Most human beings are aware of the common threats to biodiversity such as pollution and climate change, but a recent dark horse has emerged. As human life expectancy increases, the percentage of invasive and endangered species suffers a similar surge, according to a new study by the University of California, Davis.
Gathering data from 100 countries comprising 87% of the world’s population, the study analyzed fifteen socio-ecological variables ranging from gross domestic product and life expectancy to adult literacy and political stability. Consequently, relationships found between these independent variables and the health of endangered and invasive species have global importance.
By utilizing endangered and invasive birds and mammals as dependent variables, researchers can assess the “land sickness”, a term coined by conservationist Aldo Leopold.
Above all, human life expectancy emerged as the primary indicator of global extinctions and invasions, contributing heavily to the current “land sickness” crisis.
Increased life expectancy signifies that people live longer and therefore have more opportunities to affect the planet through additional means; each year is another year of carbon footprints, ecological footprints, and natural resource abuse.
The magnitude of this impact is compounded as more people live longer.
Although human life expectancy is often ignored as an index of human impact on the environment, the authors suggest that it should be considered a major influence.
According to lead author Aaron Lotz, “Out of all this data, that one factor – human life expectancy – was the determining factor for endangered and invasive birds and mammals.”
Lotz also asserts that changes in biodiversity because of human have been more profound in the last 50 years than in the whole prior recorded history. He corroborates this claim through the fact that “52% of cycads, 32% of amphibians, 25% of conifers, 23% of mammals, and 12% of bird species are currently threatened with extinction.”
From these devastating numbers, it should come as no surprise that “life expectancy at birth has increased globally by 6 years since 1990,” as stated by the World Health Organization.
Other factors considered such as gross domestic product, tourism, export-import ratio, undernourishment, agricultural intensity, rainfall, water stress, wilderness protection, total biodiversity, pesticide regulation, and female participation have also provided significant impacts on the current state of endangered and invasive species.
For example, as GDP per capita increases, so does the percentage of invasive birds. Countries like the United States, New Zealand, and Australia currently report the highest percentages of invasive birds.
On the other hand, of the 26 countries analyzed in the Africa region, 23 were included in the top 25 for countries with the lowest percentages of invasive and endangered birds and mammals. Since these countries have a closed trade policy, they circumvented the opportunities for biological invasion that come with international trade.
Although the study recognizes important patterns in the global social-ecological system, it does not provide insight into the mechanisms that perpetuate these situations. Now that the problem is identified, action must be taken to ameliorate these startling circumstances.
While we may enjoy longer life expectancies now, the quality of life decreases as our contributions to environmental degradation create an increasingly uninhabitable planet.
1. Lotz, A., and C. R. Allen. 2013. Social-ecological predictors of global invasions and extinctions. Ecology and Society 18(3): 15. http://dx.doi.org/10.5751/ES-05550-180315
3. Photograph: http://www.dijitalimaj.com/alamyDetail.aspx?img=%7B8AF8BEF0-56B8-4F5D-9469-DC3E7BC84B91%7D)