Indicators provide warnings that risks may be about to crystallise. Single indicators can provide information on complex systems or scenarios if chosen correctly, but they do need to be checked for validity.
Dung beetles have been monitored for years as indicators for complex eco-systems. Their numbers can provide an indicator of the impact of activities such as logging, grazing and road building. When there are abundant species of dung beetle around and animal faeces disappear rapidly, then the ecosystem is in good health; otherwise, something is wrong. An Oxford University zoologist has recently shown that these monitoring methods, and thus the indicators reported, may be flawed.
Sampling is generally done by attracting dung beetles with faeces, and researchers have usually used their own as bait. The zoologist realised that this method had never been tested, so she set up a study in the Brazilian tropical forest comparing the results using both the dung of various forest animals versus human faeces, her own. The results using human faeces indicated twice the number of dung beetles and much greater diversity of species. This was just one test, but it shows that past monitoring activities may have been overstating the health of the ecosystems they were measuring.
And no-one yet knows why dung beetles seem to prefer human faeces…
Data Source: The Economist magazine