Increasing Inequality Threatens Biodiversity
29 May, 2007 07:30 pm
Biodiversity?the great variety of populations, species, and ecosystems?is now being eroded at a rate not seen since the last mass extinction some 65 million years ago, and there is concern that this loss may threaten human welfare.
Previous research has shown that the size and productivity of a country’s economy predicts how big its ‘footprint’ will be on the environment. This makes sense because productive and fast growing economies invest heavily in resource extraction and create a great deal of waste, both of which negatively impact the environment. However, the wealth and improvements in the standard of living associated with modern economies are often inequitably distributed amongst the population. There is great variability in the level of economic equality amongst countries, just as there are big differences in levels of biodiversity loss. In addition rising inequality is one of the major concerns associated with current globalization. Does the distribution of wealth generated by an economy affect the impact of a country on its biodiversity? Our study sought to answer this question.
To answer this question we obtained the best available data on the number of plant and vertebrate species threatened with extinction in 2004 in 45 different countries from around the world. We then obtained data on the level of income inequality amongst households within those same countries over the period from 1960 to 1999. Because the impacts of any economy on the environment, and hence on biodiversity, are not immediate, and may involve a delay, we correlated economic inequality in 1989 with the number of threatened species in 2004; this 25 year delay although initially a ‘best guess’ turned out to be the best supported by the data. Our statistical analysis revealed a strong positive correlation between income inequality and the number of threatened species in a country—countries with relatively high levels of inequality like Mexico or the United States have relatively large numbers of threatened species. This correlation was best described by an accelerating curve, and not a straight line, that when translated in terms of percentages suggests that a 1% increase in inequality is associated with a nearly 2% in the number of threatened species. Of course other factors, like human population size, the productivity of a country’s economy (e.g. the gross domestic product), and the total numbers of species are to be linked to the number of threatened species within a country. So to be sure that these factors did not interfere with our results we incorporated them into our analysis. When this was done our analysis still revealed the same striking relationship between inequality and the number of threatened species. To gain further confidence in our result we tested whether the same relationship could be found at the scale of a single country.
The best data for this analysis comes from the United States where family income inequality data are available for each state, and excellent records of change in the abundances of permanent resident bird species for each state also goes back 40 years. The same statistical analysis also revealed a positive correlation between family income inequality (in 1969) and the number of declining bird species over the last 40 years—U.S states with relatively high inequality, like Texas, have a greater number of declining bird species. The result reinforces our confidence in the veracity of the relationship between economic inequality and biodiversity loss.
These new findings raise important questions that we did not address in our study. For example, why does inequality bring about an increase in the number of threatened species? The answer to this question is likely to be complex and involve many social, economic and ecological processes that operate both at the scale of local communities and at the scale of nation states. These questions are the subject of continued research, and further reflections on why inequality creates biodiversity loss must await further analysis.
If further research does confirm clear causal relationships between economic inequality and biodiversity loss it may help us to predict future impacts of rising inequality. For example, our results suggest that the 5% increase in inequality observed in the US from 1989 to 1997 could translate into a nearly 9% increase in the number threatened plant and vertebrate species by 2012. The implication is that if current trends toward greater inequality are not reversed, it may become increasingly hard to prevent the steady rise in species extinction rates predicted for the coming century. More optimistically this research suggests that “if we can learn share economic resources more fairly with our own species, it may help us to share ecological resources more fairly with our fellow species” Mikkelson et al. (2007).
Mikkelson, G.M., et al. (2007) Economic Inequality Predicts Biodiversity loss. PLoS ONE 2(5): e444.doi:10.1371/journal.pone.0000444