we found that dung beetles increased plant
growth by 17 %; the 95 % CI for possible values for the true increase in
plant growth that were most compatible with our data, given our
statistical model, ranged from 1 to 35 %. We found evidence that the dung
beetle–plant growth relationship is influenced by the plant measurement
type and the number of beetles accessing the dung. However, beetles did
not increase plant growth in all quantitative trials, as individual effect
sizes ranged from -72 % – 806 %, suggesting important context-dependence
in the provision of ecosystem services.