Human Life Span Linked To Endangered Species
October 10, 2013

Longer Life Spans For Humans Linked To Loss Of Biodiversity

April Flowers for - Your Universe Online

A new study from the University of California, Davis reveals that as human life expectancy increases, so does the number of endangered and invasive bird and mammal species.

The research team examined a combination of 15 social and ecological variables, ranging from tourism and per capita gross domestic product to water stress and political stability, then analyzed the correlations with invasive and endangered birds and mammals, which are two indicators of what conservationist Aldo Leopold termed "land sickness." The findings were published in a recent issue of Ecology and Society.

Researchers rarely include human life expectancy among the indexes that examine human impacts on the environment. In the current study, however, human life expectancy surfaced as the key predictor of global invasions and extinctions.

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

Data from 100 countries - including roughly 87 percent of the world's population, 43 percent of the world's GPD per capita, and covering 74 percent of the Earth's total land area - were analyzed for the study. The team also incorporated agricultural intensity, rainfall, pesticide regulation, energy efficiency, wilderness protection, latitude, export-import ratio, undernourishment, adult literacy, female participation in government, and total population.

Some of the study's most salient findings included the following:

  • The highest percentages of endangered and invasive birds were found in New Zealand, the US and the Philippines.
  • Largely due to its lack of native terrestrial mammals, New Zealand had the highest percentage of all endangered and invasive species combined. In the 700 to 800 years since the country was colonized, a catastrophic biodiversity loss has been caused by massive invasion of non-indigenous species.
  • The lowest percentage of invasive and endangered birds and mammals were found in African countries, which have had very little international trade. This limits opportunities for biological invasion.
  • The percentage of invasive bird and mammals in a country increased as the GPD - a standard measure of affluence - increased.
  • The percentage of endangered birds in a country increased as the total biodiversity and total land area also increased. In this context, biodiversity is not a measure of health, but of the number of species in an area.

The results indicate the need for a better scientific understanding of the complex interactions among humans and their environment, according to Lotz.

"Some studies have this view that there's wildlife and then there's us," said Lotz. "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."