Human Life Expectancy Affects Endangered Species

A latest finding highlights a strong association between increased human life expectancy and global invasions and extinctions of endangered species.

The study conducted by researchers at the University of California Davis suggests that, as human life expectancy increases, so does the percentage of invasive and endangered birds and mammals. The researchers provided a conclusion after analyzing 100 countries that has 87 percent of the world population, 74 percent of the Earth's land area and 43 percent of the global GDP per capita, according to press release.

On completing the analysis the researchers concluded that human life expectancy is a key predictor of global invasions and extinctions.

"It's not a random pattern," lead author Aaron Lotz, a postdoctoral scholar in the Department of Wildlife, Fish and Conservation Biology, said in a statement. "Out of all this data, that one factor - human life expectancy - was the determining factor for endangered and invasive birds and mammals."

For the study, they examined a mixture of 15 social and ecological variables that included water stress, political stability, tourism and per capita gross domestic product. Then researchers analyzed their association with both invasive and endangered birds and mammals, as these two are indicators of what is termed as  'land sickness' by conservationist Also Leopold. The additional factors the study included were rainfall, energy efficiency, latitude, adult literacy,  pesticide regulation, agricultural intensity, participation of female in government, export-import ratio, undernourishment and total population.

The research team noticed that New Zealand, Philippines and the U.S. consisted of highest percentages of endangered as well as invasive birds. A highest percentage of endangered and invasive species together was present in New Zealand. The country has also suffered a catastrophic biodiversity loss as in the past 700-800 years ever since the country was colonized it faced a massive invasion of non indigenous species.

On the other hand, the lowest percentage of invasive and endangered birds and mammals was present in African countries, the reason given by scientists was that these countries also had extremely less international trade that limits the opportunity for biological invasion.

Increase in GDP per Captia in the country led to a simultaneous increase in the percentage of invasive birds and mammals. The percentage of endangered birds increased as the total biodiversity and the total land area in the country increased. The scientists explain that biodiversity in the study was seen as the number of species in the area

This finding demands a further scientific understanding of the complex interactions talking place among humans and their environment.

Lotz concluded saying, "Some studies have this view that there's wildlife and then there's us. But we're part of the ecosystem. We need to start relating humans to the environment in our research and not leave them out of the equation. We need to realize we have a direct link to nature."

The finding was published in the journal Ecology and Society.