Exploring the Relationship Between Socioeconomic Inequality and Threatened Species

I finally got around to reading this study from PLoS One, another paper trying to address socioeconomic influences on ecology and biodiversity. The researchers explored a possible correlation between economic inequality - the distribution of wealth - and biodiversity in the US (state by state) and several other countries.

They used the Gini coefficient for measuring economic inequality. Gini coefficients are expressed in a scale from 0 to 1.0, with 0 being an area in which all families/households earn exactly the same income (perfect equality) and 1.0 being an area in which one family earns all of the income (perfect inequality). For reference, among the 45 US states chosen by the researchers for the study, which collectively make up 91% of the land and 97% of the US population, the Gini coefficient ranged from 0.31 to 0.53. Controls were also in place to consider the disparity between the value of money in different states/countries, using GDP PPP (gross domestic product purchasing power parity - "each dollar buys an equivalent amount of goods or services" across the board). Also, a time lag for impact was integrated, taking into account that socioeconomic factors would not immediately affect an area.

The results confirmed their suspicions. In both cases, US states and selected countries, a "striking" correlation was observed between economic inequality and reduced biodiversity, as shown by the following graph.

(A) Number of threatened plant and vertebrate species across countries; the curve shows the best-fit bi-variate power relationship. (B) Number of declining permanent resident bird species across US states; the line shows the best-fit bi-variate linear relationship. Of the apparent outliers in both Figure 1A and 1B, only those identified in the course of the multi-variate analyses described in the text are labeled.

Prediction is key. Among the country level data, the researchers found that a 1% increase in the Gini coefficient corresponds with a 2% rise in threatened plants and animals, in general. In 2012 the US may see a correlative 9% increase in threatened species due to a 5% increase in the Gini ratio from 1989 to 1997.

The hope here is that this study will be the first of many acknowledging and addressing the effects social institutions have on ecological matters. In 2007, it is probably safe to say that there is no such thing as a natural or pristine ecology.

"With biodiversity loss, if we don't link the science to the social causes, we will never solve the problem," co-author Dr. Andrew Gonzalez told PLoS.

The next step? Finding the exactly mechanism(s) of this relationship.