As human life expectancy increases, so does the percentage ofinvasive and endangered birds and mammals, according to a new studyby the University of California, Davis.
The study, published in the September issue of Ecology and Society,examined a combination of 15 social and ecological variables -- fromtourism and per capita gross domestic product to water stress andpolitical stability. Then researchers analyzed their correlationswith invasive and endangered birds and mammals, which are twoindicators of what conservationist Aldo Leopold termed "landsickness," the study said.
Human life expectancy, which is rarely included among indexes thatexamine human impacts on the environment, surfaced as the keypredictor of global invasions and extinctions.
"It's not a random pattern," said lead author Aaron Lotz, apostdoctoral scholar in the Department of Wildlife, Fish andConservation Biology when the study was conducted. "Out of all thisdata, that one factor -- human life expectancy -- was the determiningfactor for endangered and invasive birds and mammals."
The study analyzed data from 100 countries, which included roughly 87percent of the world's population, 43 percent of global GDP percapita, and covered 74 percent of the Earth's total land area.Additional factors considered were agricultural intensity, rainfall,pesticide regulation, energy efficiency, wilderness protection,latitude, export-import ratio, undernourishment, adult literacy,female participation in government, and total population.
The findings include:
- New Zealand, the United States and the Philippines had among thehighest percentages of endangered and invasive birds.
- New Zealand had the highest percentage of all endangered andinvasive species combined, largely due to its lack of nativeterrestrial mammals. The study said that in the past 700 to 800 yearssince the country was colonized, it has experienced massive invasionby nonindigenous species, resulting in catastrophic biodiversity loss.
- African countries had the lowest percentage of invasive andendangered birds and mammals. These countries have had very littleinternational trade, which limits opportunities for biologicalinvasion.
- As GDP per capita -- a standard measure of affluence -- increased ina country, so did the percentage of invasive birds and mammals.
- As total biodiversity and total land area increased in a country,so did the percentage of endangered birds. (Biodiversity in thiscontext is not a measure of health but refers to the number ofspecies in an area.)
Lotz said the study's results indicate the need for a betterscientific understanding of the complex interactions among humans andtheir environment.
"Some studies have this view that there's wildlife and then there'sus," said Lotz. "But we're part of the ecosystem. We need to startrelating humans to the environment in our research and not leave themout of the equation. We need to realize we have a direct link tonature."
Source: University of California - Davis